Add an option to detect node at runtime

Sometimes builds are done once and used in both the browser and in node, so add
an option to do runtime detection if necessary

crates/test-support/src/lib.rs

@@ -15,6 +15,7 @@ pub struct Project {
     files: Vec<(String, String)>,
     debug: bool,
     js: bool,
+    detect_node: bool,
 }
 
 pub fn project() -> Project {
@@ -28,6 +29,7 @@ pub fn project() -> Project {
     Project {
         debug: true,
         js: false,
+        detect_node: false,
         files: vec![
             ("Cargo.toml".to_string(), format!(r#"
                 [package]
@@ -130,6 +132,11 @@ impl Project {
         self
     }
 
+    pub fn detect_node(&mut self, detect_node: bool) -> &mut Project {
+        self.detect_node = detect_node;
+        self
+    }
+
     pub fn js(&mut self, js: bool) -> &mut Project {
         self.js = js;
         self
@@ -171,6 +178,7 @@ impl Project {
         cli::Bindgen::new()
             .input_path(&as_a_module)
             .nodejs(true)
+            .nodejs_runtime_detect(self.detect_node)
             .typescript(true)
             .debug(self.debug)
             .generate(&root)

crates/wasm-bindgen-cli-support/src/js.rs

@@ -517,9 +517,9 @@ impl<'a> Context<'a> {
             return
         }
         self.required_internal_exports.insert("__wbindgen_malloc");
-        if self.config.nodejs {
+        if self.config.nodejs_runtime_detect || self.config.nodejs {
             self.globals.push_str(&format!("
-                function passStringToWasm(arg) {{
+                function passStringToWasmNode(arg) {{
                     if (typeof(arg) !== 'string')
                         throw new Error('expected a string argument');
                     const buf = Buffer.from(arg);
@@ -529,11 +529,12 @@ impl<'a> Context<'a> {
                     return [ptr, len];
                 }}
             "));
-        } else {
+        }
+        if self.config.nodejs_runtime_detect || !self.config.nodejs {
             self.expose_text_encoder();
             self.expose_uint8_memory();
             self.globals.push_str(&format!("
-                function passStringToWasm(arg) {{
+                function passStringToWasmBrowser(arg) {{
                     if (typeof(arg) !== 'string')
                         throw new Error('expected a string argument');
                     const buf = textEncoder().encode(arg);
@@ -544,6 +545,18 @@ impl<'a> Context<'a> {
                 }}
             "));
         }
+
+        if self.config.nodejs_runtime_detect {
+            self.globals.push_str("
+                let passStringToWasm = passStringToWasmBrowser;
+                if (typeof window === 'undefined')
+                    passStringToWasm = passStringToWasmNode;
+            ");
+        } else if self.config.nodejs {
+            self.globals.push_str("const passStringToWasm = passStringToWasmNode;\n");
+        } else {
+            self.globals.push_str("const passStringToWasm = passStringToWasmBrowser;\n");
+        }
     }
 
     fn expose_pass_array8_to_wasm(&mut self) {
@@ -653,19 +666,20 @@ impl<'a> Context<'a> {
         if !self.exposed_globals.insert("get_string_from_wasm") {
             return
         }
-        if self.config.nodejs {
+        if self.config.nodejs_runtime_detect || self.config.nodejs {
             self.globals.push_str(&format!("
-                function getStringFromWasm(ptr, len) {{
+                function getStringFromWasmNode(ptr, len) {{
                     const buf = Buffer.from(wasm.memory.buffer).slice(ptr, ptr + len);
                     const ret = buf.toString();
                     return ret;
                 }}
             "));
-        } else {
+        }
+        if self.config.nodejs_runtime_detect || !self.config.nodejs {
             self.expose_text_decoder();
             self.expose_uint8_memory();
             self.globals.push_str(&format!("
-                function getStringFromWasm(ptr, len) {{
+                function getStringFromWasmBrowser(ptr, len) {{
                     const mem = getUint8Memory();
                     const slice = mem.slice(ptr, ptr + len);
                     const ret = textDecoder().decode(slice);
@@ -673,6 +687,18 @@ impl<'a> Context<'a> {
                 }}
             "));
         }
+
+        if self.config.nodejs_runtime_detect {
+            self.globals.push_str("
+                let getStringFromWasm = getStringFromWasmBrowser;
+                if (typeof window === 'undefined')
+                    getStringFromWasm = getStringFromWasmNode;
+            ");
+        } else if self.config.nodejs {
+            self.globals.push_str("const getStringFromWasm = getStringFromWasmNode;\n");
+        } else {
+            self.globals.push_str("const getStringFromWasm = getStringFromWasmBrowser;\n");
+        }
     }
 
     fn expose_get_array_js_value_from_wasm(&mut self) {

crates/wasm-bindgen-cli-support/src/lib.rs

@@ -17,6 +17,7 @@ pub mod wasm2es6js;
 pub struct Bindgen {
     path: Option<PathBuf>,
     nodejs: bool,
+    nodejs_runtime_detect: bool,
     debug: bool,
     typescript: bool,
 }
@@ -35,6 +36,7 @@ impl Bindgen {
         Bindgen {
             path: None,
             nodejs: false,
+            nodejs_runtime_detect: false,
             debug: false,
             typescript: false,
         }
@@ -50,6 +52,11 @@ impl Bindgen {
         self
     }
 
+    pub fn nodejs_runtime_detect(&mut self, detect: bool) -> &mut Bindgen {
+        self.nodejs_runtime_detect = detect;
+        self
+    }
+
     pub fn debug(&mut self, debug: bool) -> &mut Bindgen {
         self.debug = debug;
         self

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

@@ -21,6 +21,7 @@ Options:
     -h --help                Show this screen.
     --out-dir DIR            Output directory
     --nodejs                 Generate output for node.js, not the browser
+    --nodejs-runtime-detect  Detect at runtime whether we're in node or a browser
     --typescript             Output a TypeScript definition file
     --debug                  Include otherwise-extraneous debug checks in output
     -V --version             Print the version number of wasm-bindgen
@@ -29,6 +30,7 @@ Options:
 #[derive(Debug, Deserialize)]
 struct Args {
     flag_nodejs: bool,
+    flag_nodejs_runtime_detect: bool,
     flag_typescript: bool,
     flag_out_dir: Option<PathBuf>,
     flag_debug: bool,
@@ -54,6 +56,7 @@ fn main() {
     let mut b = Bindgen::new();
     b.input_path(&input)
      .nodejs(args.flag_nodejs)
+     .nodejs_runtime_detect(args.flag_nodejs_runtime_detect)
      .debug(args.flag_debug)
      .typescript(args.flag_typescript);
 

tests/api.rs

@@ -3,6 +3,7 @@ extern crate test_support;
 #[test]
 fn works() {
     test_support::project()
+        .detect_node(true)
         .file("src/lib.rs", r#"
             #![feature(proc_macro)]