Merge pull request #1295 from alexcrichton/js-snippets

Implement the local JS snippets RFC

Cargo.toml

@@ -81,6 +81,7 @@ members = [
   "examples/webaudio",
   "examples/webgl",
   "examples/without-a-bundler",
+  "examples/without-a-bundler-no-modules",
   "tests/no-std",
 ]
 exclude = ['crates/typescript']

azure-pipelines.yml

@@ -40,10 +40,15 @@ jobs:
       - template: ci/azure-install-sccache.yml
       - script: cargo test --target wasm32-unknown-unknown
         displayName: "wasm-bindgen test suite"
+        env:
+          RUST_LOG: wasm_bindgen_test_runner
+          GECKODRIVER_ARGS: --log trace
       - script: cargo test --target wasm32-unknown-unknown -p js-sys
         displayName: "js-sys test suite"
       - script: cargo test --target wasm32-unknown-unknown -p webidl-tests
         displayName: "webidl-tests test suite"
+        env:
+          WBINDGEN_I_PROMISE_JS_SYNTAX_WORKS_IN_NODE: 1
       - script: cargo build --manifest-path crates/web-sys/Cargo.toml --target wasm32-unknown-unknown --features "Node Window Document"
         displayName: "web-sys build"
 
@@ -94,6 +99,8 @@ jobs:
       - template: ci/azure-install-sccache.yml
       - script: cargo test -p wasm-bindgen-webidl
       - script: cargo test -p webidl-tests --target wasm32-unknown-unknown
+        env:
+          WBINDGEN_I_PROMISE_JS_SYNTAX_WORKS_IN_NODE: 1
 
   - job: test_ui
     displayName: "Run UI tests"

ci/azure-install-geckodriver.yml

@@ -12,3 +12,14 @@ steps:
       Write-Host "##vso[task.setvariable variable=GECKODRIVER;]$pwd\geckodriver.exe"
     displayName: "Download Geckodriver (Windows)"
     condition: eq( variables['Agent.OS'], 'Windows_NT' )
+
+  # It turns out that geckodriver.exe will fail if firefox takes too long to
+  # start, and for whatever reason the first execution of `firefox.exe` can
+  # take upwards of a mimute. It seems that subsequent executions are much
+  # faster, so have a dedicated step to run Firefox once which should I
+  # guess warm some cache somewhere so the headless tests later on all
+  # finish successfully
+  - script: |
+      "C:\Program Files\Mozilla Firefox\firefox.exe" --version
+    displayName: "Load firefox.exe into cache (presumably?)"
+    condition: eq( variables['Agent.OS'], 'Windows_NT' )

crates/backend/Cargo.toml

@@ -15,6 +15,7 @@ spans = []
 extra-traits = ["syn/extra-traits"]
 
 [dependencies]
+bumpalo = "2.1"
 lazy_static = "1.0.0"
 log = "0.4"
 proc-macro2 = "0.4.8"

crates/backend/src/ast.rs

@@ -2,6 +2,7 @@ use proc_macro2::{Ident, Span};
 use shared;
 use syn;
 use Diagnostic;
+use std::hash::{Hash, Hasher};
 
 /// An abstract syntax tree representing a rust program. Contains
 /// extra information for joining up this rust code with javascript.
@@ -24,6 +25,8 @@ pub struct Program {
     pub dictionaries: Vec<Dictionary>,
     /// custom typescript sections to be included in the definition file
     pub typescript_custom_sections: Vec<String>,
+    /// Inline JS snippets
+    pub inline_js: Vec<String>,
 }
 
 /// A rust to js interface. Allows interaction with rust objects/functions
@@ -66,11 +69,37 @@ pub enum MethodSelf {
 #[cfg_attr(feature = "extra-traits", derive(Debug, PartialEq, Eq))]
 #[derive(Clone)]
 pub struct Import {
-    pub module: Option<String>,
+    pub module: ImportModule,
     pub js_namespace: Option<Ident>,
     pub kind: ImportKind,
 }
 
+#[cfg_attr(feature = "extra-traits", derive(Debug, PartialEq, Eq))]
+#[derive(Clone)]
+pub enum ImportModule {
+    None,
+    Named(String, Span),
+    Inline(usize, Span),
+}
+
+impl Hash for ImportModule {
+    fn hash<H: Hasher>(&self, h: &mut H) {
+        match self {
+            ImportModule::None => {
+                0u8.hash(h);
+            }
+            ImportModule::Named(name, _) => {
+                1u8.hash(h);
+                name.hash(h);
+            }
+            ImportModule::Inline(idx, _) => {
+                2u8.hash(h);
+                idx.hash(h);
+            }
+        }
+    }
+}
+
 #[cfg_attr(feature = "extra-traits", derive(Debug, PartialEq, Eq))]
 #[derive(Clone)]
 pub enum ImportKind {

crates/backend/src/codegen.rs

@@ -94,25 +94,45 @@ impl TryToTokens for ast::Program {
             shared::SCHEMA_VERSION,
             shared::version()
         );
+        let encoded = encode::encode(self)?;
         let mut bytes = Vec::new();
         bytes.push((prefix_json.len() >> 0) as u8);
         bytes.push((prefix_json.len() >> 8) as u8);
         bytes.push((prefix_json.len() >> 16) as u8);
         bytes.push((prefix_json.len() >> 24) as u8);
         bytes.extend_from_slice(prefix_json.as_bytes());
-        bytes.extend_from_slice(&encode::encode(self)?);
+        bytes.extend_from_slice(&encoded.custom_section);
 
         let generated_static_length = bytes.len();
         let generated_static_value = syn::LitByteStr::new(&bytes, Span::call_site());
 
+        // We already consumed the contents of included files when generating
+        // the custom section, but we want to make sure that updates to the
+        // generated files will cause this macro to rerun incrementally. To do
+        // that we use `include_str!` to force rustc to think it has a
+        // dependency on these files. That way when the file changes Cargo will
+        // automatically rerun rustc which will rerun this macro. Other than
+        // this we don't actually need the results of the `include_str!`, so
+        // it's just shoved into an anonymous static.
+        let file_dependencies = encoded.included_files
+            .iter()
+            .map(|file| {
+                let file = file.to_str().unwrap();
+                quote! { include_str!(#file) }
+            });
+
         (quote! {
             #[allow(non_upper_case_globals)]
             #[cfg(target_arch = "wasm32")]
             #[link_section = "__wasm_bindgen_unstable"]
             #[doc(hidden)]
             #[allow(clippy::all)]
-            pub static #generated_static_name: [u8; #generated_static_length] =
-                *#generated_static_value;
+            pub static #generated_static_name: [u8; #generated_static_length] = {
+                static _INCLUDED_FILES: &[&str] = &[#(#file_dependencies),*];
+
+                *#generated_static_value
+            };
+
         })
         .to_tokens(tokens);
 

crates/backend/src/encode.rs

@@ -1,40 +1,96 @@
+use proc_macro2::{Ident, Span};
 use std::cell::RefCell;
 use std::collections::HashMap;
-
-use proc_macro2::{Ident, Span};
+use std::env;
+use std::fs;
+use std::path::PathBuf;
+use util::ShortHash;
 
 use ast;
 use Diagnostic;
 
-pub fn encode(program: &ast::Program) -> Result<Vec<u8>, Diagnostic> {
+pub struct EncodeResult {
+    pub custom_section: Vec<u8>,
+    pub included_files: Vec<PathBuf>,
+}
+
+pub fn encode(program: &ast::Program) -> Result<EncodeResult, Diagnostic> {
     let mut e = Encoder::new();
     let i = Interner::new();
     shared_program(program, &i)?.encode(&mut e);
-    Ok(e.finish())
+    let custom_section = e.finish();
+    let included_files = i.files.borrow().values().map(|p| &p.path).cloned().collect();
+    Ok(EncodeResult { custom_section, included_files })
 }
 
 struct Interner {
-    map: RefCell<HashMap<Ident, String>>,
+    bump: bumpalo::Bump,
+    files: RefCell<HashMap<String, LocalFile>>,
+    root: PathBuf,
+    crate_name: String,
+}
+
+struct LocalFile {
+    path: PathBuf,
+    definition: Span,
+    new_identifier: String,
 }
 
 impl Interner {
     fn new() -> Interner {
         Interner {
-            map: RefCell::new(HashMap::new()),
+            bump: bumpalo::Bump::new(),
+            files: RefCell::new(HashMap::new()),
+            root: env::var_os("CARGO_MANIFEST_DIR").unwrap().into(),
+            crate_name: env::var("CARGO_PKG_NAME").unwrap(),
         }
     }
 
     fn intern(&self, s: &Ident) -> &str {
-        let mut map = self.map.borrow_mut();
-        if let Some(s) = map.get(s) {
-            return unsafe { &*(&**s as *const str) };
-        }
-        map.insert(s.clone(), s.to_string());
-        unsafe { &*(&*map[s] as *const str) }
+        self.intern_str(&s.to_string())
     }
 
     fn intern_str(&self, s: &str) -> &str {
-        self.intern(&Ident::new(s, Span::call_site()))
+        // NB: eventually this could be used to intern `s` to only allocate one
+        // copy, but for now let's just "transmute" `s` to have the same
+        // lifetmie as this struct itself (which is our main goal here)
+        bumpalo::collections::String::from_str_in(s, &self.bump).into_bump_str()
+    }
+
+    /// Given an import to a local module `id` this generates a unique module id
+    /// to assign to the contents of `id`.
+    ///
+    /// Note that repeated invocations of this function will be memoized, so the
+    /// same `id` will always return the same resulting unique `id`.
+    fn resolve_import_module(&self, id: &str, span: Span) -> Result<&str, Diagnostic> {
+        let mut files = self.files.borrow_mut();
+        if let Some(file) = files.get(id) {
+            return Ok(self.intern_str(&file.new_identifier))
+        }
+        let path = if id.starts_with("/") {
+            self.root.join(&id[1..])
+        } else if id.starts_with("./") || id.starts_with("../") {
+            let msg = "relative module paths aren't supported yet";
+            return Err(Diagnostic::span_error(span, msg))
+        } else {
+            return Ok(self.intern_str(&id))
+        };
+
+        // Generate a unique ID which is somewhat readable as well, so mix in
+        // the crate name, hash to make it unique, and then the original path.
+        let new_identifier = format!("{}{}", self.unique_crate_identifier(), id);
+        let file = LocalFile {
+            path,
+            definition: span,
+            new_identifier,
+        };
+        files.insert(id.to_string(), file);
+        drop(files);
+        self.resolve_import_module(id, span)
+    }
+
+    fn unique_crate_identifier(&self) -> String {
+        format!("{}-{}", self.crate_name, ShortHash(0))
     }
 }
 
@@ -64,8 +120,30 @@ fn shared_program<'a>(
             .iter()
             .map(|x| -> &'a str { &x })
             .collect(),
-        // version: shared::version(),
-        // schema_version: shared::SCHEMA_VERSION.to_string(),
+        local_modules: intern
+            .files
+            .borrow()
+            .values()
+            .map(|file| {
+                fs::read_to_string(&file.path)
+                    .map(|s| {
+                        LocalModule {
+                            identifier: intern.intern_str(&file.new_identifier),
+                            contents: intern.intern_str(&s),
+                        }
+                    })
+                    .map_err(|e| {
+                        let msg = format!("failed to read file `{}`: {}", file.path.display(), e);
+                        Diagnostic::span_error(file.definition, msg)
+                    })
+            })
+            .collect::<Result<Vec<_>, _>>()?,
+        inline_js: prog
+            .inline_js
+            .iter()
+            .map(|js| intern.intern_str(js))
+            .collect(),
+        unique_crate_identifier: intern.intern_str(&intern.unique_crate_identifier()),
     })
 }
 
@@ -111,7 +189,13 @@ fn shared_variant<'a>(v: &'a ast::Variant, intern: &'a Interner) -> EnumVariant<
 
 fn shared_import<'a>(i: &'a ast::Import, intern: &'a Interner) -> Result<Import<'a>, Diagnostic> {
     Ok(Import {
-        module: i.module.as_ref().map(|s| &**s),
+        module: match &i.module {
+            ast::ImportModule::Named(m, span) => {
+                ImportModule::Named(intern.resolve_import_module(m, *span)?)
+            }
+            ast::ImportModule::Inline(idx, _) => ImportModule::Inline(*idx as u32),
+            ast::ImportModule::None => ImportModule::None,
+        },
         js_namespace: i.js_namespace.as_ref().map(|s| intern.intern(s)),
         kind: shared_import_kind(&i.kind, intern)?,
     })

crates/backend/src/lib.rs

@@ -2,6 +2,7 @@
 #![cfg_attr(feature = "extra-traits", deny(missing_debug_implementations))]
 #![doc(html_root_url = "https://docs.rs/wasm-bindgen-backend/0.2")]
 
+extern crate bumpalo;
 #[macro_use]
 extern crate log;
 extern crate proc_macro2;

crates/backend/src/util.rs

@@ -94,7 +94,7 @@ pub fn ident_ty(ident: Ident) -> syn::Type {
 
 pub fn wrap_import_function(function: ast::ImportFunction) -> ast::Import {
     ast::Import {
-        module: None,
+        module: ast::ImportModule::None,
         js_namespace: None,
         kind: ast::ImportKind::Function(function),
     }

crates/cli-support/src/js/mod.rs

@@ -1,8 +1,9 @@
 use crate::decode;
 use crate::descriptor::{Descriptor, VectorKind};
-use crate::{Bindgen, EncodeInto};
+use crate::{Bindgen, EncodeInto, OutputMode};
 use failure::{bail, Error, ResultExt};
 use std::collections::{HashMap, HashSet};
+use std::env;
 use walrus::{MemoryId, Module};
 use wasm_bindgen_wasm_interpreter::Interpreter;
 
@@ -33,7 +34,7 @@ pub struct Context<'a> {
     /// from, `None` being the global module. The second key is a map of
     /// identifiers we've already imported from the module to what they're
     /// called locally.
-    pub imported_names: HashMap<Option<&'a str>, HashMap<&'a str, String>>,
+    pub imported_names: HashMap<ImportModule<'a>, HashMap<&'a str, String>>,
 
     /// A set of all imported identifiers to the number of times they've been
     /// imported, used to generate new identifiers.
@@ -53,6 +54,16 @@ pub struct Context<'a> {
     pub interpreter: &'a mut Interpreter,
     pub memory: MemoryId,
 
+    /// A map of all local modules we've found, from the identifier they're
+    /// known as to their actual JS contents.
+    pub local_modules: HashMap<&'a str, &'a str>,
+
+    /// A map of how many snippets we've seen from each unique crate identifier,
+    /// used to number snippets correctly when writing them to the filesystem
+    /// when there's multiple snippets within one crate that aren't all part of
+    /// the same `Program`.
+    pub snippet_offsets: HashMap<&'a str, usize>,
+
     pub anyref: wasm_bindgen_anyref_xform::Context,
 }
 
@@ -100,6 +111,20 @@ enum Import<'a> {
         name: &'a str,
         field: Option<&'a str>,
     },
+    /// Same as `Module`, except we're importing from a local module defined in
+    /// a local JS snippet.
+    LocalModule {
+        module: &'a str,
+        name: &'a str,
+        field: Option<&'a str>,
+    },
+    /// Same as `Module`, except we're importing from an `inline_js` attribute
+    InlineJs {
+        unique_crate_identifier: &'a str,
+        snippet_idx_in_crate: usize,
+        name: &'a str,
+        field: Option<&'a str>,
+    },
     /// A global import which may have a number of vendor prefixes associated
     /// with it, like `webkitAudioPrefix`. The `name` is the name to test
     /// whether it's prefixed.
@@ -124,28 +149,62 @@ impl<'a> Context<'a> {
             self.globals.push_str(c);
             self.typescript.push_str(c);
         }
-        let global = if self.use_node_require() {
-            if contents.starts_with("class") {
-                format!("{1}\nmodule.exports.{0} = {0};\n", name, contents)
-            } else {
-                format!("module.exports.{} = {};\n", name, contents)
+        let global = match self.config.mode {
+            OutputMode::Node {
+                experimental_modules: false,
+            } => {
+                if contents.starts_with("class") {
+                    format!("{1}\nmodule.exports.{0} = {0};\n", name, contents)
+                } else {
+                    format!("module.exports.{} = {};\n", name, contents)
+                }
             }
-        } else if self.config.no_modules {
-            if contents.starts_with("class") {
-                format!("{1}\n__exports.{0} = {0};\n", name, contents)
-            } else {
-                format!("__exports.{} = {};\n", name, contents)
+            OutputMode::NoModules { .. } => {
+                if contents.starts_with("class") {
+                    format!("{1}\n__exports.{0} = {0};\n", name, contents)
+                } else {
+                    format!("__exports.{} = {};\n", name, contents)
+                }
             }
-        } else {
-            if contents.starts_with("function") {
-                format!("export function {}{}\n", name, &contents[8..])
-            } else if contents.starts_with("class") {
-                format!("export {}\n", contents)
-            } else {
-                format!("export const {} = {};\n", name, contents)
+            OutputMode::Bundler
+            | OutputMode::Node {
+                experimental_modules: true,
+            } => {
+                if contents.starts_with("function") {
+                    format!("export function {}{}\n", name, &contents[8..])
+                } else if contents.starts_with("class") {
+                    format!("export {}\n", contents)
+                } else {
+                    format!("export const {} = {};\n", name, contents)
+                }
+            }
+            OutputMode::Browser => {
+                // In browser mode there's no need to export the internals of
+                // wasm-bindgen as we're not using the module itself as the
+                // import object but rather the `__exports` map we'll be
+                // initializing below.
+                let export = if name.starts_with("__wbindgen")
+                    || name.starts_with("__wbg_")
+                    || name.starts_with("__widl_")
+                {
+                    ""
+                } else {
+                    "export "
+                };
+                if contents.starts_with("function") {
+                    format!("{}function {}{}\n", export, name, &contents[8..])
+                } else if contents.starts_with("class") {
+                    format!("{}{}\n", export, contents)
+                } else {
+                    format!("{}const {} = {};\n", export, name, contents)
+                }
             }
         };
         self.global(&global);
+
+        if self.config.mode.browser() {
+            self.global(&format!("__exports.{} = {0};", name));
+        }
     }
 
     fn require_internal_export(&mut self, name: &'static str) -> Result<(), Error> {
@@ -166,6 +225,170 @@ impl<'a> Context<'a> {
     }
 
     pub fn finalize(&mut self, module_name: &str) -> Result<(String, String), Error> {
+        // Wire up all default intrinsics, those which don't have any sort of
+        // dependency on the clsoure/anyref/etc passes. This is where almost all
+        // intrinsics are wired up.
+        self.wire_up_initial_intrinsics()?;
+
+        // Next up, perform our closure rewriting pass. This is where we'll
+        // update invocations of the closure intrinsics we have to instead call
+        // appropriate JS functions which actually create closures.
+        closures::rewrite(self).with_context(|_| "failed to generate internal closure shims")?;
+
+        // Finalize all bindings for JS classes. This is where we'll generate JS
+        // glue for all classes as well as finish up a few final imports like
+        // `__wrap` and such.
+        self.write_classes()?;
+
+        // And now that we're almost ready, run the final "anyref" pass. This is
+        // where we transform a wasm module which doesn't actually use `anyref`
+        // anywhere to using the type internally. The transformation here is
+        // based off all the previous data we've collected so far for each
+        // import/export listed.
+        self.anyref.run(self.module)?;
+
+        // With our transforms finished, we can now wire up the final list of
+        // intrinsics which may depend on the passes run above.
+        self.wire_up_late_intrinsics()?;
+
+        // We're almost done here, so we can delete any internal exports (like
+        // `__wbindgen_malloc`) if none of our JS glue actually needed it.
+        self.unexport_unused_internal_exports();
+
+        // Handle the `start` function, if one was specified. If we're in a
+        // --test mode (such as wasm-bindgen-test-runner) then we skip this
+        // entirely. Otherwise we want to first add a start function to the
+        // `start` section if one is specified.
+        //
+        // Note that once a start function is added, if any, we immediately
+        // un-start it. This is done because we require that the JS glue
+        // initializes first, so we execute wasm startup manually once the JS
+        // glue is all in place.
+        let mut needs_manual_start = false;
+        if self.config.emit_start {
+            self.add_start_function()?;
+            needs_manual_start = self.unstart_start_function();
+        }
+
+        // If our JS glue needs to access the function table, then do so here.
+        // JS closure shim generation may access the function table as an
+        // example, but if there's no closures in the module there's no need to
+        // export it!
+        self.export_table()?;
+
+        // After all we've done, especially
+        // `unexport_unused_internal_exports()`, we probably have a bunch of
+        // garbage in the module that's no longer necessary, so delete
+        // everything that we don't actually need.
+        walrus::passes::gc::run(self.module);
+
+        // Almost there, but before we're done make sure to rewrite the `module`
+        // field of all imports in the wasm module. The field is currently
+        // always `__wbindgen_placeholder__` coming out of rustc, but we need to
+        // update that here to the shim file or an actual ES module.
+        self.rewrite_imports(module_name);
+
+        // We likely made a ton of modifications, so add ourselves to the
+        // producers section!
+        self.update_producers_section();
+
+        // Cause any future calls to `should_write_global` to panic, making sure
+        // we don't ask for items which we can no longer emit.
+        drop(self.exposed_globals.take().unwrap());
+
+        Ok(self.finalize_js(module_name, needs_manual_start))
+    }
+
+    /// Performs the task of actually generating the final JS module, be it
+    /// `--no-modules`, `--browser`, or for bundlers. This is the very last step
+    /// performed in `finalize`.
+    fn finalize_js(&mut self, module_name: &str, needs_manual_start: bool) -> (String, String) {
+        let mut js = String::new();
+        if self.config.mode.no_modules() {
+            js.push_str("(function() {\n");
+        }
+
+        // Depending on the output mode, generate necessary glue to actually
+        // import the wasm file in one way or another.
+        let mut init = String::new();
+        match &self.config.mode {
+            // In `--no-modules` mode we need to both expose a name on the
+            // global object as well as generate our own custom start function.
+            OutputMode::NoModules { global } => {
+                js.push_str("const __exports = {};\n");
+                js.push_str("let wasm;\n");
+                init = self.gen_init(&module_name, needs_manual_start);
+                self.footer.push_str(&format!(
+                    "self.{} = Object.assign(init, __exports);\n",
+                    global
+                ));
+            }
+
+            // With normal CommonJS node we need to defer requiring the wasm
+            // until the end so most of our own exports are hooked up
+            OutputMode::Node {
+                experimental_modules: false,
+            } => {
+                self.footer
+                    .push_str(&format!("wasm = require('./{}_bg');\n", module_name));
+                if needs_manual_start {
+                    self.footer.push_str("wasm.__wbindgen_start();\n");
+                }
+                js.push_str("var wasm;\n");
+            }
+
+            // With Bundlers and modern ES6 support in Node we can simply import
+            // the wasm file as if it were an ES module and let the
+            // bundler/runtime take care of it.
+            OutputMode::Bundler
+            | OutputMode::Node {
+                experimental_modules: true,
+            } => {
+                js.push_str(&format!("import * as wasm from './{}_bg';\n", module_name));
+                if needs_manual_start {
+                    self.footer.push_str("wasm.__wbindgen_start();\n");
+                }
+            }
+
+            // With a browser-native output we're generating an ES module, but
+            // browsers don't support natively importing wasm right now so we
+            // expose the same initialization function as `--no-modules` as the
+            // default export of the module.
+            OutputMode::Browser => {
+                js.push_str("const __exports = {};\n");
+                self.imports_post.push_str("let wasm;\n");
+                init = self.gen_init(&module_name, needs_manual_start);
+                self.footer.push_str("export default init;\n");
+            }
+        }
+
+        // Emit all the JS for importing all our functionality
+        js.push_str(&self.imports);
+        js.push_str("\n");
+        js.push_str(&self.imports_post);
+        js.push_str("\n");
+
+        // Emit all our exports from this module
+        js.push_str(&self.globals);
+        js.push_str("\n");
+
+        // Generate the initialization glue, if there was any
+        js.push_str(&init);
+        js.push_str("\n");
+        js.push_str(&self.footer);
+        js.push_str("\n");
+        if self.config.mode.no_modules() {
+            js.push_str("})();\n");
+        }
+
+        while js.contains("\n\n\n") {
+            js = js.replace("\n\n\n", "\n\n");
+        }
+
+        (js, self.typescript.clone())
+    }
+
+    fn wire_up_initial_intrinsics(&mut self) -> Result<(), Error> {
         self.bind("__wbindgen_string_new", &|me| {
             me.anyref.import_xform(
                 "__wbindgen_placeholder__",
@@ -529,7 +752,7 @@ impl<'a> Context<'a> {
         })?;
 
         self.bind("__wbindgen_module", &|me| {
-            if !me.config.no_modules {
+            if !me.config.mode.no_modules() && !me.config.mode.browser() {
                 bail!(
                     "`wasm_bindgen::module` is currently only supported with \
                      --no-modules"
@@ -548,10 +771,28 @@ impl<'a> Context<'a> {
             ))
         })?;
 
-        closures::rewrite(self).with_context(|_| "failed to generate internal closure shims")?;
-        self.write_classes()?;
-        self.anyref.run(self.module)?;
+        self.bind("__wbindgen_throw", &|me| {
+            me.expose_get_string_from_wasm();
+            Ok(String::from(
+                "
+                function(ptr, len) {
+                    throw new Error(getStringFromWasm(ptr, len));
+                }
+                ",
+            ))
+        })?;
 
+        Ok(())
+    }
+
+    /// Provide implementations of remaining intrinsics after initial passes
+    /// have been run on the wasm module.
+    ///
+    /// The intrinsics implemented here are added very late in the process or
+    /// otherwise may be overwritten by passes (such as the anyref pass). As a
+    /// result they don't go into the initial list of intrinsics but go just at
+    /// the end.
+    fn wire_up_late_intrinsics(&mut self) -> Result<(), Error> {
         // After the anyref pass has executed, if this intrinsic is needed then
         // we expose a function which initializes it
         self.bind("__wbindgen_init_anyref_table", &|me| {
@@ -589,84 +830,12 @@ impl<'a> Context<'a> {
             Ok(String::from("function(i) { dropObject(i); }"))
         })?;
 
-        self.unexport_unused_internal_exports();
-
-        // Handle the `start` function, if one was specified. If we're in a
-        // --test mode (such as wasm-bindgen-test-runner) then we skip this
-        // entirely. Otherwise we want to first add a start function to the
-        // `start` section if one is specified.
-        //
-        // Afterwards, we need to perform what's a bit of a hack. Right after we
-        // added the start function, we remove it again because no current
-        // strategy for bundlers and deployment works well enough with it. For
-        // `--no-modules` output we need to be sure to call the start function
-        // after our exports are wired up (or most imported functions won't
-        // work).
-        //
-        // For ESM outputs bundlers like webpack also don't work because
-        // currently they run the wasm initialization before the JS glue
-        // initialization, meaning that if the wasm start function calls
-        // imported functions the JS glue isn't ready to go just yet.
-        //
-        // To handle `--no-modules` we just unstart the start function and call
-        // it manually. To handle the ESM use case we switch the start function
-        // to calling an imported function which defers the start function via
-        // `Promise.resolve().then(...)` to execute on the next microtask tick.
-        let mut has_start_function = false;
-        if self.config.emit_start {
-            self.add_start_function()?;
-            has_start_function = self.unstart_start_function();
-
-            // In the "we're pretending to be an ES module use case if we've got
-            // a start function then we use an injected shim to actually execute
-            // the real start function on the next tick of the microtask queue
-            // (explained above)
-            if !self.config.no_modules && has_start_function {
-                self.inject_start_shim();
-            }
-
-        }
-
-        self.export_table()?;
-
-        walrus::passes::gc::run(self.module);
-
-        // Note that it's important `throw` comes last *after* we gc. The
-        // `__wbindgen_malloc` function may call this but we only want to
-        // generate code for this if it's actually live (and __wbindgen_malloc
-        // isn't gc'd).
-        self.bind("__wbindgen_throw", &|me| {
-            me.expose_get_string_from_wasm();
-            Ok(String::from(
-                "
-                function(ptr, len) {
-                    throw new Error(getStringFromWasm(ptr, len));
-                }
-                ",
-            ))
-        })?;
-
-        self.rewrite_imports(module_name);
-        self.update_producers_section();
-
-        // Cause any future calls to `should_write_global` to panic, making sure
-        // we don't ask for items which we can no longer emit.
-        drop(self.exposed_globals.take().unwrap());
-
-        let mut js = if self.config.threads.is_some() {
-            // TODO: It's not clear right now how to best use threads with
-            // bundlers like webpack. We need a way to get the existing
-            // module/memory into web workers for now and we don't quite know
-            // idiomatically how to do that! In the meantime, always require
-            // `--no-modules`
-            if !self.config.no_modules {
-                bail!("most use `--no-modules` with threads for now")
-            }
-            let mem = self.module.memories.get(self.memory);
-            if mem.import.is_none() {
-                bail!("must impot a shared memory with threads")
-            }
+        Ok(())
+    }
 
+    fn gen_init(&mut self, module_name: &str, needs_manual_start: bool) -> String {
+        let mem = self.module.memories.get(self.memory);
+        let (init_memory1, init_memory2) = if mem.import.is_some() {
             let mut memory = String::from("new WebAssembly.Memory({");
             memory.push_str(&format!("initial:{}", mem.initial));
             if let Some(max) = mem.maximum {
@@ -676,158 +845,64 @@ impl<'a> Context<'a> {
                 memory.push_str(",shared:true");
             }
             memory.push_str("})");
-
-            format!(
-                "\
-(function() {{
-    var wasm;
-    var memory;
-    const __exports = {{}};
-    {globals}
-    function init(module_or_path, maybe_memory) {{
-        let result;
-        const imports = {{ './{module}': __exports }};
-        if (module_or_path instanceof WebAssembly.Module) {{
-            memory = __exports.memory = maybe_memory;
-            result = WebAssembly.instantiate(module_or_path, imports)
-                .then(instance => {{
-                    return {{ instance, module: module_or_path }}
-                }});
-        }} else {{
-            memory = __exports.memory = {init_memory};
-            const response = fetch(module_or_path);
-            if (typeof WebAssembly.instantiateStreaming === 'function') {{
-                result = WebAssembly.instantiateStreaming(response, imports)
-                    .catch(e => {{
-                        console.warn(\"`WebAssembly.instantiateStreaming` failed. Assuming this is \
-                                        because your server does not serve wasm with \
-                                        `application/wasm` MIME type. Falling back to \
-                                        `WebAssembly.instantiate` which is slower. Original \
-                                        error:\\n\", e);
-                        return response
-                            .then(r => r.arrayBuffer())
-                            .then(bytes => WebAssembly.instantiate(bytes, imports));
-                    }});
-            }} else {{
-                result = response
-                    .then(r => r.arrayBuffer())
-                    .then(bytes => WebAssembly.instantiate(bytes, imports));
-            }}
-        }}
-        return result.then(({{instance, module}}) => {{
-            wasm = init.wasm = instance.exports;
-            init.__wbindgen_wasm_instance = instance;
-            init.__wbindgen_wasm_module = module;
-            init.__wbindgen_wasm_memory = __exports.memory;
-            {start}
-        }});
-    }};
-    self.{global_name} = Object.assign(init, __exports);
-}})();",
-                globals = self.globals,
-                module = module_name,
-                global_name = self
-                    .config
-                    .no_modules_global
-                    .as_ref()
-                    .map(|s| &**s)
-                    .unwrap_or("wasm_bindgen"),
-                init_memory = memory,
-                start = if has_start_function {
-                    "wasm.__wbindgen_start();"
-                } else {
-                    ""
-                },
-            )
-        } else if self.config.no_modules {
-            format!(
-                "\
-(function() {{
-    var wasm;
-    const __exports = {{}};
-    {globals}
-    function init(path_or_module) {{
-        let instantiation;
-        const imports = {{ './{module}': __exports }};
-        if (path_or_module instanceof WebAssembly.Module) {{
-            instantiation = WebAssembly.instantiate(path_or_module, imports)
-                .then(instance => {{
-                    return {{ instance, module: path_or_module }}
-                }});
-        }} else {{
-            const data = fetch(path_or_module);
-            if (typeof WebAssembly.instantiateStreaming === 'function') {{
-                instantiation = WebAssembly.instantiateStreaming(data, imports)
-                    .catch(e => {{
-                        console.warn(\"`WebAssembly.instantiateStreaming` failed. Assuming this is \
-                                       because your server does not serve wasm with \
-                                       `application/wasm` MIME type. Falling back to \
-                                       `WebAssembly.instantiate` which is slower. Original \
-                                       error:\\n\", e);
-                        return data
-                            .then(r => r.arrayBuffer())
-                            .then(bytes => WebAssembly.instantiate(bytes, imports));
-                    }});
-            }} else {{
-                instantiation = data
-                    .then(response => response.arrayBuffer())
-                    .then(buffer => WebAssembly.instantiate(buffer, imports));
-            }}
-        }}
-        return instantiation.then(({{instance}}) => {{
-            wasm = init.wasm = instance.exports;
-            {start}
-        }});
-    }};
-    self.{global_name} = Object.assign(init, __exports);
-}})();",
-                globals = self.globals,
-                module = module_name,
-                global_name = self
-                    .config
-                    .no_modules_global
-                    .as_ref()
-                    .map(|s| &**s)
-                    .unwrap_or("wasm_bindgen"),
-                start = if has_start_function {
-                    "wasm.__wbindgen_start();"
-                } else {
-                    ""
-                },
+            self.imports_post.push_str("let memory;\n");
+            (
+                format!("memory = __exports.memory = maybe_memory;"),
+                format!("memory = __exports.memory = {};", memory),
             )
         } else {
-            let import_wasm = if self.globals.len() == 0 {
-                String::new()
-            } else if self.use_node_require() {
-                self.footer
-                    .push_str(&format!("wasm = require('./{}_bg');", module_name));
-                format!("var wasm;")
-            } else {
-                format!("import * as wasm from './{}_bg';", module_name)
-            };
-
-            format!(
-                "\
-                /* tslint:disable */\n\
-                {import_wasm}\n\
-                {imports}\n\
-                {imports_post}\n\
-
-                {globals}\n\
-                {footer}",
-                import_wasm = import_wasm,
-                globals = self.globals,
-                imports = self.imports,
-                imports_post = self.imports_post,
-                footer = self.footer,
-            )
+            (String::new(), String::new())
         };
 
-        while js.contains("\n\n\n") {
-            js = js.replace("\n\n\n", "\n\n");
-        }
-
-        Ok((js, self.typescript.clone()))
+        format!(
+            "\
+                function init(module_or_path, maybe_memory) {{
+                    let result;
+                    const imports = {{ './{module}': __exports }};
+                    if (module_or_path instanceof WebAssembly.Module) {{
+                        {init_memory1}
+                        result = WebAssembly.instantiate(module_or_path, imports)
+                            .then(instance => {{
+                                return {{ instance, module: module_or_path }};
+                            }});
+                    }} else {{
+                        {init_memory2}
+                        const response = fetch(module_or_path);
+                        if (typeof WebAssembly.instantiateStreaming === 'function') {{
+                            result = WebAssembly.instantiateStreaming(response, imports)
+                                .catch(e => {{
+                                    console.warn(\"`WebAssembly.instantiateStreaming` failed. Assuming this is \
+                                                    because your server does not serve wasm with \
+                                                    `application/wasm` MIME type. Falling back to \
+                                                    `WebAssembly.instantiate` which is slower. Original \
+                                                    error:\\n\", e);
+                                    return response
+                                        .then(r => r.arrayBuffer())
+                                        .then(bytes => WebAssembly.instantiate(bytes, imports));
+                                }});
+                        }} else {{
+                            result = response
+                                .then(r => r.arrayBuffer())
+                                .then(bytes => WebAssembly.instantiate(bytes, imports));
+                        }}
+                    }}
+                    return result.then(({{instance, module}}) => {{
+                        wasm = instance.exports;
+                        init.__wbindgen_wasm_module = module;
+                        {start}
+                        return wasm;
+                    }});
+                }}
+            ",
+            module = module_name,
+            init_memory1 = init_memory1,
+            init_memory2 = init_memory2,
+            start = if needs_manual_start {
+                "wasm.__wbindgen_start();"
+            } else {
+                ""
+            },
+        )
     }
 
     fn bind(
@@ -1235,8 +1310,7 @@ impl<'a> Context<'a> {
                             passStringToWasm = function(arg) {{ {} }};
                         }}
                     ",
-                    use_encode_into,
-                    use_encode,
+                    use_encode_into, use_encode,
                 ));
             }
             _ => {
@@ -1364,14 +1438,14 @@ impl<'a> Context<'a> {
     }
 
     fn expose_text_processor(&mut self, s: &str) {
-        if self.config.nodejs_experimental_modules {
+        if self.config.mode.nodejs_experimental_modules() {
             self.imports
                 .push_str(&format!("import {{ {} }} from 'util';\n", s));
             self.global(&format!("let cached{0} = new {0}('utf-8');", s));
-        } else if self.config.nodejs {
+        } else if self.config.mode.nodejs() {
             self.global(&format!("const {0} = require('util').{0};", s));
             self.global(&format!("let cached{0} = new {0}('utf-8');", s));
-        } else if !(self.config.browser || self.config.no_modules) {
+        } else if !self.config.mode.always_run_in_browser() {
             self.global(&format!(
                 "
                     const l{0} = typeof {0} === 'undefined' ? \
@@ -2008,7 +2082,7 @@ impl<'a> Context<'a> {
     }
 
     fn use_node_require(&self) -> bool {
-        self.config.nodejs && !self.config.nodejs_experimental_modules
+        self.config.mode.nodejs() && !self.config.mode.nodejs_experimental_modules()
     }
 
     fn memory(&mut self) -> &'static str {
@@ -2052,23 +2126,41 @@ impl<'a> Context<'a> {
             .or_insert_with(|| {
                 let name = generate_identifier(import.name(), imported_identifiers);
                 match &import {
-                    Import::Module { module, .. } => {
+                    Import::Module { .. }
+                    | Import::LocalModule { .. }
+                    | Import::InlineJs { .. } => {
+                        // When doing a modular import local snippets (either
+                        // inline or not) are routed to a local `./snippets`
+                        // directory which the rest of `wasm-bindgen` will fill
+                        // in.
+                        let path = match import {
+                            Import::Module { module, .. } => module.to_string(),
+                            Import::LocalModule { module, .. } => format!("./snippets/{}", module),
+                            Import::InlineJs {
+                                unique_crate_identifier,
+                                snippet_idx_in_crate,
+                                ..
+                            } => format!(
+                                "./snippets/{}/inline{}.js",
+                                unique_crate_identifier, snippet_idx_in_crate
+                            ),
+                            _ => unreachable!(),
+                        };
                         if use_node_require {
                             imports.push_str(&format!(
                                 "const {} = require(String.raw`{}`).{};\n",
                                 name,
-                                module,
+                                path,
                                 import.name()
                             ));
                         } else if import.name() == name {
-                            imports
-                                .push_str(&format!("import {{ {} }} from '{}';\n", name, module));
+                            imports.push_str(&format!("import {{ {} }} from '{}';\n", name, path));
                         } else {
                             imports.push_str(&format!(
                                 "import {{ {} as {} }} from '{}';\n",
                                 import.name(),
                                 name,
-                                module
+                                path
                             ));
                         }
                         name
@@ -2290,24 +2382,6 @@ impl<'a> Context<'a> {
         true
     }
 
-    /// Injects a `start` function into the wasm module. This start function
-    /// calls a shim in the generated JS which defers the actual start function
-    /// to the next microtask tick of the event queue.
-    ///
-    /// See docs above at callsite for why this happens.
-    fn inject_start_shim(&mut self) {
-        let body = "function() {
-            Promise.resolve().then(() => wasm.__wbindgen_start());
-        }";
-        self.export("__wbindgen_defer_start", body, None);
-        let ty = self.module.types.add(&[], &[]);
-        let id =
-            self.module
-                .add_import_func("__wbindgen_placeholder__", "__wbindgen_defer_start", ty);
-        assert!(self.module.start.is_none());
-        self.module.start = Some(id);
-    }
-
     fn expose_anyref_table(&mut self) {
         assert!(self.config.anyref);
         if !self.should_write_global("anyref_table") {
@@ -2368,6 +2442,14 @@ impl<'a> Context<'a> {
 
 impl<'a, 'b> SubContext<'a, 'b> {
     pub fn generate(&mut self) -> Result<(), Error> {
+        for m in self.program.local_modules.iter() {
+            // All local modules we find should be unique, but the same module
+            // may have showed up in a few different blocks. If that's the case
+            // all the same identifiers should have the same contents.
+            if let Some(prev) = self.cx.local_modules.insert(m.identifier, m.contents) {
+                assert_eq!(prev, m.contents);
+            }
+        }
         for f in self.program.exports.iter() {
             self.generate_export(f).with_context(|_| {
                 format!(
@@ -2752,16 +2834,44 @@ impl<'a, 'b> SubContext<'a, 'b> {
     ) -> Result<Import<'b>, Error> {
         // First up, imports don't work at all in `--no-modules` mode as we're
         // not sure how to import them.
-        if self.cx.config.no_modules {
-            if let Some(module) = &import.module {
+        let is_local_snippet = match import.module {
+            decode::ImportModule::Named(s) => self.cx.local_modules.contains_key(s),
+            decode::ImportModule::Inline(_) => true,
+            decode::ImportModule::None => false,
+        };
+        if self.cx.config.mode.no_modules() {
+            if is_local_snippet {
+                bail!(
+                    "local JS snippets are not supported with `--no-modules`; \
+                     use `--browser` or no flag instead",
+                );
+            }
+            if let decode::ImportModule::Named(module) = &import.module {
                 bail!(
                     "import from `{}` module not allowed with `--no-modules`; \
-                     use `--nodejs` or `--browser` instead",
+                     use `--nodejs`, `--browser`, or no flag instead",
                     module
                 );
             }
         }
 
+        // FIXME: currently we require that local JS snippets are written in ES
+        // module syntax for imports/exports, but nodejs uses CommonJS to handle
+        // this meaning that local JS snippets are basically guaranteed to be
+        // incompatible. We need to implement a pass that translates the ES
+        // module syntax in the snippet to a CommonJS module, which is in theory
+        // not that hard but is a chunk of work to do.
+        if is_local_snippet && self.cx.config.mode.nodejs() {
+            // have a small unergonomic escape hatch for our webidl-tests tests
+            if env::var("WBINDGEN_I_PROMISE_JS_SYNTAX_WORKS_IN_NODE").is_err() {
+                bail!(
+                    "local JS snippets are not supported with `--nodejs`; \
+                     see rustwasm/rfcs#6 for more details, but this restriction \
+                     will be lifted in the future"
+                );
+            }
+        }
+
         // Similar to `--no-modules`, only allow vendor prefixes basically for web
         // apis, shouldn't be necessary for things like npm packages or other
         // imported items.
@@ -2769,7 +2879,15 @@ impl<'a, 'b> SubContext<'a, 'b> {
         if let Some(vendor_prefixes) = vendor_prefixes {
             assert!(vendor_prefixes.len() > 0);
 
-            if let Some(module) = &import.module {
+            if is_local_snippet {
+                bail!(
+                    "local JS snippets do not support vendor prefixes for \
+                     the import of `{}` with a polyfill of `{}`",
+                    item,
+                    &vendor_prefixes[0]
+                );
+            }
+            if let decode::ImportModule::Named(module) = &import.module {
                 bail!(
                     "import of `{}` from `{}` has a polyfill of `{}` listed, but
                      vendor prefixes aren't supported when importing from modules",
@@ -2792,20 +2910,36 @@ impl<'a, 'b> SubContext<'a, 'b> {
             });
         }
 
-        let name = import.js_namespace.as_ref().map(|s| &**s).unwrap_or(item);
-        let field = if import.js_namespace.is_some() {
-            Some(item)
-        } else {
-            None
+        let (name, field) = match import.js_namespace {
+            Some(ns) => (ns, Some(item)),
+            None => (item, None),
         };
 
         Ok(match import.module {
-            Some(module) => Import::Module {
+            decode::ImportModule::Named(module) if is_local_snippet => Import::LocalModule {
                 module,
                 name,
                 field,
             },
-            None => Import::Global { name, field },
+            decode::ImportModule::Named(module) => Import::Module {
+                module,
+                name,
+                field,
+            },
+            decode::ImportModule::Inline(idx) => {
+                let offset = *self
+                    .cx
+                    .snippet_offsets
+                    .get(self.program.unique_crate_identifier)
+                    .unwrap_or(&0);
+                Import::InlineJs {
+                    unique_crate_identifier: self.program.unique_crate_identifier,
+                    snippet_idx_in_crate: idx as usize + offset,
+                    name,
+                    field,
+                }
+            }
+            decode::ImportModule::None => Import::Global { name, field },
         })
     }
 
@@ -2815,17 +2949,34 @@ impl<'a, 'b> SubContext<'a, 'b> {
     }
 }
 
+#[derive(Hash, Eq, PartialEq)]
+pub enum ImportModule<'a> {
+    Named(&'a str),
+    Inline(&'a str, usize),
+    None,
+}
+
 impl<'a> Import<'a> {
-    fn module(&self) -> Option<&'a str> {
+    fn module(&self) -> ImportModule<'a> {
         match self {
-            Import::Module { module, .. } => Some(module),
-            _ => None,
+            Import::Module { module, .. } | Import::LocalModule { module, .. } => {
+                ImportModule::Named(module)
+            }
+            Import::InlineJs {
+                unique_crate_identifier,
+                snippet_idx_in_crate,
+                ..
+            } => ImportModule::Inline(unique_crate_identifier, *snippet_idx_in_crate),
+            Import::Global { .. } | Import::VendorPrefixed { .. } => ImportModule::None,
         }
     }
 
     fn field(&self) -> Option<&'a str> {
         match self {
-            Import::Module { field, .. } | Import::Global { field, .. } => *field,
+            Import::Module { field, .. }
+            | Import::LocalModule { field, .. }
+            | Import::InlineJs { field, .. }
+            | Import::Global { field, .. } => *field,
             Import::VendorPrefixed { .. } => None,
         }
     }
@@ -2833,6 +2984,8 @@ impl<'a> Import<'a> {
     fn name(&self) -> &'a str {
         match self {
             Import::Module { name, .. }
+            | Import::LocalModule { name, .. }
+            | Import::InlineJs { name, .. }
             | Import::Global { name, .. }
             | Import::VendorPrefixed { name, .. } => *name,
         }

crates/cli-support/src/lib.rs

@@ -17,11 +17,7 @@ pub mod wasm2es6js;
 pub struct Bindgen {
     input: Input,
     out_name: Option<String>,
-    nodejs: bool,
-    nodejs_experimental_modules: bool,
-    browser: bool,
-    no_modules: bool,
-    no_modules_global: Option<String>,
+    mode: OutputMode,
     debug: bool,
     typescript: bool,
     demangle: bool,
@@ -39,6 +35,13 @@ pub struct Bindgen {
     encode_into: EncodeInto,
 }
 
+enum OutputMode {
+    Bundler,
+    Browser,
+    NoModules { global: String },
+    Node { experimental_modules: bool },
+}
+
 enum Input {
     Path(PathBuf),
     Module(Module, String),
@@ -56,11 +59,7 @@ impl Bindgen {
         Bindgen {
             input: Input::None,
             out_name: None,
-            nodejs: false,
-            nodejs_experimental_modules: false,
-            browser: false,
-            no_modules: false,
-            no_modules_global: None,
+            mode: OutputMode::Bundler,
             debug: false,
             typescript: false,
             demangle: true,
@@ -92,29 +91,66 @@ impl Bindgen {
         return self;
     }
 
-    pub fn nodejs(&mut self, node: bool) -> &mut Bindgen {
-        self.nodejs = node;
-        self
+    fn switch_mode(&mut self, mode: OutputMode, flag: &str) -> Result<(), Error> {
+        match self.mode {
+            OutputMode::Bundler => self.mode = mode,
+            _ => bail!(
+                "cannot specify `{}` with another output mode already specified",
+                flag
+            ),
+        }
+        Ok(())
     }
 
-    pub fn nodejs_experimental_modules(&mut self, node: bool) -> &mut Bindgen {
-        self.nodejs_experimental_modules = node;
-        self
+    pub fn nodejs(&mut self, node: bool) -> Result<&mut Bindgen, Error> {
+        if node {
+            self.switch_mode(
+                OutputMode::Node {
+                    experimental_modules: false,
+                },
+                "--nodejs",
+            )?;
+        }
+        Ok(self)
     }
 
-    pub fn browser(&mut self, browser: bool) -> &mut Bindgen {
-        self.browser = browser;
-        self
+    pub fn nodejs_experimental_modules(&mut self, node: bool) -> Result<&mut Bindgen, Error> {
+        if node {
+            self.switch_mode(
+                OutputMode::Node {
+                    experimental_modules: true,
+                },
+                "--nodejs-experimental-modules",
+            )?;
+        }
+        Ok(self)
     }
 
-    pub fn no_modules(&mut self, no_modules: bool) -> &mut Bindgen {
-        self.no_modules = no_modules;
-        self
+    pub fn browser(&mut self, browser: bool) -> Result<&mut Bindgen, Error> {
+        if browser {
+            self.switch_mode(OutputMode::Browser, "--browser")?;
+        }
+        Ok(self)
     }
 
-    pub fn no_modules_global(&mut self, name: &str) -> &mut Bindgen {
-        self.no_modules_global = Some(name.to_string());
-        self
+    pub fn no_modules(&mut self, no_modules: bool) -> Result<&mut Bindgen, Error> {
+        if no_modules {
+            self.switch_mode(
+                OutputMode::NoModules {
+                    global: "wasm_bindgen".to_string(),
+                },
+                "--no-modules",
+            )?;
+        }
+        Ok(self)
+    }
+
+    pub fn no_modules_global(&mut self, name: &str) -> Result<&mut Bindgen, Error> {
+        match &mut self.mode {
+            OutputMode::NoModules { global } => *global = name.to_string(),
+            _ => bail!("can only specify `--no-modules-global` with `--no-modules`"),
+        }
+        Ok(self)
     }
 
     pub fn debug(&mut self, debug: bool) -> &mut Bindgen {
@@ -203,8 +239,10 @@ impl Bindgen {
         // a module's start function, if any, because we assume start functions
         // only show up when injected on behalf of wasm-bindgen's passes.
         if module.start.is_some() {
-            bail!("wasm-bindgen is currently incompatible with modules that \
-                   already have a start function");
+            bail!(
+                "wasm-bindgen is currently incompatible with modules that \
+                 already have a start function"
+            );
         }
 
         let mut program_storage = Vec::new();
@@ -263,8 +301,10 @@ impl Bindgen {
                 imported_functions: Default::default(),
                 imported_statics: Default::default(),
                 direct_imports: Default::default(),
+                local_modules: Default::default(),
                 start: None,
                 anyref: Default::default(),
+                snippet_offsets: Default::default(),
             };
             cx.anyref.enabled = self.anyref;
             cx.anyref.prepare(cx.module)?;
@@ -275,11 +315,37 @@ impl Bindgen {
                     vendor_prefixes: Default::default(),
                 }
                 .generate()?;
+
+                let offset = cx
+                    .snippet_offsets
+                    .entry(program.unique_crate_identifier)
+                    .or_insert(0);
+                for js in program.inline_js.iter() {
+                    let name = format!("inline{}.js", *offset);
+                    *offset += 1;
+                    let path = out_dir
+                        .join("snippets")
+                        .join(program.unique_crate_identifier)
+                        .join(name);
+                    fs::create_dir_all(path.parent().unwrap())?;
+                    fs::write(&path, js)
+                        .with_context(|_| format!("failed to write `{}`", path.display()))?;
+                }
             }
+
+            // Write out all local JS snippets to the final destination now that
+            // we've collected them from all the programs.
+            for (path, contents) in cx.local_modules.iter() {
+                let path = out_dir.join("snippets").join(path);
+                fs::create_dir_all(path.parent().unwrap())?;
+                fs::write(&path, contents)
+                    .with_context(|_| format!("failed to write `{}`", path.display()))?;
+            }
+
             cx.finalize(stem)?
         };
 
-        let extension = if self.nodejs_experimental_modules {
+        let extension = if self.mode.nodejs_experimental_modules() {
             "mjs"
         } else {
             "js"
@@ -296,7 +362,7 @@ impl Bindgen {
 
         let wasm_path = out_dir.join(format!("{}_bg", stem)).with_extension("wasm");
 
-        if self.nodejs {
+        if self.mode.nodejs() {
             let js_path = wasm_path.with_extension(extension);
             let shim = self.generate_node_wasm_import(&module, &wasm_path);
             fs::write(&js_path, shim)
@@ -325,7 +391,7 @@ impl Bindgen {
 
         let mut shim = String::new();
 
-        if self.nodejs_experimental_modules {
+        if self.mode.nodejs_experimental_modules() {
             for (i, module) in imports.iter().enumerate() {
                 shim.push_str(&format!("import * as import{} from '{}';\n", i, module));
             }
@@ -357,7 +423,7 @@ impl Bindgen {
         }
         shim.push_str("let imports = {};\n");
         for (i, module) in imports.iter().enumerate() {
-            if self.nodejs_experimental_modules {
+            if self.mode.nodejs_experimental_modules() {
                 shim.push_str(&format!("imports['{}'] = import{};\n", module, i));
             } else {
                 shim.push_str(&format!("imports['{0}'] = require('{0}');\n", module));
@@ -371,7 +437,7 @@ impl Bindgen {
             ",
         ));
 
-        if self.nodejs_experimental_modules {
+        if self.mode.nodejs_experimental_modules() {
             for entry in m.exports.iter() {
                 shim.push_str("export const ");
                 shim.push_str(&entry.name);
@@ -567,3 +633,43 @@ fn demangle(module: &mut Module) {
         }
     }
 }
+
+impl OutputMode {
+    fn nodejs_experimental_modules(&self) -> bool {
+        match self {
+            OutputMode::Node {
+                experimental_modules,
+            } => *experimental_modules,
+            _ => false,
+        }
+    }
+
+    fn nodejs(&self) -> bool {
+        match self {
+            OutputMode::Node { .. } => true,
+            _ => false,
+        }
+    }
+
+    fn no_modules(&self) -> bool {
+        match self {
+            OutputMode::NoModules { .. } => true,
+            _ => false,
+        }
+    }
+
+    fn always_run_in_browser(&self) -> bool {
+        match self {
+            OutputMode::Browser => true,
+            OutputMode::NoModules { .. } => true,
+            _ => false,
+        }
+    }
+
+    fn browser(&self) -> bool {
+        match self {
+            OutputMode::Browser => true,
+            _ => false,
+        }
+    }
+}

crates/cli/src/bin/wasm-bindgen-test-runner/headless.rs

@@ -506,6 +506,7 @@ impl<'a> BackgroundChild<'a> {
         cmd.stdout(Stdio::piped())
             .stderr(Stdio::piped())
             .stdin(Stdio::null());
+        log::debug!("executing {:?}", cmd);
         let mut child = cmd
             .spawn()
             .context(format!("failed to spawn {:?} binary", path))?;

crates/cli/src/bin/wasm-bindgen-test-runner/main.rs

@@ -107,7 +107,8 @@ fn rmain() -> Result<(), Error> {
     shell.status("Executing bindgen...");
     let mut b = Bindgen::new();
     b.debug(debug)
-        .nodejs(node)
+        .nodejs(node)?
+        .browser(!node)?
         .input_module(module, wasm)
         .keep_debug(false)
         .emit_start(false)

crates/cli/src/bin/wasm-bindgen-test-runner/server.rs

@@ -5,7 +5,6 @@ use std::path::Path;
 
 use failure::{format_err, Error, ResultExt};
 use rouille::{Request, Response, Server};
-use wasm_bindgen_cli_support::wasm2es6js::Config;
 
 pub fn spawn(
     addr: &SocketAddr,
@@ -23,9 +22,9 @@ pub fn spawn(
             __wbgtest_console_log,
             __wbgtest_console_info,
             __wbgtest_console_warn,
-            __wbgtest_console_error
+            __wbgtest_console_error,
+            default as init,
         }} from './{0}';
-        import * as wasm from './{0}_bg';
 
         // Now that we've gotten to the point where JS is executing, update our
         // status text as at this point we should be asynchronously fetching the
@@ -33,9 +32,7 @@ pub fn spawn(
         document.getElementById('output').textContent = "Loading wasm module...";
 
         async function main(test) {{
-            // this is a facet of using wasm2es6js, a hack until browsers have
-            // native ESM support for wasm modules.
-            await wasm.booted;
+            const wasm = await init('./{0}_bg.wasm');
 
             const cx = new Context();
             window.on_console_debug = __wbgtest_console_debug;
@@ -65,25 +62,6 @@ pub fn spawn(
     let js_path = tmpdir.join("run.js");
     fs::write(&js_path, js_to_execute).context("failed to write JS file")?;
 
-    // No browser today supports a wasm file as ES modules natively, so we need
-    // to shim it. Use `wasm2es6js` here to fetch an appropriate URL and look
-    // like an ES module with the wasm module under the hood.
-    //
-    // TODO: don't reparse the wasm module here, should pass the
-    //       `Module struct` directly from the output of
-    //       `wasm-bindgen` previously here and avoid unnecessary
-    //       parsing.
-    let wasm_name = format!("{}_bg.wasm", module);
-    let wasm = fs::read(tmpdir.join(&wasm_name))?;
-    let output = Config::new()
-        .fetch(Some(format!("/{}", wasm_name)))
-        .generate(&wasm)?;
-    let (js, wasm) = output.js_and_wasm()?;
-    let wasm = wasm.unwrap();
-    fs::write(tmpdir.join(format!("{}_bg.js", module)), js).context("failed to write JS file")?;
-    fs::write(tmpdir.join(format!("{}_bg.wasm", module)), wasm)
-        .context("failed to write wasm file")?;
-
     // For now, always run forever on this port. We may update this later!
     let tmpdir = tmpdir.to_path_buf();
     let srv = Server::new(addr, move |request| {

crates/cli/src/bin/wasm-bindgen.rs

@@ -88,9 +88,9 @@ fn rmain(args: &Args) -> Result<(), Error> {
 
     let mut b = Bindgen::new();
     b.input_path(input)
-        .nodejs(args.flag_nodejs)
-        .browser(args.flag_browser)
-        .no_modules(args.flag_no_modules)
+        .nodejs(args.flag_nodejs)?
+        .browser(args.flag_browser)?
+        .no_modules(args.flag_no_modules)?
         .debug(args.flag_debug)
         .demangle(!args.flag_no_demangle)
         .keep_debug(args.flag_keep_debug)
@@ -98,7 +98,7 @@ fn rmain(args: &Args) -> Result<(), Error> {
         .remove_producers_section(args.flag_remove_producers_section)
         .typescript(typescript);
     if let Some(ref name) = args.flag_no_modules_global {
-        b.no_modules_global(name);
+        b.no_modules_global(name)?;
     }
     if let Some(ref name) = args.flag_out_name {
         b.out_name(name);

crates/js-sys/tests/headless.rs

@@ -10,7 +10,7 @@ use wasm_bindgen_test::*;
 
 wasm_bindgen_test_configure!(run_in_browser);
 
-#[wasm_bindgen(module = "./tests/headless.js")]
+#[wasm_bindgen(module = "/tests/headless.js")]
 extern "C" {
     fn is_array_values_supported() -> bool;
 }

crates/macro-support/Cargo.toml

@@ -9,6 +9,7 @@ documentation = "https://docs.rs/wasm-bindgen"
 description = """
 The part of the implementation of the `#[wasm_bindgen]` attribute that is not in the shared backend crate
 """
+edition = '2018'
 
 [features]
 spans = ["wasm-bindgen-backend/spans"]

crates/macro-support/src/lib.rs

@@ -12,8 +12,8 @@ extern crate wasm_bindgen_backend as backend;
 extern crate wasm_bindgen_shared as shared;
 
 use backend::{Diagnostic, TryToTokens};
-pub use parser::BindgenAttrs;
-use parser::MacroParse;
+pub use crate::parser::BindgenAttrs;
+use crate::parser::MacroParse;
 use proc_macro2::TokenStream;
 use quote::ToTokens;
 use quote::TokenStreamExt;

crates/macro-support/src/parser.rs

@@ -33,6 +33,7 @@ macro_rules! attrgen {
             (static_method_of, StaticMethodOf(Span, Ident)),
             (js_namespace, JsNamespace(Span, Ident)),
             (module, Module(Span, String, Span)),
+            (inline_js, InlineJs(Span, String, Span)),
             (getter, Getter(Span, Option<Ident>)),
             (setter, Setter(Span, Option<Ident>)),
             (indexing_getter, IndexingGetter(Span)),
@@ -339,12 +340,12 @@ impl<'a> ConvertToAst<BindgenAttrs> for &'a mut syn::ItemStruct {
     }
 }
 
-impl<'a> ConvertToAst<(BindgenAttrs, &'a Option<String>)> for syn::ForeignItemFn {
+impl<'a> ConvertToAst<(BindgenAttrs, &'a ast::ImportModule)> for syn::ForeignItemFn {
     type Target = ast::ImportKind;
 
     fn convert(
         self,
-        (opts, module): (BindgenAttrs, &'a Option<String>),
+        (opts, module): (BindgenAttrs, &'a ast::ImportModule),
     ) -> Result<Self::Target, Diagnostic> {
         let wasm = function_from_decl(
             &self.ident,
@@ -543,12 +544,12 @@ impl ConvertToAst<BindgenAttrs> for syn::ForeignItemType {
     }
 }
 
-impl<'a> ConvertToAst<(BindgenAttrs, &'a Option<String>)> for syn::ForeignItemStatic {
+impl<'a> ConvertToAst<(BindgenAttrs, &'a ast::ImportModule)> for syn::ForeignItemStatic {
     type Target = ast::ImportKind;
 
     fn convert(
         self,
-        (opts, module): (BindgenAttrs, &'a Option<String>),
+        (opts, module): (BindgenAttrs, &'a ast::ImportModule),
     ) -> Result<Self::Target, Diagnostic> {
         if self.mutability.is_some() {
             bail_span!(self.mutability, "cannot import mutable globals yet")
@@ -1084,8 +1085,27 @@ impl MacroParse<BindgenAttrs> for syn::ItemForeignMod {
                 ));
             }
         }
-        for mut item in self.items.into_iter() {
-            if let Err(e) = item.macro_parse(program, &opts) {
+        let module = match opts.module() {
+            Some((name, span)) => {
+                if opts.inline_js().is_some() {
+                    let msg = "cannot specify both `module` and `inline_js`";
+                    errors.push(Diagnostic::span_error(span, msg));
+                }
+                ast::ImportModule::Named(name.to_string(), span)
+            }
+            None => {
+                match opts.inline_js() {
+                    Some((js, span)) => {
+                        let i = program.inline_js.len();
+                        program.inline_js.push(js.to_string());
+                        ast::ImportModule::Inline(i, span)
+                    }
+                    None => ast::ImportModule::None
+                }
+            }
+        };
+        for item in self.items.into_iter() {
+            if let Err(e) = item.macro_parse(program, module.clone()) {
                 errors.push(e);
             }
         }
@@ -1095,11 +1115,11 @@ impl MacroParse<BindgenAttrs> for syn::ItemForeignMod {
     }
 }
 
-impl<'a> MacroParse<&'a BindgenAttrs> for syn::ForeignItem {
+impl MacroParse<ast::ImportModule> for syn::ForeignItem {
     fn macro_parse(
         mut self,
         program: &mut ast::Program,
-        opts: &'a BindgenAttrs,
+        module: ast::ImportModule,
     ) -> Result<(), Diagnostic> {
         let item_opts = {
             let attrs = match self {
@@ -1110,11 +1130,7 @@ impl<'a> MacroParse<&'a BindgenAttrs> for syn::ForeignItem {
             };
             BindgenAttrs::find(attrs)?
         };
-        let module = item_opts
-            .module()
-            .or(opts.module())
-            .map(|s| s.0.to_string());
-        let js_namespace = item_opts.js_namespace().or(opts.js_namespace()).cloned();
+        let js_namespace = item_opts.js_namespace().cloned();
         let kind = match self {
             syn::ForeignItem::Fn(f) => f.convert((item_opts, &module))?,
             syn::ForeignItem::Type(t) => t.convert(item_opts)?,

crates/macro/ui-tests/import-local.rs

@@ -0,0 +1,15 @@
+extern crate wasm_bindgen;
+
+use wasm_bindgen::prelude::*;
+
+#[wasm_bindgen(module = "./foo.js")]
+extern {
+    fn wut();
+}
+
+#[wasm_bindgen(module = "../foo.js")]
+extern {
+    fn wut();
+}
+
+fn main() {}

crates/macro/ui-tests/import-local.stderr

@@ -0,0 +1,14 @@
+error: relative module paths aren't supported yet
+ --> $DIR/import-local.rs:5:25
+  |
+5 | #[wasm_bindgen(module = "./foo.js")]
+  |                         ^^^^^^^^^^
+
+error: relative module paths aren't supported yet
+  --> $DIR/import-local.rs:10:25
+   |
+10 | #[wasm_bindgen(module = "../foo.js")]
+   |                         ^^^^^^^^^^^
+
+error: aborting due to 2 previous errors
+

crates/shared/src/lib.rs

@@ -14,16 +14,23 @@ macro_rules! shared_api {
             imports: Vec<Import<'a>>,
             structs: Vec<Struct<'a>>,
             typescript_custom_sections: Vec<&'a str>,
-            // version: &'a str,
-            // schema_version: &'a str,
+            local_modules: Vec<LocalModule<'a>>,
+            inline_js: Vec<&'a str>,
+            unique_crate_identifier: &'a str,
         }
 
         struct Import<'a> {
-            module: Option<&'a str>,
+            module: ImportModule<'a>,
             js_namespace: Option<&'a str>,
             kind: ImportKind<'a>,
         }
 
+        enum ImportModule<'a> {
+            None,
+            Named(&'a str),
+            Inline(u32),
+        }
+
         enum ImportKind<'a> {
             Function(ImportFunction<'a>),
             Static(ImportStatic<'a>),
@@ -113,6 +120,11 @@ macro_rules! shared_api {
             readonly: bool,
             comments: Vec<&'a str>,
         }
+
+        struct LocalModule<'a> {
+            identifier: &'a str,
+            contents: &'a str,
+        }
         }
     }; // end of mac case
 } // end of mac definition

crates/web-sys/tests/wasm/anchor_element.rs

@@ -2,7 +2,7 @@ use wasm_bindgen::prelude::*;
 use wasm_bindgen_test::*;
 use web_sys::HtmlAnchorElement;
 
-#[wasm_bindgen(module = "./tests/wasm/element.js")]
+#[wasm_bindgen(module = "/tests/wasm/element.js")]
 extern "C" {
     fn new_a() -> HtmlAnchorElement;
 }

crates/web-sys/tests/wasm/body_element.rs

@@ -2,7 +2,7 @@ use wasm_bindgen::prelude::*;
 use wasm_bindgen_test::*;
 use web_sys::HtmlBodyElement;
 
-#[wasm_bindgen(module = "./tests/wasm/element.js")]
+#[wasm_bindgen(module = "/tests/wasm/element.js")]
 extern "C" {
     fn new_body() -> HtmlBodyElement;
 }

crates/web-sys/tests/wasm/br_element.rs

@@ -2,7 +2,7 @@ use wasm_bindgen::prelude::*;
 use wasm_bindgen_test::*;
 use web_sys::HtmlBrElement;
 
-#[wasm_bindgen(module = "./tests/wasm/element.js")]
+#[wasm_bindgen(module = "/tests/wasm/element.js")]
 extern "C" {
     fn new_br() -> HtmlBrElement;
 }

crates/web-sys/tests/wasm/button_element.rs

@@ -2,7 +2,7 @@ use wasm_bindgen::prelude::*;
 use wasm_bindgen_test::*;
 use web_sys::{HtmlButtonElement, HtmlFormElement, Node};
 
-#[wasm_bindgen(module = "./tests/wasm/element.js")]
+#[wasm_bindgen(module = "/tests/wasm/element.js")]
 extern "C" {
     fn new_button() -> HtmlButtonElement;
     fn new_form() -> HtmlFormElement;

crates/web-sys/tests/wasm/div_element.rs

@@ -2,7 +2,7 @@ use wasm_bindgen::prelude::*;
 use wasm_bindgen_test::*;
 use web_sys::HtmlDivElement;
 
-#[wasm_bindgen(module = "./tests/wasm/element.js")]
+#[wasm_bindgen(module = "/tests/wasm/element.js")]
 extern "C" {
     fn new_div() -> HtmlDivElement;
 }

crates/web-sys/tests/wasm/element.rs

@@ -2,7 +2,7 @@ use wasm_bindgen::prelude::*;
 use wasm_bindgen_test::*;
 use web_sys::Element;
 
-#[wasm_bindgen(module = "./tests/wasm/element.js")]
+#[wasm_bindgen(module = "/tests/wasm/element.js")]
 extern "C" {
     fn new_div() -> Element;
 }

crates/web-sys/tests/wasm/event.rs

@@ -6,7 +6,7 @@ use wasm_bindgen_futures::JsFuture;
 use wasm_bindgen_test::*;
 use web_sys::Event;
 
-#[wasm_bindgen(module = "./tests/wasm/event.js")]
+#[wasm_bindgen(module = "/tests/wasm/event.js")]
 extern "C" {
     fn new_event() -> Promise;
 }

crates/web-sys/tests/wasm/head_element.rs

@@ -2,7 +2,7 @@ use wasm_bindgen::prelude::*;
 use wasm_bindgen_test::*;
 use web_sys::HtmlHeadElement;
 
-#[wasm_bindgen(module = "./tests/wasm/element.js")]
+#[wasm_bindgen(module = "/tests/wasm/element.js")]
 extern "C" {
     fn new_head() -> HtmlHeadElement;
 }

crates/web-sys/tests/wasm/headers.rs

@@ -2,7 +2,7 @@ use wasm_bindgen::prelude::*;
 use wasm_bindgen_test::*;
 use web_sys::Headers;
 
-#[wasm_bindgen(module = "./tests/wasm/headers.js")]
+#[wasm_bindgen(module = "/tests/wasm/headers.js")]
 extern "C" {
     fn new_headers() -> Headers;
 }

crates/web-sys/tests/wasm/heading_element.rs

@@ -2,7 +2,7 @@ use wasm_bindgen::prelude::*;
 use wasm_bindgen_test::*;
 use web_sys::HtmlHeadingElement;
 
-#[wasm_bindgen(module = "./tests/wasm/element.js")]
+#[wasm_bindgen(module = "/tests/wasm/element.js")]
 extern "C" {
     fn new_heading() -> HtmlHeadingElement;
 }

crates/web-sys/tests/wasm/hr_element.rs

@@ -2,7 +2,7 @@ use wasm_bindgen::prelude::*;
 use wasm_bindgen_test::*;
 use web_sys::HtmlHrElement;
 
-#[wasm_bindgen(module = "./tests/wasm/element.js")]
+#[wasm_bindgen(module = "/tests/wasm/element.js")]
 extern "C" {
     fn new_hr() -> HtmlHrElement;
 }

crates/web-sys/tests/wasm/html_element.rs

@@ -3,7 +3,7 @@ use wasm_bindgen::JsCast;
 use wasm_bindgen_test::*;
 use web_sys::HtmlElement;
 
-#[wasm_bindgen(module = "./tests/wasm/element.js")]
+#[wasm_bindgen(module = "/tests/wasm/element.js")]
 extern "C" {
     fn new_html() -> HtmlElement;
 }

crates/web-sys/tests/wasm/html_html_element.rs

@@ -2,7 +2,7 @@ use wasm_bindgen::prelude::*;
 use wasm_bindgen_test::*;
 use web_sys::HtmlHtmlElement;
 
-#[wasm_bindgen(module = "./tests/wasm/element.js")]
+#[wasm_bindgen(module = "/tests/wasm/element.js")]
 extern "C" {
     fn new_html() -> HtmlHtmlElement;
 }

crates/web-sys/tests/wasm/input_element.rs

@@ -2,7 +2,7 @@ use wasm_bindgen::prelude::*;
 use wasm_bindgen_test::*;
 use web_sys::HtmlInputElement;
 
-#[wasm_bindgen(module = "./tests/wasm/element.js")]
+#[wasm_bindgen(module = "/tests/wasm/element.js")]
 extern "C" {
     fn new_input() -> HtmlInputElement;
 }

crates/web-sys/tests/wasm/menu_element.rs

@@ -2,7 +2,7 @@ use wasm_bindgen_test::*;
 use wasm_bindgen::prelude::*;
 use web_sys::HtmlMenuElement;
 
-#[wasm_bindgen(module = "./tests/wasm/element.js")]
+#[wasm_bindgen(module = "/tests/wasm/element.js")]
 extern "C" {
     fn new_menu() -> HtmlMenuElement;
 }

crates/web-sys/tests/wasm/menu_item_element.rs

@@ -2,7 +2,7 @@ use wasm_bindgen_test::*;
 use wasm_bindgen::prelude::*;
 use web_sys::HtmlMenuItemElement;
 
-#[wasm_bindgen(module = "./tests/wasm/element.js")]
+#[wasm_bindgen(module = "/tests/wasm/element.js")]
 extern "C" {
     fn new_menuitem() -> HtmlMenuItemElement;
 }

crates/web-sys/tests/wasm/meta_element.rs

@@ -2,7 +2,7 @@ use wasm_bindgen::prelude::*;
 use wasm_bindgen_test::*;
 use web_sys::HtmlMetaElement;
 
-#[wasm_bindgen(module = "./tests/wasm/element.js")]
+#[wasm_bindgen(module = "/tests/wasm/element.js")]
 extern "C" {
     fn new_meta() -> HtmlMetaElement;
 }

crates/web-sys/tests/wasm/meter_element.rs

@@ -2,7 +2,7 @@ use wasm_bindgen::prelude::*;
 use wasm_bindgen_test::*;
 use web_sys::HtmlMeterElement;
 
-#[wasm_bindgen(module = "./tests/wasm/element.js")]
+#[wasm_bindgen(module = "/tests/wasm/element.js")]
 extern "C" {
     fn new_meter() -> HtmlMeterElement;
 }

crates/web-sys/tests/wasm/mod_elements.rs

@@ -2,7 +2,7 @@ use wasm_bindgen::prelude::*;
 use wasm_bindgen_test::*;
 use web_sys::HtmlModElement;
 
-#[wasm_bindgen(module = "./tests/wasm/element.js")]
+#[wasm_bindgen(module = "/tests/wasm/element.js")]
 extern "C" {
     fn new_del() -> HtmlModElement;
     fn new_ins() -> HtmlModElement;

crates/web-sys/tests/wasm/olist_element.rs

@@ -2,7 +2,7 @@ use wasm_bindgen::prelude::*;
 use wasm_bindgen_test::*;
 use web_sys::HtmlOListElement;
 
-#[wasm_bindgen(module = "./tests/wasm/element.js")]
+#[wasm_bindgen(module = "/tests/wasm/element.js")]
 extern "C" {
     fn new_olist() -> HtmlOListElement;
 }

crates/web-sys/tests/wasm/optgroup_element.rs

@@ -2,7 +2,7 @@ use wasm_bindgen::prelude::*;
 use wasm_bindgen_test::*;
 use web_sys::HtmlOptGroupElement;
 
-#[wasm_bindgen(module = "./tests/wasm/element.js")]
+#[wasm_bindgen(module = "/tests/wasm/element.js")]
 extern "C" {
     fn new_optgroup() -> HtmlOptGroupElement;
 }

crates/web-sys/tests/wasm/options_collection.rs

@@ -2,7 +2,7 @@ use wasm_bindgen::prelude::*;
 use wasm_bindgen_test::*;
 use web_sys::HtmlOptionsCollection;
 
-#[wasm_bindgen(module = "./tests/wasm/element.js")]
+#[wasm_bindgen(module = "/tests/wasm/element.js")]
 extern "C" {
     fn new_food_options_collection() -> HtmlOptionsCollection;
 }

crates/web-sys/tests/wasm/output_element.rs

@@ -2,7 +2,7 @@ use wasm_bindgen::prelude::*;
 use wasm_bindgen_test::*;
 use web_sys::HtmlOutputElement;
 
-#[wasm_bindgen(module = "./tests/wasm/element.js")]
+#[wasm_bindgen(module = "/tests/wasm/element.js")]
 extern "C" {
     fn new_output() -> HtmlOutputElement;
 }

crates/web-sys/tests/wasm/paragraph_element.rs

@@ -2,7 +2,7 @@ use wasm_bindgen::prelude::*;
 use wasm_bindgen_test::*;
 use web_sys::HtmlParagraphElement;
 
-#[wasm_bindgen(module = "./tests/wasm/element.js")]
+#[wasm_bindgen(module = "/tests/wasm/element.js")]
 extern "C" {
     fn new_paragraph() -> HtmlParagraphElement;
 }

crates/web-sys/tests/wasm/param_element.rs

@@ -2,7 +2,7 @@ use wasm_bindgen::prelude::*;
 use wasm_bindgen_test::*;
 use web_sys::HtmlParamElement;
 
-#[wasm_bindgen(module = "./tests/wasm/element.js")]
+#[wasm_bindgen(module = "/tests/wasm/element.js")]
 extern "C" {
     fn new_param() -> HtmlParamElement;
 }

crates/web-sys/tests/wasm/pre_element.rs

@@ -2,7 +2,7 @@ use wasm_bindgen::prelude::*;
 use wasm_bindgen_test::*;
 use web_sys::HtmlPreElement;
 
-#[wasm_bindgen(module = "./tests/wasm/element.js")]
+#[wasm_bindgen(module = "/tests/wasm/element.js")]
 extern "C" {
     fn new_pre() -> HtmlPreElement;
 }

crates/web-sys/tests/wasm/progress_element.rs

@@ -2,7 +2,7 @@ use wasm_bindgen::prelude::*;
 use wasm_bindgen_test::*;
 use web_sys::HtmlProgressElement;
 
-#[wasm_bindgen(module = "./tests/wasm/element.js")]
+#[wasm_bindgen(module = "/tests/wasm/element.js")]
 extern "C" {
     fn new_progress() -> HtmlProgressElement;
 }

crates/web-sys/tests/wasm/quote_element.rs

@@ -2,7 +2,7 @@ use wasm_bindgen::prelude::*;
 use wasm_bindgen_test::*;
 use web_sys::HtmlQuoteElement;
 
-#[wasm_bindgen(module = "./tests/wasm/element.js")]
+#[wasm_bindgen(module = "/tests/wasm/element.js")]
 extern "C" {
     fn new_quote() -> HtmlQuoteElement;
 }

crates/web-sys/tests/wasm/response.rs

@@ -10,7 +10,7 @@ use wasm_bindgen_futures::JsFuture;
 use wasm_bindgen_test::*;
 use web_sys::Response;
 
-#[wasm_bindgen(module = "./tests/wasm/response.js")]
+#[wasm_bindgen(module = "/tests/wasm/response.js")]
 extern "C" {
     fn new_response() -> Response;
 }

crates/web-sys/tests/wasm/script_element.rs

@@ -2,7 +2,7 @@ use wasm_bindgen::prelude::*;
 use wasm_bindgen_test::*;
 use web_sys::HtmlScriptElement;
 
-#[wasm_bindgen(module = "./tests/wasm/element.js")]
+#[wasm_bindgen(module = "/tests/wasm/element.js")]
 extern "C" {
     fn new_script() -> HtmlScriptElement;
 }

crates/web-sys/tests/wasm/select_element.rs

@@ -2,7 +2,7 @@ use wasm_bindgen::prelude::*;
 use wasm_bindgen_test::*;
 use web_sys::HtmlSelectElement;
 
-#[wasm_bindgen(module = "./tests/wasm/element.js")]
+#[wasm_bindgen(module = "/tests/wasm/element.js")]
 extern "C" {
     fn new_select_with_food_opts() -> HtmlSelectElement;
 }

crates/web-sys/tests/wasm/slot_element.rs

@@ -2,7 +2,7 @@ use wasm_bindgen::prelude::*;
 use wasm_bindgen_test::*;
 use web_sys::HtmlSlotElement;
 
-#[wasm_bindgen(module = "./tests/wasm/element.js")]
+#[wasm_bindgen(module = "/tests/wasm/element.js")]
 extern "C" {
     fn new_slot() -> HtmlSlotElement;
 }

crates/web-sys/tests/wasm/span_element.rs

@@ -2,7 +2,7 @@ use wasm_bindgen::prelude::*;
 use wasm_bindgen_test::*;
 use web_sys::HtmlSpanElement;
 
-#[wasm_bindgen(module = "./tests/wasm/element.js")]
+#[wasm_bindgen(module = "/tests/wasm/element.js")]
 extern "C" {
     fn new_span() -> HtmlSpanElement;
 }

crates/web-sys/tests/wasm/style_element.rs

@@ -2,7 +2,7 @@ use wasm_bindgen::prelude::*;
 use wasm_bindgen_test::*;
 use web_sys::HtmlStyleElement;
 
-#[wasm_bindgen(module = "./tests/wasm/element.js")]
+#[wasm_bindgen(module = "/tests/wasm/element.js")]
 extern "C" {
     fn new_style() -> HtmlStyleElement;
 }

crates/web-sys/tests/wasm/table_element.rs

@@ -2,7 +2,7 @@ use wasm_bindgen::prelude::*;
 use wasm_bindgen_test::*;
 use web_sys::{HtmlTableCaptionElement, HtmlTableElement, HtmlTableSectionElement};
 
-#[wasm_bindgen(module = "./tests/wasm/element.js")]
+#[wasm_bindgen(module = "/tests/wasm/element.js")]
 extern "C" {
     fn new_table() -> HtmlTableElement;
     fn new_caption() -> HtmlTableCaptionElement;

crates/web-sys/tests/wasm/title_element.rs

@@ -2,7 +2,7 @@ use wasm_bindgen::prelude::*;
 use wasm_bindgen_test::*;
 use web_sys::HtmlTitleElement;
 
-#[wasm_bindgen(module = "./tests/wasm/element.js")]
+#[wasm_bindgen(module = "/tests/wasm/element.js")]
 extern "C" {
     fn new_title() -> HtmlTitleElement;
 }

crates/web-sys/tests/wasm/whitelisted_immutable_slices.rs

@@ -14,7 +14,7 @@ use wasm_bindgen::prelude::*;
 use wasm_bindgen_test::*;
 use web_sys::WebGlRenderingContext;
 
-#[wasm_bindgen(module = "./tests/wasm/element.js")]
+#[wasm_bindgen(module = "/tests/wasm/element.js")]
 extern "C" {
     fn new_webgl_rendering_context() -> WebGlRenderingContext;
 // TODO: Add a function to create another type to test here.

crates/web-sys/tests/wasm/xpath_result.rs

@@ -2,7 +2,7 @@ use wasm_bindgen::prelude::*;
 use wasm_bindgen_test::*;
 use web_sys::XPathResult;
 
-#[wasm_bindgen(module = "./tests/wasm/element.js")]
+#[wasm_bindgen(module = "/tests/wasm/element.js")]
 extern "C" {
     fn new_xpath_result() -> XPathResult;
 }

crates/webidl-tests/build.rs

@@ -21,14 +21,13 @@ fn main() {
 
         let out_file = out_dir.join(path.file_name().unwrap()).with_extension("rs");
 
-        let js_file = path.with_extension("js").canonicalize().unwrap();
         generated_rust.push_str(&format!(
             r#"
             pub mod import_script {{
                 use wasm_bindgen::prelude::*;
                 use wasm_bindgen_test::*;
 
-                #[wasm_bindgen(module = r"{}")]
+                #[wasm_bindgen(module = "/{}.js")]
                 extern "C" {{
                     fn not_actually_a_function{1}(x: &str);
                 }}
@@ -41,7 +40,7 @@ fn main() {
                 }}
             }}
         "#,
-            js_file.display(),
+            path.file_stem().unwrap().to_str().unwrap(),
             i
         ));
 

crates/webidl/src/lib.rs

@@ -272,7 +272,7 @@ impl<'src> FirstPassRecord<'src> {
     ) {
         let variants = &enum_.values.body.list;
         program.imports.push(backend::ast::Import {
-            module: None,
+            module: backend::ast::ImportModule::None,
             js_namespace: None,
             kind: backend::ast::ImportKind::Enum(backend::ast::ImportEnum {
                 vis: public(),
@@ -463,7 +463,7 @@ impl<'src> FirstPassRecord<'src> {
             self.append_required_features_doc(&import_function, &mut doc, extra);
             import_function.doc_comment = doc;
             module.imports.push(backend::ast::Import {
-                module: None,
+                module: backend::ast::ImportModule::None,
                 js_namespace: Some(raw_ident(self_name)),
                 kind: backend::ast::ImportKind::Function(import_function),
             });
@@ -539,7 +539,7 @@ impl<'src> FirstPassRecord<'src> {
         import_type.doc_comment = doc_comment;
 
         program.imports.push(backend::ast::Import {
-            module: None,
+            module: backend::ast::ImportModule::None,
             js_namespace: None,
             kind: backend::ast::ImportKind::Type(import_type),
         });

examples/import_js/src/lib.rs

@@ -1,6 +1,6 @@
 use wasm_bindgen::prelude::*;
 
-#[wasm_bindgen(module = "../defined-in-js")]
+#[wasm_bindgen(module = "/defined-in-js.js")]
 extern "C" {
     fn name() -> String;
 

examples/raytrace-parallel/.gitignore

@@ -0,0 +1,2 @@
+raytrace_parallel.js
+raytrace_parallel_bg.wasm

examples/without-a-bundler-no-modules/Cargo.toml

@@ -0,0 +1,21 @@
+[package]
+name = "without-a-bundler-no-modules"
+version = "0.1.0"
+authors = ["The wasm-bindgen Developers"]
+edition = "2018"
+
+[lib]
+crate-type = ["cdylib"]
+
+[dependencies]
+wasm-bindgen = "0.2.37"
+
+[dependencies.web-sys]
+version = "0.3.4"
+features = [
+  'Document',
+  'Element',
+  'HtmlElement',
+  'Node',
+  'Window',
+]

examples/without-a-bundler-no-modules/README.md

@@ -0,0 +1,21 @@
+# Without a Bundler Using `--no-modules`
+
+[View documentation for this example online][dox]
+
+[dox]: https://rustwasm.github.io/wasm-bindgen/examples/without-a-bundler-no-modules.html
+
+You can build the example locally with:
+
+```
+$ wasm-pack build --target no-modules
+```
+
+and then opening `index.html` in a browser should run the example!
+
+Note that this example is in contrast to the [without a bundler][wab] example
+which performs a similar purpose except it uses `--no-modules` instead of
+`--browser`. The main difference here is how the shim JS and module are loaded,
+where this example uses old-school `script` tags while `--browser` uses ES
+modules.
+
+[wab]: https://github.com/rustwasm/wasm-bindgen/tree/master/examples/without-a-bundler

examples/without-a-bundler-no-modules/index.html

@@ -0,0 +1,30 @@
+<html>
+  <head>
+    <meta content="text/html;charset=utf-8" http-equiv="Content-Type"/>
+  </head>
+  <body>
+    <!-- Include the JS generated by `wasm-pack build` -->
+    <script src='pkg/without_a_bundler_no_modules.js'></script>
+
+    <script type=module>
+      // Like with the `--browser` output the exports are immediately available
+      // but they won't work until we initialize the module. Unlike `--browser`,
+      // however, the globals are all stored on a `wasm_bindgen` global. The
+      // global itself is the initialization function and then the properties of
+      // the global are all the exported functions.
+      //
+      // Note that the name `wasm_bindgen` can be configured with the
+      // `--no-modules-global` CLI flag
+      const { add } = wasm_bindgen;
+
+      async function run() {
+        await wasm_bindgen('./pkg/without_a_bundler_no_modules_bg.wasm');
+
+        const result = add(1, 2);
+        console.log(`1 + 2 = ${result}`);
+      }
+
+      run();
+    </script>
+  </body>
+</html>

examples/without-a-bundler-no-modules/src/lib.rs

@@ -0,0 +1,24 @@
+use wasm_bindgen::prelude::*;
+
+// Called when the wasm module is instantiated
+#[wasm_bindgen(start)]
+pub fn main() -> Result<(), JsValue> {
+    // Use `web_sys`'s global `window` function to get a handle on the global
+    // window object.
+    let window = web_sys::window().expect("no global `window` exists");
+    let document = window.document().expect("should have a document on window");
+    let body = document.body().expect("document should have a body");
+
+    // Manufacture the element we're gonna append
+    let val = document.create_element("p")?;
+    val.set_inner_html("Hello from Rust!");
+
+    body.append_child(&val)?;
+
+    Ok(())
+}
+
+#[wasm_bindgen]
+pub fn add(a: u32, b: u32) -> u32 {
+    a + b
+}

examples/without-a-bundler/README.md

@@ -7,7 +7,11 @@
 You can build the example locally with:
 
 ```
-$ wasm-pack build --target no-modules
+$ cargo build --target wasm32-unknown-unknown --release
+$ cargo run -p wasm-bindgen-cli --bin wasm-bindgen -- \
+  ../../target/wasm32-unknown-unknown/release/without_a_bundler.wasm \
+  --out-dir pkg \
+  --browser
 ```
 
 and then opening `index.html` in a browser should run the example!

examples/without-a-bundler/build.sh

@@ -0,0 +1,15 @@
+#!/bin/sh
+
+set -ex
+
+# Note that typically we'd use `wasm-pack` to build the crate, but the
+# `--browser` flag is very new to `wasm-bindgen` and as such doesn't have
+# support in `wasm-pack` yet. Support will be added soon though!
+
+cargo build --target wasm32-unknown-unknown --release
+cargo run --manifest-path ../../crates/cli/Cargo.toml \
+    --bin wasm-bindgen -- \
+    ../../target/wasm32-unknown-unknown/release/without_a_bundler.wasm --out-dir pkg \
+    --browser
+
+python3 -m http.server

examples/without-a-bundler/index.html

@@ -3,33 +3,29 @@
     <meta content="text/html;charset=utf-8" http-equiv="Content-Type"/>
   </head>
   <body>
-    <!--
-      This is the JS generated by the `wasm-pack` build command
-
-      The script here will define a `wasm_bindgen` global where all
-      functionality can be accessed such as instantiation and the actual
-      functions (examples below).
-
-      You can customize the name of the file here with the `out-name` CLI flag
-      to `wasm-bindgen`. You can also customize the name of the global exported
-      here with the `no-modules-global` flag.
-    -->
-    <script src='./pkg/without_a_bundler.js'></script>
-
-    <script>
-      // Import functionality from the wasm module, but note that it's not quite
-      // ready to be used just yet.
-      const { add } = wasm_bindgen;
+    <!-- Note the usage of `type=module` here as this is an ES6 module -->
+    <script type="module">
+      // Use ES module import syntax to import functionality from the module
+      // that we have compiled.
+      //
+      // Note that the `default` import is an initialization function which
+      // will "boot" the module and make it ready to use. Currently browsers
+      // don't support natively imported WebAssembly as an ES module, but
+      // eventually the manual initialization won't be required!
+      import { add, default as init } from './pkg/without_a_bundler.js';
 
       async function run() {
         // First up we need to actually load the wasm file, so we use the
-        // exported global to inform it where the wasm file is located on the
-        // server, and then we wait on the returned promies to wait for the
+        // default export to inform it where the wasm file is located on the
+        // server, and then we wait on the returned promise to wait for the
         // wasm to be loaded.
         //
         // Note that instead of a string here you can also pass in an instance
         // of `WebAssembly.Module` which allows you to compile your own module.
-        await wasm_bindgen('./pkg/without_a_bundler_bg.wasm');
+        // Also note that the promise, when resolved, yields the wasm module's
+        // exports which is the same as importing the `*_bg` module in other
+        // modes
+        await init('./pkg/without_a_bundler_bg.wasm');
 
         // And afterwards we can use all the functionality defined in wasm.
         const result = add(1, 2);

guide/src/SUMMARY.md

@@ -27,6 +27,7 @@
   - [web-sys: A TODO MVC App](./examples/todomvc.md)
 - [Reference](./reference/index.md)
   - [Deployment](./reference/deployment.md)
+  - [JS snippets](./reference/js-snippets.md)
   - [Passing Rust Closures to JS](./reference/passing-rust-closures-to-js.md)
   - [Receiving JS Closures in Rust](./reference/receiving-js-closures-in-rust.md)
   - [`Promise`s and `Future`s](./reference/js-promises-and-rust-futures.md)

guide/src/examples/without-a-bundler.md

@@ -4,12 +4,15 @@
 
 [code]: https://github.com/rustwasm/wasm-bindgen/tree/master/examples/without-a-bundler
 
-This example shows how the `--no-modules` flag can be used load code in a
+This example shows how the `--browser` flag can be used load code in a
 browser directly. For this deployment strategy bundlers like Webpack are not
 required. For more information on deployment see the [dedicated
 documentation][deployment].
 
-First let's take a look at the code and see how when we're using `--no-modules`
+> **Note**: the `--browser` flag is quite new to `wasm-bindgen`, and does not
+> currently have support in `wasm-pack` yet. Support will be added soon though!
+
+First let's take a look at the code and see how when we're using `--browser`
 we're not actually losing any functionality!
 
 ```rust
@@ -22,7 +25,33 @@ Otherwise the rest of the deployment magic happens in `index.html`:
 {{#include ../../../examples/without-a-bundler/index.html}}
 ```
 
-And that's it! Be sure to read up on the [deployment options][deployment] to see what it
-means to deploy without a bundler.
+And that's it! Be sure to read up on the [deployment options][deployment] to see
+what it means to deploy without a bundler.
 
 [deployment]: ../reference/deployment.html
+
+## Using the older `--no-modules`
+
+[View full source code][code]
+
+[code]: https://github.com/rustwasm/wasm-bindgen/tree/master/examples/without-a-bundler-no-modules
+
+The older version of using `wasm-bindgen` without a bundler is to use the
+`--no-modules` flag to the `wasm-bindgen` CLI. This corresponds to `--target
+no-modules` in `wasm-pack`.
+
+While similar to the newer `--browser`, the `--no-modules` flag has a few
+caveats:
+
+* It does not support [local JS snippets][snippets]
+* It does not generate an ES module
+
+With that in mind the main difference is how the wasm/JS code is loaded, and
+here's an example of loading the output of `wasm-pack` for the same module as
+above.
+
+```html
+{{#include ../../../examples/without-a-bundler-no-modules/index.html}}
+```
+
+[snippets]: ../reference/js-snippets.html

guide/src/reference/deployment.md

@@ -29,26 +29,29 @@ necessary.
 
 If you're not using a bundler but you're still running code in a web browser,
 `wasm-bindgen` still supports this! For this use case you'll want to use the
-`--no-modules` flag. You can check out a [full example][nomex] in the
+`--browser` flag. You can check out a [full example][nomex] in the
 documentation, but the highlights of this output are:
 
-* When using `wasm-pack` you'll pass `--target no-modules`, and when using
-  `wasm-bindgen` directly you'll pass `--no-modules`.
+* When using `wasm-bindgen` directly you'll pass `--browser`.
 * The output can natively be included on a web page, and doesn't require any
-  further postprocessing.
-* The `--no-modules` mode is not able to use NPM dependencies nor local JS
-  snippets (both currently [proposed][rfc1] [features][rfc2])
+  further postprocessing. The output is included as an ES module.
+* The `--browser` mode is not able to use NPM dependencies.
 * You'll want to review the [browser requirements] for `wasm-bindgen` because
   no polyfills will be available.
 
+> **Note**: currently `--browser` is not supported in `wasm-pack` because it is
+> a very recent addition to `wasm-bindgen`, but support will be added soon!
+
 [nomex]: ../examples/without-a-bundler.html
 [rfc1]: https://github.com/rustwasm/rfcs/pull/6
 [rfc2]: https://github.com/rustwasm/rfcs/pull/8
 [browser requirements]: browser-support.html
 
-Despite these limitations almost all code today is compatible with
-`--no-modules`, but this area is actively being worked on to improve the
-experience so the experience here may be tweaked over time!
+The `wasm-bindgen` CLI also supports an output mode called `--no-modules` which
+is similar to `--browser` in that it requires manual initialization of the wasm
+and is intended to be included in web pages without any further postprocessing.
+See the [without a bundler example][nomex] for some more information about
+`--no-modules`, which corresponds to `--target no-modules` in `wasm-pack`.
 
 ## Node.js
 

guide/src/reference/js-snippets.md

@@ -0,0 +1,78 @@
+# JS Snippets
+
+Often when developing a crate you want to run on the web you'll want to include
+some JS code here and there. While [`js-sys`](https://docs.rs/js-sys) and
+[`web-sys`](https://docs.rs/web-sys) cover many needs they don't cover
+everything, so `wasm-bindgen` supports the ability to write JS code next to your
+Rust code and have it included in the final output artifact.
+
+To include a local JS file, you'll use the `#[wasm_bindgen(module)]` macro:
+
+```rust
+#[wasm_bindgen(module = "/js/foo.js")]
+extern "C" {
+    fn add(a: u32, b: u32) -> u32;
+}
+```
+
+This declaration indicates that all the functions contained in the `extern`
+block are imported from the file `/js/foo.js`, where the root is relative to the
+crate root (where `Cargo.toml` is located).
+
+The `/js/foo.js` file will make its way to the final output when `wasm-bindgen`
+executes, so you can use the `module` annotation in a library without having to
+worry users of your library!
+
+The JS file itself must be written with ES module syntax:
+
+```js
+export function add(a, b) {
+    return a + b;
+}
+```
+
+A full design of this feature can be found in [RFC 6] as well if you're
+interested!
+
+[RFC 6]: https://github.com/rustwasm/rfcs/pull/6
+
+### Using `inline_js`
+
+In addition to `module = "..."` if you're a macro author you also have the
+ability to use the `inline_js` attribute:
+
+```rust
+#[wasm_bindgen(inline_js = "export function add(a, b) { return a + b; }")]
+extern "C" {
+    fn add(a: u32, b: u32) -> u32;
+}
+```
+
+Using `inline_js` indicates that the JS module is specified inline in the
+attribute itself, and no files are loaded from the filesystem. They have the
+same limitations and caveats as when using `module`, but can sometimes be easier
+to generate for macros themselves. It's not recommended for hand-written code to
+make use of `inline_js` but instead to leverage `module` where possible.
+
+### Caveats
+
+While quite useful local JS snippets currently suffer from a few caveats which
+are important to be aware of. Many of these are temporary though!
+
+* Currently `import` statements are not supported in the JS file. This is a
+  restriction we may lift in the future once we settle on a good way to support
+  this. For now, though, js snippets must be standalone modules and can't import
+  from anything else.
+
+* Only `--browser` and the default bundler output mode are supported. To support
+  `--nodejs` we'd need to translate ES module syntax to CommonJS (this is
+  planned to be done, just hasn't been done yet). Additionally to support
+  `--no-modules` we'd have to similarly translate from ES modules to something
+  else.
+
+* Paths in `module = "..."` must currently start with `/`, or be rooted at the
+  crate root. It is intended to eventually support relative paths like `./` and
+  `../`, but it's currently believed that this requires more support in
+  the Rust `proc_macro` crate.
+
+As above, more detail about caveats can be found in [RFC 6].

src/anyref.rs

@@ -110,8 +110,11 @@ impl Slab {
 }
 
 fn internal_error(msg: &str) -> ! {
-    let msg = if cfg!(debug_assertions) { msg } else { "" };
-    super::throw_str(msg)
+    if cfg!(debug_assertions) {
+        super::throw_str(msg)
+    } else {
+        std::process::abort()
+    }
 }
 
 // Whoa, there's two `tl` modules here! That's currently intention, but for sort

tests/headless/main.rs

@@ -37,3 +37,5 @@ extern "C" {
 fn can_log_html_strings() {
     log("<script>alert('lol')</script>");
 }
+
+pub mod snippets;

tests/headless/snippets.rs

@@ -0,0 +1,58 @@
+use wasm_bindgen::prelude::*;
+use wasm_bindgen_test::*;
+
+#[wasm_bindgen(module = "/tests/headless/snippets1.js")]
+extern {
+    fn get_two() -> u32;
+    #[wasm_bindgen(js_name = get_stateful)]
+    fn get_stateful1() -> u32;
+}
+
+#[wasm_bindgen(module = "/tests/headless/snippets1.js")]
+extern {
+    #[wasm_bindgen(js_name = get_stateful)]
+    fn get_stateful2() -> u32;
+}
+
+#[wasm_bindgen_test]
+fn test_get_two() {
+    assert_eq!(get_two(), 2);
+}
+
+#[wasm_bindgen_test]
+fn stateful_deduplicated() {
+    assert_eq!(get_stateful1(), 1);
+    assert_eq!(get_stateful2(), 2);
+    assert_eq!(get_stateful1(), 3);
+    assert_eq!(get_stateful2(), 4);
+}
+
+#[wasm_bindgen(inline_js = "export function get_three() { return 3; }")]
+extern {
+    fn get_three() -> u32;
+}
+
+#[wasm_bindgen_test]
+fn test_get_three() {
+    assert_eq!(get_three(), 3);
+}
+
+#[wasm_bindgen(inline_js = "let a = 0; export function get() { a += 1; return a; }")]
+extern {
+    #[wasm_bindgen(js_name = get)]
+    fn duplicate1() -> u32;
+}
+
+#[wasm_bindgen(inline_js = "let a = 0; export function get() { a += 1; return a; }")]
+extern {
+    #[wasm_bindgen(js_name = get)]
+    fn duplicate2() -> u32;
+}
+
+#[wasm_bindgen_test]
+fn duplicate_inline_not_unified() {
+    assert_eq!(duplicate1(), 1);
+    assert_eq!(duplicate2(), 1);
+    assert_eq!(duplicate1(), 2);
+    assert_eq!(duplicate2(), 2);
+}

tests/headless/snippets1.js

@@ -0,0 +1,9 @@
+export function get_two() {
+  return 2;
+}
+
+let a = 0;
+export function get_stateful() {
+  a += 1;
+  return a;
+}