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Closure Compiler is a JavaScript optimizing compiler. It parses your JavaScript, analyzes it, removes dead code and rewrites and minimizes what's left. It also checks syntax, variable references, and types, and warns about common JavaScript pitfalls. It is used in many of Google's JavaScript apps, including Gmail, Google Web Search, Google Maps, and Google Docs.

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/*
 * Copyright 2014 The Closure Compiler Authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.google.javascript.jscomp;

import static com.google.common.base.Preconditions.checkState;
import static com.google.javascript.jscomp.AstFactory.type;
import static com.google.javascript.jscomp.TranspilationUtil.CANNOT_CONVERT_YET;

import com.google.javascript.jscomp.parsing.parser.FeatureSet;
import com.google.javascript.jscomp.parsing.parser.FeatureSet.Feature;
import com.google.javascript.rhino.JSDocInfo;
import com.google.javascript.rhino.Node;

/**
 * Converts {@code super.method()} calls and adds constructors to any classes that lack them.
 *
 * 

This has to run before the main {@link Es6RewriteClass} pass. The super() constructor calls * are not converted here, but rather in {@link Es6ConvertSuperConstructorCalls}, which runs later. */ public final class Es6ConvertSuper extends NodeTraversal.AbstractPostOrderCallback implements CompilerPass { private final AbstractCompiler compiler; private final AstFactory astFactory; private final SynthesizeExplicitConstructors constructorSynthesizer; private static final FeatureSet FEATURES_TO_RUN_FOR = FeatureSet.BARE_MINIMUM.with(Feature.SUPER, Feature.CLASSES); public Es6ConvertSuper(AbstractCompiler compiler) { this.compiler = compiler; this.astFactory = compiler.createAstFactory(); this.constructorSynthesizer = new SynthesizeExplicitConstructors(compiler); } @Override public void visit(NodeTraversal t, Node n, Node parent) { if (n.isClass()) { constructorSynthesizer.synthesizeClassConstructorIfMissing(t, n); } else if (n.isSuper()) { visitSuper(n, parent); } } private boolean isInterface(Node classNode) { JSDocInfo classJsDocInfo = NodeUtil.getBestJSDocInfo(classNode); return classJsDocInfo != null && classJsDocInfo.isInterface(); } private void visitSuper(Node node, Node parent) { checkState(node.isSuper()); Node exprRoot = node; if (exprRoot.getParent().isGetElem() || exprRoot.getParent().isGetProp()) { exprRoot = exprRoot.getParent(); } Node enclosingMemberDef = NodeUtil.getEnclosingNode( exprRoot, (Node n) -> { switch (n.getToken()) { case MEMBER_FUNCTION_DEF: case GETTER_DEF: case SETTER_DEF: case COMPUTED_PROP: return true; default: return false; } }); if (parent.isCall()) { // super(...) visitSuperCall(node, parent, enclosingMemberDef); } else if (parent.isGetProp() || parent.isGetElem()) { if (parent.getFirstChild() == node) { if (parent.getParent().isCall() && NodeUtil.isInvocationTarget(parent)) { // super.something(...) or super['something'](..) visitSuperPropertyCall(node, parent, enclosingMemberDef); } else { // super.something or super['something'] visitSuperPropertyAccess(node, parent, enclosingMemberDef); } } else { // super.something used in some other way compiler.report( JSError.make( node, CANNOT_CONVERT_YET, "Only calls to super or to a method of super are supported.")); } } else if (parent.isNew()) { throw new IllegalStateException("This should never happen. Did Es6SuperCheck fail to run?"); } else { // some other use of super we don't support yet compiler.report( JSError.make( node, CANNOT_CONVERT_YET, "Only calls to super or to a method of super are supported.")); } } private void visitSuperCall(Node node, Node parent, Node enclosingMemberDef) { checkState(parent.isCall(), parent); checkState(node.isSuper(), node); Node clazz = NodeUtil.getEnclosingClass(node); Node superName = clazz.getSecondChild(); if (!superName.isQualifiedName()) { // This will be reported as an error in Es6ToEs3Converter. return; } if (NodeUtil.isEs6ConstructorMemberFunctionDef(enclosingMemberDef)) { // Calls to super() constructors will be transpiled by Es6ConvertSuperConstructorCalls later. if (node.isFromExterns() || isInterface(clazz)) { // If a class is defined in an externs file or as an interface, it's only a stub, not an // implementation that should be instantiated. // A call to super() shouldn't actually exist for these cases and is problematic to // transpile, so just drop it. Node enclosingStatement = NodeUtil.getEnclosingStatement(node); Node enclosingStatementParent = enclosingStatement.getParent(); enclosingStatement.detach(); compiler.reportChangeToEnclosingScope(enclosingStatementParent); } // Calls to super() constructors will be transpiled by Es6ConvertSuperConstructorCalls // later. return; } else { // super can only be directly called in a constructor throw new IllegalStateException("This should never happen. Did Es6SuperCheck fail to run?"); } } private void visitSuperPropertyCall(Node node, Node parent, Node enclosingMemberDef) { checkState(parent.isGetProp() || parent.isGetElem(), parent); checkState(node.isSuper(), node); Node grandparent = parent.getParent(); checkState(grandparent.isCall()); Node clazz = NodeUtil.getEnclosingClass(node); Node superName = clazz.getSecondChild(); if (!superName.isQualifiedName()) { // This will be reported as an error in Es6ToEs3Converter. return; } Node callTarget = parent; if (enclosingMemberDef.isStaticMember()) { Node expandedSuper = superName.cloneTree().srcrefTree(node); expandedSuper.setOriginalName("super"); node.replaceWith(expandedSuper); callTarget = astFactory.createGetPropWithUnknownType(callTarget.detach(), "call"); grandparent.addChildToFront(callTarget); Node thisNode = astFactory.createThis(type(clazz)); thisNode.makeNonIndexable(); // no direct correlation with original source thisNode.insertAfter(callTarget); grandparent.srcrefTreeIfMissing(parent); } else { // Replace super node to give // super.method(...) -> SuperClass.prototype.method(...) Node expandedSuper = astFactory.createPrototypeAccess(superName.cloneTree()).srcrefTree(node); expandedSuper.setOriginalName("super"); node.replaceWith(expandedSuper); // Set the 'this' object correctly for the call // SuperClass.prototype.method(...) -> SuperClass.prototype.method.call(this, ...) callTarget = astFactory.createGetPropWithUnknownType(callTarget.detach(), "call"); grandparent.addChildToFront(callTarget); Node thisNode = astFactory.createThisForEs6Class(clazz); thisNode.makeNonIndexable(); // no direct correlation with original source thisNode.insertAfter(callTarget); grandparent.putBooleanProp(Node.FREE_CALL, false); grandparent.srcrefTreeIfMissing(parent); } compiler.reportChangeToEnclosingScope(grandparent); } private void visitSuperPropertyAccess(Node node, Node parent, Node enclosingMemberDef) { checkState(parent.isGetProp() || parent.isGetElem(), parent); checkState(node.isSuper(), node); Node grandparent = parent.getParent(); if (NodeUtil.isLValue(parent)) { // We don't support assigning to a super property compiler.report(JSError.make(parent, CANNOT_CONVERT_YET, "assigning to a super property")); return; } Node clazz = NodeUtil.getEnclosingClass(node); Node superName = clazz.getSecondChild(); if (!superName.isQualifiedName()) { // This will be reported as an error in Es6ToEs3Converter. return; } if (enclosingMemberDef.isStaticMember()) { // super.prop -> SuperClass.prop Node expandedSuper = superName.cloneTree().srcrefTree(node); expandedSuper.setOriginalName("super"); node.replaceWith(expandedSuper); } else { // super.prop -> SuperClass.prototype.prop Node newprop = astFactory.createPrototypeAccess(superName.cloneTree()).srcrefTree(node); newprop.setOriginalName("super"); node.replaceWith(newprop); } compiler.reportChangeToEnclosingScope(grandparent); } @Override public void process(Node externs, Node root) { // Might need to synthesize constructors for ambient classes in .d.ts externs TranspilationPasses.processTranspile(compiler, externs, FEATURES_TO_RUN_FOR, this); TranspilationPasses.processTranspile(compiler, root, FEATURES_TO_RUN_FOR, this); // TODO(rishipal): mark super feature as transpiled away } }





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