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/*
* Copyright 2016 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.checkArgument;
import static com.google.common.base.Preconditions.checkState;
import static com.google.javascript.jscomp.Es6ToEs3Util.CANNOT_CONVERT;
import com.google.javascript.jscomp.ExpressionDecomposer.DecompositionType;
import com.google.javascript.jscomp.deps.ModuleNames;
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.jstype.JSType;
import java.util.ArrayDeque;
import java.util.Deque;
/**
* Extracts ES6 classes defined in function calls to local constants.
*
* Example: Before: foo(class { constructor() {} }); After:
* const $jscomp$classdecl$var0 = class { constructor() {} };
* foo($jscomp$classdecl$var0);
*
*
*
This must be done before {@link Es6RewriteClass}, because that pass only handles classes that
* are declarations or simple assignments.
*
* @see Es6RewriteClass#visitClass(NodeTraversal, Node, Node)
*/
public final class Es6ExtractClasses extends NodeTraversal.AbstractPostOrderCallback
implements CompilerPass {
static final String CLASS_DECL_VAR = "$classdecl$var";
private final AbstractCompiler compiler;
private final ExpressionDecomposer expressionDecomposer;
private int classDeclVarCounter = 0;
private static final FeatureSet features = FeatureSet.BARE_MINIMUM.with(Feature.CLASSES);
Es6ExtractClasses(AbstractCompiler compiler) {
this.compiler = compiler;
this.expressionDecomposer = compiler.createDefaultExpressionDecomposer();
}
@Override
public void process(Node externs, Node root) {
TranspilationPasses.processTranspile(
compiler, externs, features, this, new SelfReferenceRewriter());
TranspilationPasses.processTranspile(
compiler, root, features, this, new SelfReferenceRewriter());
}
@Override
public void visit(NodeTraversal t, Node n, Node parent) {
if (n.isClass() && shouldExtractClass(n)) {
extractClass(t, n);
}
}
private class SelfReferenceRewriter implements NodeTraversal.Callback {
private class ClassDescription {
Node nameNode;
String outerName;
ClassDescription(Node nameNode, String outerName) {
this.nameNode = nameNode;
this.outerName = outerName;
}
}
private final Deque classStack = new ArrayDeque<>();
private boolean needsInnerNameRewriting(Node classNode, Node parent) {
checkArgument(classNode.isClass());
return classNode.getFirstChild().isName() && parent.isName();
}
@Override
public boolean shouldTraverse(NodeTraversal t, Node n, Node parent) {
if (n.isClass() && needsInnerNameRewriting(n, parent)) {
classStack.addFirst(new ClassDescription(n.getFirstChild(), parent.getString()));
}
return true;
}
@Override
public void visit(NodeTraversal t, Node n, Node parent) {
switch (n.getToken()) {
case CLASS:
if (needsInnerNameRewriting(n, parent)) {
classStack.removeFirst();
n.getFirstChild().replaceWith(IR.empty().srcref(n.getFirstChild()));
compiler.reportChangeToEnclosingScope(n);
}
break;
case NAME:
maybeUpdateClassSelfRef(t, n);
break;
default:
break;
}
}
private void maybeUpdateClassSelfRef(NodeTraversal t, Node nameNode) {
for (ClassDescription klass : classStack) {
if (nameNode != klass.nameNode && nameNode.matchesQualifiedName(klass.nameNode)) {
Var var = t.getScope().getVar(nameNode.getString());
if (var != null && var.getNameNode() == klass.nameNode) {
Node newNameNode =
IR.name(klass.outerName).setJSType(nameNode.getJSType()).srcref(nameNode);
nameNode.replaceWith(newNameNode);
compiler.reportChangeToEnclosingScope(newNameNode);
return;
}
}
}
}
}
private boolean shouldExtractClass(Node classNode) {
Node parent = classNode.getParent();
boolean isAnonymous = classNode.getFirstChild().isEmpty();
if (NodeUtil.isClassDeclaration(classNode)
|| (isAnonymous && parent.isName())
|| (isAnonymous
&& parent.isAssign()
&& parent.getFirstChild().isQualifiedName()
&& parent.getParent().isExprResult())) {
// No need to extract. Handled directly by Es6ToEs3Converter.ClassDeclarationMetadata#create.
return false;
}
if (expressionDecomposer.canExposeExpression(classNode) == DecompositionType.UNDECOMPOSABLE) {
compiler.report(
JSError.make(classNode, CANNOT_CONVERT, "class expression that cannot be extracted"));
return false;
}
return true;
}
private void extractClass(NodeTraversal t, Node classNode) {
if (expressionDecomposer.canExposeExpression(classNode) == DecompositionType.DECOMPOSABLE) {
expressionDecomposer.maybeExposeExpression(classNode);
}
Node parent = classNode.getParent();
String name = ModuleNames.fileToJsIdentifier(classNode.getStaticSourceFile().getName())
+ CLASS_DECL_VAR
+ (classDeclVarCounter++);
JSDocInfo info = NodeUtil.getBestJSDocInfo(classNode);
Node statement = NodeUtil.getEnclosingStatement(parent);
JSType classType = classNode.getJSType();
checkState(!compiler.hasTypeCheckingRun() || classType != null);
// class name node used as LHS in newly created assignment
Node classNameLhs = IR.name(name).setJSType(classType);
// class name node that replaces the class literal in the original statement
Node classNameRhs = classNameLhs.cloneTree();
classNode.replaceWith(classNameRhs);
Node classDeclaration = IR.constNode(classNameLhs, classNode).srcrefTreeIfMissing(classNode);
NodeUtil.addFeatureToScript(t.getCurrentScript(), Feature.CONST_DECLARATIONS, compiler);
classDeclaration.setJSDocInfo(JSDocInfo.Builder.maybeCopyFrom(info).build());
classDeclaration.insertBefore(statement);
// If the original statement was a variable declaration or qualified name assignment like
// like these:
// var ClassName = class {...
// OR
// some.qname.ClassName = class {...
//
// We will have changed the original statement to
//
// var ClassName = generatedName;
// OR
// some.qname.ClassName = generatedName;
//
// This is creating a type alias for a class, but since there's no literal class on the RHS,
// it doesn't look like one. Add at-constructor JSDoc to make it clear that this is happening.
//
// This was added to fix a specific problem where the original definition was for an abstract
// class, so its JSDoc included at-abstract.
// This caused ClosureCodeRemoval to think this rewritten assignment was a removable abstract
// method definition instead of the definition of an abstract class.
//
// TODO(b/117292942): Make ClosureCodeRemoval smarter so this hack isn't necessary to
// prevent incorrect removal of assignments.
if (NodeUtil.isNameDeclaration(statement)
&& statement.hasOneChild()
&& statement.getOnlyChild() == parent) {
// var ClassName = generatedName;
addAtConstructor(statement);
} else if (statement.isExprResult()) {
Node expr = statement.getOnlyChild();
if (expr.isAssign()
&& expr.getFirstChild().isQualifiedName()
&& expr.getSecondChild() == classNameRhs) {
// some.qname.ClassName = generatedName;
addAtConstructor(expr);
}
}
compiler.reportChangeToEnclosingScope(classDeclaration);
}
/**
* Add at-constructor to the JSDoc of the given node.
*
* @param node
*/
private void addAtConstructor(Node node) {
JSDocInfo.Builder builder = JSDocInfo.Builder.maybeCopyFrom(node.getJSDocInfo());
builder.recordConstructor();
node.setJSDocInfo(builder.build());
}
}