Implement support for the [Exposed] extended attribute

README.md

@@ -454,6 +454,7 @@ webidl2js is implementing an ever-growing subset of the Web IDL specification. S
 - Variadic arguments
 - `[Clamp]`
 - `[EnforceRange]`
+- `[Exposed]`
 - `[LegacyArrayClass]`
 - `[LegacyUnenumerableNamedProperties]`
 - `[LegacyWindowAlias]`

lib/constructs/callback-interface.js

@@ -20,6 +20,25 @@ class CallbackInterface {
 
     this._analyzed = false;
     this._outputStaticProperties = new Map();
+
+    const exposed = utils.getExtAttr(this.idl.extAttrs, "Exposed");
+    if (this.idl.members.some(member => member.type === "const") && !exposed) {
+      throw new Error(`Callback interface ${this.name} with defined constants lacks the [Exposed] extended attribute`);
+    }
+
+    if (exposed) {
+      if (!exposed.rhs || (exposed.rhs.type !== "identifier" && exposed.rhs.type !== "identifier-list")) {
+        throw new Error(`[Exposed] must take an identifier or an identifier list in callback interface ${this.name}`);
+      }
+
+      if (exposed.rhs.type === "identifier") {
+        this.exposed = new Set([exposed.rhs.value]);
+      } else {
+        this.exposed = new Set(exposed.rhs.value.map(token => token.value));
+      }
+    } else {
+      this.exposed = new Set();
+    }
   }
 
   _analyzeMembers() {
@@ -178,14 +197,41 @@ class CallbackInterface {
   }
 
   generateInstall() {
+    if (this.constants.size > 0) {
+      this.str += `
+        const exposed = new Set([
+      `;
+
+      for (const globalName of this.exposed) {
+        this.str += `"${globalName}",\n`;
+      }
+
+      this.str += `
+        ]);
+      `;
+    }
+
     this.str += `
-      exports.install = function install(globalObject) {
+      exports.install = (globalObject, globalNames) => {
     `;
 
     if (this.constants.size > 0) {
       const { name } = this;
 
       this.str += `
+        let isExposed = false;
+
+        for (const globalName of globalNames) {
+          if (exposed.has(globalName)) {
+            isExposed = true;
+            break;
+          }
+        }
+
+        if (!isExposed) {
+          return;
+        }
+
         const ${name} = () => {
           throw new TypeError("Illegal invocation");
         };
@@ -234,4 +280,6 @@ class CallbackInterface {
   }
 }
 
+CallbackInterface.prototype.type = "callback interface";
+
 module.exports = CallbackInterface;

lib/constructs/interface.js

@@ -1463,7 +1463,47 @@ class Interface {
     const { idl, name } = this;
 
     this.str += `
-      exports.install = (globalObject, globalName) => {
+      const exposed = new Set([
+    `;
+
+    for (const globalName of this.exposed) {
+      this.str += `"${globalName}",\n`;
+    }
+
+    this.str += `
+      ]);
+
+      exports.install = (globalObject, globalNames) => {
+        let isExposed = false;
+    `;
+
+    if (this.legacyWindowAliases) {
+      this.str += "let isWindow = false;\n";
+    }
+
+    this.str += `
+        for (const globalName of globalNames) {
+          if (exposed.has(globalName)) {
+            isExposed = true;
+    `;
+
+    if (this.legacyWindowAliases) {
+      this.str += `
+            if (globalName === "Window") {
+              isWindow = true;
+            }
+      `;
+    } else {
+      this.str += "break;";
+    }
+
+    this.str += `
+          }
+        }
+
+        if (!isExposed) {
+          return;
+        }
     `;
 
     if (idl.inheritance) {
@@ -1500,7 +1540,7 @@ class Interface {
 
       if (this.legacyWindowAliases) {
         this.str += `
-          if (globalName === "Window") {
+          if (isWindow) {
         `;
 
         for (const legacyWindowAlias of this.legacyWindowAliases) {