Add support for variadic arguments in WebIDL

crates/cli-support/src/js/rust2js.rs

@@ -547,13 +547,26 @@ impl<'a, 'b> Rust2Js<'a, 'b> {
                 return Err(failure::err_msg("a function with no arguments cannot be variadic"));
             }
             let last_arg = self.js_arguments.len() - 1; // check implies >= 0
-            self.ret_expr.replace(
-                "JS",
-                &format!("{}({}, ...{})",
-                         invoc,
-                         self.js_arguments[..last_arg].join(", "),
-                         self.js_arguments[last_arg])
-            )
+            if self.js_arguments.len() != 1 {
+                self.ret_expr.replace(
+                    "JS",
+                    &format!(
+                        "{}({}, ...{})",
+                        invoc,
+                        self.js_arguments[..last_arg].join(", "),
+                        self.js_arguments[last_arg],
+                    )
+                )
+            } else {
+                self.ret_expr.replace(
+                    "JS",
+                    &format!(
+                        "{}(...{})",
+                        invoc,
+                        self.js_arguments[last_arg],
+                    )
+                )
+            }
         } else {
             self.ret_expr.replace(
                 "JS",

crates/webidl-tests/simple.js

@@ -110,6 +110,13 @@ global.OptionalAndUnionArguments = class OptionalAndUnionArguments {
   }
 };
 
+global.Variadic = class Variadic {
+  constructor() {}
+  sum(...values) {
+    return values.reduce((a, b) => a + b, 0);
+  }
+};
+
 global.PartialInterface = class PartialInterface {
   get un() {
     return 1;

crates/webidl-tests/simple.rs

@@ -90,6 +90,12 @@ fn optional_and_union_arguments() {
     assert_eq!(f.m_with_b_and_str_and_opt_bool("abc", false, "5", Some(true)), "string, abc, boolean, false, string, 5, boolean, true");
 }
 
+#[wasm_bindgen_test]
+fn variadic() {
+    let f = Variadic::new().unwrap();
+    assert_eq!(f.sum(Box::new([1, 2, 3, 4, 5])), 15);
+}
+
 #[wasm_bindgen_test]
 fn unforgeable_is_structural() {
     let f = Unforgeable::new().unwrap();

crates/webidl-tests/simple.webidl

@@ -57,6 +57,11 @@ interface OptionalAndUnionArguments {
   );
 };
 
+[Constructor()]
+interface Variadic {
+  short sum(short... values);
+};
+
 [Constructor()]
 interface Unforgeable {
   [Unforgeable] readonly attribute short uno;

crates/webidl/src/first_pass.rs

@@ -89,18 +89,19 @@ pub(crate) struct OperationData<'src> {
     pub(crate) is_static: bool,
 }
 
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 pub(crate) struct Signature<'src> {
     pub(crate) args: Vec<Arg<'src>>,
     pub(crate) ret: weedle::types::ReturnType<'src>,
     pub(crate) attrs: &'src Option<ExtendedAttributeList<'src>>,
 }
 
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 pub(crate) struct Arg<'src> {
     pub(crate) name: &'src str,
     pub(crate) ty: &'src weedle::types::Type<'src>,
     pub(crate) optional: bool,
+    pub(crate) variadic: bool,
 }
 
 /// Implemented on an AST node to populate the `FirstPassRecord` struct.
@@ -259,19 +260,17 @@ fn first_pass_operation<'src>(
     };
     let mut args = Vec::with_capacity(arguments.len());
     for argument in arguments {
-        let arg = match argument {
-            Argument::Single(single) => single,
-            Argument::Variadic(v) => {
-                warn!("Unsupported variadic argument {} in {}",
-                      v.identifier.0,
-                      self_name);
-                return
-            }
+        let (name, ty, optional, variadic) = match argument {
+            Argument::Single(single) =>
+                (single.identifier.0, &single.type_.type_, single.optional.is_some(), false),
+            Argument::Variadic(variadic) =>
+                (variadic.identifier.0, &variadic.type_, false, true),
         };
         args.push(Arg {
-            name: arg.identifier.0,
-            ty: &arg.type_.type_,
-            optional: arg.optional.is_some(),
+            name,
+            ty,
+            optional,
+            variadic,
         });
     }
     for id in ids {

crates/webidl/src/lib.rs

@@ -137,7 +137,7 @@ fn builtin_idents() -> BTreeSet<Ident> {
     BTreeSet::from_iter(
         vec![
             "str", "char", "bool", "JsValue", "u8", "i8", "u16", "i16", "u32", "i32", "u64", "i64",
-            "usize", "isize", "f32", "f64", "Result", "String", "Vec", "Option",
+            "usize", "isize", "f32", "f64", "Result", "String", "Box", "Vec", "Option",
             "ArrayBuffer", "Object", "Promise",
         ].into_iter()
             .map(|id| proc_macro2::Ident::new(id, proc_macro2::Span::call_site())),

crates/webidl/src/util.rs

@@ -172,6 +172,24 @@ pub(crate) fn slice_ty(t: syn::Type) -> syn::Type {
     }.into()
 }
 
+/// From `T` create `Box<T>`.
+pub(crate) fn box_ty(t: syn::Type) -> syn::Type {
+    let arguments = syn::PathArguments::AngleBracketed(syn::AngleBracketedGenericArguments {
+        colon2_token: None,
+        lt_token: Default::default(),
+        args: FromIterator::from_iter(vec![
+            syn::GenericArgument::Type(t),
+        ]),
+        gt_token: Default::default(),
+    });
+
+    let ident = raw_ident("Box");
+    let seg = syn::PathSegment { ident, arguments };
+    let path: syn::Path = seg.into();
+    let ty = syn::TypePath { qself: None, path };
+    ty.into()
+}
+
 /// From `T` create `Vec<T>`.
 pub(crate) fn vec_ty(t: syn::Type) -> syn::Type {
     let arguments = syn::PathArguments::AngleBracketed(syn::AngleBracketedGenericArguments {
@@ -223,6 +241,7 @@ impl<'src> FirstPassRecord<'src> {
         kind: backend::ast::ImportFunctionKind,
         structural: bool,
         catch: bool,
+        variadic: bool,
         doc_comment: Option<String>,
     ) -> Option<backend::ast::ImportFunction> where 'src: 'a {
         // Convert all of the arguments from their IDL type to a `syn` type,
@@ -245,7 +264,9 @@ impl<'src> FirstPassRecord<'src> {
         } else {
             Vec::with_capacity(idl_arguments.size_hint().0)
         };
-        for (argument_name, idl_type) in idl_arguments {
+        let idl_arguments: Vec<_> = idl_arguments.collect();
+        let arguments_count = idl_arguments.len();
+        for (i, (argument_name, idl_type)) in idl_arguments.into_iter().enumerate() {
             let syn_type = match idl_type.to_syn_type(TypePosition::Argument) {
                 Some(t) => t,
                 None => {
@@ -257,6 +278,20 @@ impl<'src> FirstPassRecord<'src> {
                     return None
                 }
             };
+            let syn_type = if variadic && i == arguments_count - 1 {
+                // Blacklist unsupported slice types
+                match idl_type {
+                    | IdlType::DomString
+                    | IdlType::ByteString
+                    | IdlType::UsvString => return None,
+
+                    IdlType::Interface(..) => return None,
+
+                    _ => box_ty(slice_ty(syn_type))
+                }
+            } else {
+                syn_type
+            };
             let argument_name = rust_ident(&argument_name.to_snake_case());
             arguments.push(simple_fn_arg(argument_name, syn_type));
         }
@@ -296,10 +331,10 @@ impl<'src> FirstPassRecord<'src> {
             },
             rust_name: rust_ident(rust_name),
             js_ret: js_ret.clone(),
-            variadic: false,
+            variadic,
             catch,
             structural,
-            shim:{
+            shim: {
                 let ns = match kind {
                     backend::ast::ImportFunctionKind::ScopedMethod { .. } |
                     backend::ast::ImportFunctionKind::Normal => "",
@@ -334,7 +369,8 @@ impl<'src> FirstPassRecord<'src> {
             kind,
             is_structural(attrs.as_ref(), container_attrs),
             throws(attrs),
-            Some(format!("The `{}` getter\n\n{}", name, mdn_doc(self_name, Some(name))))
+            false,
+            Some(format!("The `{}` getter\n\n{}", name, mdn_doc(self_name, Some(name)))),
         )
     }
 
@@ -360,7 +396,8 @@ impl<'src> FirstPassRecord<'src> {
             kind,
             is_structural(attrs.as_ref(), container_attrs),
             throws(attrs),
-            Some(format!("The `{}` setter\n\n{}", name, mdn_doc(self_name, Some(name))))
+            false,
+            Some(format!("The `{}` setter\n\n{}", name, mdn_doc(self_name, Some(name)))),
         )
     }
 
@@ -413,7 +450,14 @@ impl<'src> FirstPassRecord<'src> {
             let mut idl_args = Vec::with_capacity(signature.args.len());
             for (i, arg) in signature.args.iter().enumerate() {
                 if arg.optional {
-                    assert!(signature.args[i..].iter().all(|a| a.optional));
+                    assert!(
+                        signature
+                            .args[i..]
+                            .iter()
+                            .all(|arg| arg.optional || arg.variadic),
+                        "Not optional or variadic argument after optional argument: {:?}",
+                        signature.args,
+                    );
                     signatures.push((signature, idl_args.clone()));
                 }
                 match arg.ty.to_idl_type(self) {
@@ -569,6 +613,8 @@ impl<'src> FirstPassRecord<'src> {
                 kind.clone(),
                 force_structural || is_structural(signature.orig.attrs.as_ref(), container_attrs),
                 force_throws || throws(&signature.orig.attrs),
+                signature.args.len() == signature.orig.args.len()
+                    && signature.orig.args.last().map(|arg| arg.variadic).unwrap_or(false),
                 None,
             ));
         }