feat: add support for parsing async iterable<T> type

Author: lucacasonato

README.md

@@ -236,7 +236,7 @@ attached to a field called `idlType`:
 Where the fields are as follows:
 
 * `type`: String indicating where this type is used. Can be `null` if not applicable.
-* `generic`: String indicating the generic type (e.g. "Promise", "sequence").
+* `generic`: String indicating the generic type (e.g. "Promise", "sequence", "async iterable").
 * `idlType`: String indicating the type name, or array of subtypes if the type is
   generic or a union.
 * `nullable`: `true` if the type is nullable.

lib/productions/attribute.js

@@ -75,7 +75,9 @@ export class Attribute extends Base {
     yield* this.extAttrs.validate(defs);
     yield* this.idlType.validate(defs);
 
-    if (["sequence", "record"].includes(this.idlType.generic)) {
+    if (
+      ["async iterable", "sequence", "record"].includes(this.idlType.generic)
+    ) {
       const message = `Attributes cannot accept ${this.idlType.generic} types.`;
       yield validationError(
         this.tokens.name,

lib/productions/callback.js

@@ -5,6 +5,7 @@ import {
   unescape,
   autoParenter,
 } from "./helpers.js";
+import { validationError } from "../error.js";
 
 export class CallbackFunction extends Base {
   /**
@@ -44,6 +45,18 @@ export class CallbackFunction extends Base {
 
   *validate(defs) {
     yield* this.extAttrs.validate(defs);
+    for (const arg of this.arguments) {
+      yield* arg.validate(defs);
+      if (arg.idlType.generic === "async iterable") {
+        const message = `Callback function arguments can not be ${arg.idlType.generic} types.`;
+        yield validationError(
+          arg.tokens.name,
+          arg,
+          "operation-return-invalid-type",
+          message,
+        );
+      }
+    }
     yield* this.idlType.validate(defs);
   }
 

lib/productions/iterable.js

@@ -68,9 +68,19 @@ export class IterableLike extends Base {
       }
     }
 
-    tokens.termination =
-      tokeniser.consume(";") ||
+    tokens.termination = tokeniser.consume(";");
+    if (
+      !tokens.termination &&
+      tokens.async &&
+      tokens.base.value === "iterable"
+    ) {
+      // Instead of a missing semicolon, this could be an async iterable return
+      // type for a regular operation. Let's bail out early in that case.
+      tokeniser.unconsume(start_position);
+      return;
+    } else if (!tokens.termination) {
       tokeniser.error(`Missing semicolon after ${type} declaration`);
+    }
 
     return ret.this;
   }

lib/productions/type.js

@@ -16,7 +16,9 @@ import { ExtendedAttributes } from "./extended-attributes.js";
  * @param {string} typeName
  */
 function generic_type(tokeniser, typeName) {
+  const prevPosition = tokeniser.position;
   const base = tokeniser.consume(
+    "async",
     "FrozenArray",
     "ObservableArray",
     "Promise",
@@ -29,6 +31,14 @@ function generic_type(tokeniser, typeName) {
   const ret = autoParenter(
     new Type({ source: tokeniser.source, tokens: { base } }),
   );
+  if (base.value === "async") {
+    ret.tokens.async = base;
+    ret.tokens.base = tokeniser.consume("iterable");
+    if (!ret.tokens.base) {
+      tokeniser.unconsume(prevPosition); // unconsume the "async" token
+      return;
+    }
+  }
   ret.tokens.open =
     tokeniser.consume("<") ||
     tokeniser.error(`No opening bracket after ${base.value}`);
@@ -42,6 +52,7 @@ function generic_type(tokeniser, typeName) {
       ret.subtype.push(subtype);
       break;
     }
+    case "async":
     case "sequence":
     case "FrozenArray":
     case "ObservableArray": {
@@ -169,6 +180,8 @@ export class Type extends Base {
 
   get generic() {
     if (this.subtype.length && this.tokens.base) {
+      if (this.tokens.base.value === "iterable" && this.tokens.async)
+        return "async iterable";
       return this.tokens.base.value;
     }
     return "";
@@ -259,6 +272,7 @@ for more information.`;
     const type_body = () => {
       if (this.union || this.generic) {
         return w.ts.wrap([
+          w.token(this.tokens.async, w.ts.generic),
           w.token(this.tokens.base, w.ts.generic),
           w.token(this.tokens.open),
           ...this.subtype.map((t) => t.write(w)),

test/invalid/baseline/invalid-attribute.txt

@@ -1,21 +1,24 @@
 (attr-invalid-type) Validation error at line 3 in invalid-attribute.webidl, inside `interface sequenceAsAttribute -> attribute invalid`:
   attribute sequence<short> invalid;
                             ^ Attributes cannot accept sequence types.
-(attr-invalid-type) Validation error at line 9 in invalid-attribute.webidl, inside `interface recordAsAttribute -> attribute invalid`:
+(attr-invalid-type) Validation error at line 9 in invalid-attribute.webidl, inside `interface asyncIterableAsAttribute -> attribute invalid`:
+ async iterable<short> invalid;
+                       ^ Attributes cannot accept async iterable types.
+(attr-invalid-type) Validation error at line 15 in invalid-attribute.webidl, inside `interface recordAsAttribute -> attribute invalid`:
 <DOMString, DOMString> invalid;
                        ^ Attributes cannot accept record types.
-(attr-invalid-type) Validation error at line 17 in invalid-attribute.webidl, inside `interface dictionaryAsAttribute -> attribute dict`:
+(attr-invalid-type) Validation error at line 23 in invalid-attribute.webidl, inside `interface dictionaryAsAttribute -> attribute dict`:
   attribute Dict dict;
             ^ Attributes cannot accept dictionary types.
-(attr-invalid-type) Validation error at line 18 in invalid-attribute.webidl, inside `interface dictionaryAsAttribute -> attribute dictUnion`:
+(attr-invalid-type) Validation error at line 24 in invalid-attribute.webidl, inside `interface dictionaryAsAttribute -> attribute dictUnion`:
   attribute (Dict or boolean) dictUnion
              ^ Attributes cannot accept dictionary types.
-(attr-invalid-type) Validation error at line 28 in invalid-attribute.webidl, inside `interface EnforceRangeInReadonlyAttribute -> attribute readOnlyAttr1`:
+(attr-invalid-type) Validation error at line 34 in invalid-attribute.webidl, inside `interface EnforceRangeInReadonlyAttribute -> attribute readOnlyAttr1`:
   readonly attribute [EnforceRange] long readOnlyAttr1;
                                     ^ Readonly attributes cannot accept [EnforceRange] extended attribute.
-(attr-invalid-type) Validation error at line 29 in invalid-attribute.webidl, inside `interface EnforceRangeInReadonlyAttribute -> attribute readOnlyAttr2`:
+(attr-invalid-type) Validation error at line 35 in invalid-attribute.webidl, inside `interface EnforceRangeInReadonlyAttribute -> attribute readOnlyAttr2`:
   readonly attribute [EnforceRange] GPUInt32In readOnlyAttr2;
                                     ^ Readonly attributes cannot accept [EnforceRange] extended attribute.
-(attr-invalid-type) Validation error at line 30 in invalid-attribute.webidl, inside `interface EnforceRangeInReadonlyAttribute -> attribute readOnlyAttr2`:
+(attr-invalid-type) Validation error at line 36 in invalid-attribute.webidl, inside `interface EnforceRangeInReadonlyAttribute -> attribute readOnlyAttr2`:
   readonly attribute GPUInt32 readOnlyAttr2;
                      ^ Readonly attributes cannot accept [EnforceRange] extended attribute.

test/invalid/baseline/invalid-callback-argument.txt

@@ -0,0 +1,3 @@
+(operation-return-invalid-type) Validation error at line 1 in invalid-callback-argument.webidl, inside `callback DoSomething -> argument bool`:
+async iterable<DOMString> bool);
+                          ^ Callback function arguments can not be async iterable types.

test/invalid/idl/invalid-attribute.webidl

@@ -4,6 +4,12 @@ interface sequenceAsAttribute {
   attribute (sequence<short> or boolean) invalidUnion; // TODO
 };
 
+[Exposed=Window]
+interface asyncIterableAsAttribute {
+  attribute async iterable<short> invalid;
+  attribute (async iterable<short> or boolean) invalidUnion; // TODO
+};
+
 [Exposed=Window]
 interface recordAsAttribute {
   attribute record<DOMString, DOMString> invalid;

test/invalid/idl/invalid-callback-argument.webidl

@@ -0,0 +1 @@
+callback DoSomething = Promise<DOMString> (async iterable<DOMString> bool);