Make wrapper instanciation lazy

Author: pmdartus

lib/constructs/interface.js

@@ -501,6 +501,9 @@ class Interface {
   generateRequires() {
     this.requires.addRaw("impl", "utils.implSymbol");
     this.requires.addRaw("ctorRegistry", "utils.ctorRegistrySymbol");
+    this.requires.addRaw("wrapperSymbol", "utils.wrapperSymbol");
+    this.requires.addRaw("globalObjectSymbol", "utils.globalObjectSymbol");
+    this.requires.addRaw("createWrapperSymbol", "utils.createWrapperSymbol");
 
     if (this.idl.inheritance !== null) {
       this.requires.add(this.idl.inheritance);
@@ -1126,7 +1129,9 @@ class Interface {
 
   generateIface() {
     this.str += `
-      exports.create = function create(globalObject, constructorArgs, privateData) {
+      function createWrapper(implObject) {
+        const globalObject = implObject[globalObjectSymbol];
+
         if (globalObject[ctorRegistry] === undefined) {
           throw new Error('Internal error: invalid global object');
         }
@@ -1136,49 +1141,55 @@ class Interface {
           throw new Error('Internal error: constructor ${this.name} is not installed on the passed global object');
         }
 
-        let obj = Object.create(ctor.prototype);
-        obj = exports.setup(obj, globalObject, constructorArgs, privateData);
-        return obj;
-      };
-      exports.createImpl = function createImpl(globalObject, constructorArgs, privateData) {
-        const obj = exports.create(globalObject, constructorArgs, privateData);
-        return utils.implForWrapper(obj);
-      };
-      exports._internalSetup = function _internalSetup(obj) {
+        let wrapperObject = Object.create(ctor.prototype);
+        exports._internalSetup(wrapperObject);
     `;
 
-    if (this.idl.inheritance) {
+    if (this.isLegacyPlatformObj) {
       this.str += `
-        ${this.idl.inheritance}._internalSetup(obj);
+        wrapperObject = new Proxy(wrapperObject, proxyHandler);
       `;
     }
 
-    this.generateOnInstance();
-
     this.str += `
+        implObject[wrapperSymbol] = wrapperObject;
+        wrapperObject[impl] = implObject;
+        return wrapperObject;
       };
-      exports.setup = function setup(obj, globalObject, constructorArgs = [], privateData = {}) {
-        privateData.wrapper = obj;
+      exports.create = function create(globalObject, constructorArgs, privateData) {
+        const implObject = exports.createImpl(globalObject, constructorArgs, privateData);
+        return utils.wrapperForImpl(implObject);
+      };
+      exports.createImpl = function createImpl(globalObject, constructorArgs = [], privateData = {}) {
+        const implObject = new Impl.implementation(globalObject, constructorArgs, privateData);
 
-        exports._internalSetup(obj);
-        Object.defineProperty(obj, impl, {
-          value: new Impl.implementation(globalObject, constructorArgs, privateData),
-          configurable: true
-        });
+        implObject[wrapperSymbol] = null;
+        implObject[globalObjectSymbol] = globalObject;
+        implObject[createWrapperSymbol] = createWrapper;
+
+        return implObject;
+      };
+      exports.setup = function setup(wrapperObject, globalObject, constructorArgs = [], privateData = {}) {
+        const implObject = exports.createImpl(globalObject, constructorArgs, privateData);
+
+        implObject[wrapperSymbol] = wrapperObject;
+        wrapperObject[impl] = implObject;
+
+        exports._internalSetup(wrapperObject);
+
+        return wrapperObject;
+      };
+      exports._internalSetup = function _internalSetup(obj) {
     `;
 
-    if (this.isLegacyPlatformObj) {
+    if (this.idl.inheritance) {
       this.str += `
-        obj = new Proxy(obj, proxyHandler);
+        ${this.idl.inheritance}._internalSetup(obj);
       `;
     }
+    this.generateOnInstance();
 
     this.str += `
-        obj[impl][utils.wrapperSymbol] = obj;
-        if (Impl.init) {
-          Impl.init(obj[impl], privateData);
-        }
-        return obj;
       };
     `;
   }

lib/output/utils.js

@@ -11,6 +11,8 @@ function hasOwn(obj, prop) {
 
 const wrapperSymbol = Symbol("wrapper");
 const implSymbol = Symbol("impl");
+const globalObjectSymbol = Symbol("global object");
+const createWrapperSymbol = Symbol("create wrapper");
 const sameObjectCaches = Symbol("SameObject caches");
 const ctorRegistrySymbol = Symbol.for("[webidl2js]  constructor registry");
 
@@ -28,7 +30,16 @@ function getSameObject(wrapper, prop, creator) {
 }
 
 function wrapperForImpl(impl) {
-  return impl ? impl[wrapperSymbol] : null;
+  if (!impl) {
+    return null;
+  }
+
+  const wrapper = impl[wrapperSymbol];
+  if (wrapper === undefined || wrapper !== null) {
+    return wrapper;
+  }
+
+  return impl[createWrapperSymbol](impl);
 }
 
 function implForWrapper(wrapper) {
@@ -91,6 +102,8 @@ module.exports = exports = {
   hasOwn,
   wrapperSymbol,
   implSymbol,
+  globalObjectSymbol,
+  createWrapperSymbol,
   getSameObject,
   ctorRegistrySymbol,
   wrapperForImpl,