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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.
/*
* Copyright 2017 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.javascript.jscomp.Es6ToEs3Util.createType;
import static com.google.javascript.jscomp.Es6ToEs3Util.withType;
import com.google.common.base.Preconditions;
import com.google.javascript.jscomp.AbstractCompiler.MostRecentTypechecker;
import com.google.javascript.jscomp.parsing.parser.FeatureSet;
import com.google.javascript.jscomp.parsing.parser.FeatureSet.Feature;
import com.google.javascript.rhino.IR;
import com.google.javascript.rhino.JSDocInfo;
import com.google.javascript.rhino.Node;
import com.google.javascript.rhino.ObjectTypeI;
import com.google.javascript.rhino.Token;
import com.google.javascript.rhino.TypeI;
import com.google.javascript.rhino.TypeIRegistry;
import com.google.javascript.rhino.jstype.JSTypeNative;
/**
* Converts ES6 "for of" loops to ES5.
*
* @author [email protected] (Tyler Breisacher)
*/
public final class Es6ForOfConverter implements NodeTraversal.Callback, HotSwapCompilerPass {
private final AbstractCompiler compiler;
private static final FeatureSet transpiledFeatures = FeatureSet.BARE_MINIMUM.with(Feature.FOR_OF);
// addTypes indicates whether we should add type information when transpiling.
private final boolean addTypes;
private final TypeIRegistry registry;
private final TypeI unknownType;
private final TypeI stringType;
private final TypeI booleanType;
private static final String ITER_BASE = "$jscomp$iter$";
private static final String ITER_RESULT = "$jscomp$key$";
public Es6ForOfConverter(AbstractCompiler compiler) {
this.compiler = compiler;
// Only add type information if NTI has been run.
this.addTypes = MostRecentTypechecker.NTI.equals(compiler.getMostRecentTypechecker());
this.registry = compiler.getTypeIRegistry();
this.unknownType = createType(addTypes, registry, JSTypeNative.UNKNOWN_TYPE);
this.stringType = createType(addTypes, registry, JSTypeNative.STRING_TYPE);
this.booleanType = createType(addTypes, registry, JSTypeNative.BOOLEAN_TYPE);
}
@Override
public void process(Node externs, Node root) {
TranspilationPasses.processTranspile(compiler, externs, transpiledFeatures, this);
TranspilationPasses.processTranspile(compiler, root, transpiledFeatures, this);
TranspilationPasses.markFeaturesAsTranspiledAway(compiler, transpiledFeatures);
}
@Override
public void hotSwapScript(Node scriptRoot, Node originalRoot) {
TranspilationPasses.hotSwapTranspile(compiler, scriptRoot, transpiledFeatures, this);
TranspilationPasses.markFeaturesAsTranspiledAway(compiler, transpiledFeatures);
}
@Override
public boolean shouldTraverse(NodeTraversal t, Node n, Node parent) {
return true;
}
@Override
public void visit(NodeTraversal t, Node n, Node parent) {
switch (n.getToken()) {
case FOR_OF:
visitForOf(t, n, parent);
break;
default:
break;
}
}
private void visitForOf(NodeTraversal t, Node node, Node parent) {
Node variable = node.removeFirstChild();
Node iterable = node.removeFirstChild();
Node body = node.removeFirstChild();
TypeI typeParam = unknownType;
if (addTypes) {
// TODO(sdh): This is going to be null if the iterable is nullable or unknown. We might want
// to consider some way of unifying rather than simply looking at the nominal type.
ObjectTypeI iterableType = iterable.getTypeI().autobox().toMaybeObjectType();
if (iterableType != null) {
TypeIRegistry registry = compiler.getTypeIRegistry();
TypeI iterableBaseType = registry.getNativeType(JSTypeNative.ITERABLE_TYPE);
typeParam = iterableType.getInstantiatedTypeArgument(iterableBaseType);
}
}
TypeI iteratorType = createGenericType(JSTypeNative.ITERATOR_TYPE, typeParam);
TypeI iIterableResultType = createGenericType(JSTypeNative.I_ITERABLE_RESULT_TYPE, typeParam);
TypeI iteratorNextType =
addTypes ? iteratorType.toMaybeObjectType().getPropertyType("next") : null;
JSDocInfo varJSDocInfo = variable.getJSDocInfo();
Node iterName =
withType(IR.name(ITER_BASE + compiler.getUniqueNameIdSupplier().get()), iteratorType);
iterName.makeNonIndexable();
Node getNext =
withType(
IR.call(
withType(
IR.getprop(iterName.cloneTree(), withStringType(IR.string("next"))),
iteratorNextType)),
iIterableResultType);
String variableName;
Token declType;
if (variable.isName()) {
declType = Token.NAME;
variableName = variable.getQualifiedName();
} else {
Preconditions.checkState(NodeUtil.isNameDeclaration(variable),
"Expected var, let, or const. Got %s", variable);
declType = variable.getToken();
variableName = variable.getFirstChild().getQualifiedName();
}
Node iterResult = withType(IR.name(ITER_RESULT + variableName), iIterableResultType);
iterResult.makeNonIndexable();
Node call = Es6ToEs3Util.makeIterator(compiler, iterable);
if (addTypes) {
TypeI jscompType = t.getScope().getVar("$jscomp").getNode().getTypeI();
TypeI makeIteratorType = jscompType.toMaybeObjectType().getPropertyType("makeIterator");
call.getFirstChild().setTypeI(makeIteratorType);
call.getFirstFirstChild().setTypeI(jscompType);
}
Node init = IR.var(iterName.cloneTree(), withType(call, iteratorType));
Node initIterResult = iterResult.cloneTree();
initIterResult.addChildToFront(getNext.cloneTree());
init.addChildToBack(initIterResult);
Node cond =
withBooleanType(
IR.not(
withBooleanType(
IR.getprop(iterResult.cloneTree(), withStringType(IR.string("done"))))));
Node incr =
withType(IR.assign(iterResult.cloneTree(), getNext.cloneTree()), iIterableResultType);
Node declarationOrAssign;
if (declType == Token.NAME) {
declarationOrAssign =
withType(
IR.assign(
withType(IR.name(variableName).useSourceInfoFrom(variable), typeParam),
withType(
IR.getprop(iterResult.cloneTree(), withStringType(IR.string("value"))),
typeParam)),
typeParam);
declarationOrAssign.setJSDocInfo(varJSDocInfo);
declarationOrAssign = IR.exprResult(declarationOrAssign);
} else {
declarationOrAssign = new Node(
declType,
withType(IR.name(variableName).useSourceInfoFrom(variable.getFirstChild()), typeParam));
declarationOrAssign.getFirstChild().addChildToBack(
withType(
IR.getprop(iterResult.cloneTree(), withStringType(IR.string("value"))),
typeParam));
declarationOrAssign.setJSDocInfo(varJSDocInfo);
}
Node newBody = IR.block(declarationOrAssign, body).useSourceInfoFrom(body);
Node newFor = IR.forNode(init, cond, incr, newBody);
newFor.useSourceInfoIfMissingFromForTree(node);
parent.replaceChild(node, newFor);
compiler.reportChangeToEnclosingScope(newFor);
}
private TypeI createGenericType(JSTypeNative typeName, TypeI typeArg) {
return Es6ToEs3Util.createGenericType(addTypes, registry, typeName, typeArg);
}
private Node withStringType(Node n) {
return withType(n, stringType);
}
private Node withBooleanType(Node n) {
return withType(n, booleanType);
}
}