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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. This binary checks for style issues such as incorrect or missing JSDoc usage, and missing goog.require() statements. It does not do more advanced checks such as typechecking.

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/*
 * Copyright 2010 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 com.google.common.base.Preconditions;
import com.google.common.collect.HashMultiset;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Multiset;
import com.google.javascript.jscomp.CompilerOptions.AliasTransformation;
import com.google.javascript.jscomp.CompilerOptions.AliasTransformationHandler;
import com.google.javascript.rhino.IR;
import com.google.javascript.rhino.JSDocInfo;
import com.google.javascript.rhino.JSDocInfoBuilder;
import com.google.javascript.rhino.Node;
import com.google.javascript.rhino.SourcePosition;
import com.google.javascript.rhino.Token;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import javax.annotation.Nullable;

/**
 * Process aliases in goog.scope blocks.
 *
 * 
 * goog.scope(function() {
 *   var dom = goog.dom;
 *   var DIV = dom.TagName.DIV;
 *
 *   dom.createElement(DIV);
 * });
 * 
* * should become * *
 * goog.dom.createElement(goog.dom.TagName.DIV);
 * 
* * The advantage of using goog.scope is that the compiler will *guarantee* * the anonymous function will be inlined, even if it can't prove * that it's semantically correct to do so. For example, consider this case: * *
 * goog.scope(function() {
 *   goog.getBar = function () { return alias; };
 *   ...
 *   var alias = foo.bar;
 * })
 * 
* *

In theory, the compiler can't inline 'alias' unless it can prove that * goog.getBar is called only after 'alias' is defined. In practice, the * compiler will inline 'alias' anyway, at the risk of 'fixing' bad code. * * @author [email protected] (Robby Walker) */ class ScopedAliases implements HotSwapCompilerPass { /** Name used to denote an scoped function block used for aliasing. */ static final String SCOPING_METHOD_NAME = "goog.scope"; private final AbstractCompiler compiler; private final PreprocessorSymbolTable preprocessorSymbolTable; private final AliasTransformationHandler transformationHandler; // Errors static final DiagnosticType GOOG_SCOPE_MUST_BE_ALONE = DiagnosticType.error( "JSC_GOOG_SCOPE_MUST_BE_ALONE", "The call to goog.scope must be alone in a single statement."); static final DiagnosticType GOOG_SCOPE_MUST_BE_IN_GLOBAL_SCOPE = DiagnosticType.error( "JSC_GOOG_SCOPE_MUST_BE_IN_GLOBAL_SCOPE", "The call to goog.scope must be in the global scope."); static final DiagnosticType GOOG_SCOPE_HAS_BAD_PARAMETERS = DiagnosticType.error( "JSC_GOOG_SCOPE_HAS_BAD_PARAMETERS", "The call to goog.scope must take only a single parameter. It must" + " be an anonymous function that itself takes no parameters."); static final DiagnosticType GOOG_SCOPE_REFERENCES_THIS = DiagnosticType.error( "JSC_GOOG_SCOPE_REFERENCES_THIS", "The body of a goog.scope function cannot reference 'this'."); static final DiagnosticType GOOG_SCOPE_USES_RETURN = DiagnosticType.error( "JSC_GOOG_SCOPE_USES_RETURN", "The body of a goog.scope function cannot use 'return'."); static final DiagnosticType GOOG_SCOPE_USES_THROW = DiagnosticType.error( "JSC_GOOG_SCOPE_USES_THROW", "The body of a goog.scope function cannot use 'throw'."); static final DiagnosticType GOOG_SCOPE_ALIAS_REDEFINED = DiagnosticType.error( "JSC_GOOG_SCOPE_ALIAS_REDEFINED", "The alias {0} is assigned a value more than once."); static final DiagnosticType GOOG_SCOPE_ALIAS_CYCLE = DiagnosticType.error( "JSC_GOOG_SCOPE_ALIAS_CYCLE", "The aliases {0} has a cycle."); static final DiagnosticType GOOG_SCOPE_NON_ALIAS_LOCAL = DiagnosticType.error( "JSC_GOOG_SCOPE_NON_ALIAS_LOCAL", "The local variable {0} is in a goog.scope and is not an alias."); static final DiagnosticType GOOG_SCOPE_INVALID_VARIABLE = DiagnosticType.error( "JSC_GOOG_SCOPE_INVALID_VARIABLE", "The variable {0} cannot be declared in this scope"); private Multiset scopedAliasNames = HashMultiset.create(); ScopedAliases(AbstractCompiler compiler, @Nullable PreprocessorSymbolTable preprocessorSymbolTable, AliasTransformationHandler transformationHandler) { this.compiler = compiler; this.preprocessorSymbolTable = preprocessorSymbolTable; this.transformationHandler = transformationHandler; } @Override public void process(Node externs, Node root) { hotSwapScript(root, null); } @Override public void hotSwapScript(Node root, Node originalRoot) { Traversal traversal = new Traversal(); NodeTraversal.traverseEs6(compiler, root, traversal); if (!traversal.hasErrors()) { // Apply the aliases. List aliasWorkQueue = new ArrayList<>(traversal.getAliasUsages()); while (!aliasWorkQueue.isEmpty()) { List newQueue = new ArrayList<>(); for (AliasUsage aliasUsage : aliasWorkQueue) { if (aliasUsage.referencesOtherAlias()) { newQueue.add(aliasUsage); } else { aliasUsage.applyAlias(compiler); } } // Prevent an infinite loop. if (newQueue.size() == aliasWorkQueue.size()) { Var cycleVar = newQueue.get(0).aliasVar; compiler.report(JSError.make( cycleVar.getNode(), GOOG_SCOPE_ALIAS_CYCLE, cycleVar.getName())); break; } else { aliasWorkQueue = newQueue; } } // Remove the alias definitions. for (Node aliasDefinition : traversal.getAliasDefinitionsInOrder()) { compiler.reportChangeToEnclosingScope(aliasDefinition); if (NodeUtil.isNameDeclaration(aliasDefinition.getParent()) && aliasDefinition.getParent().hasOneChild()) { aliasDefinition.getParent().detach(); } else { aliasDefinition.detach(); } } // Collapse the scopes. for (Node scopeCall : traversal.getScopeCalls()) { Node expressionWithScopeCall = scopeCall.getParent(); Node scopeClosureBlock = scopeCall.getLastChild().getLastChild(); scopeClosureBlock.detach(); expressionWithScopeCall.replaceWith(scopeClosureBlock); compiler.reportChangeToEnclosingScope(scopeClosureBlock); NodeUtil.tryMergeBlock(scopeClosureBlock); } } } private abstract static class AliasUsage { final Var aliasVar; final Node aliasReference; AliasUsage(Var aliasVar, Node aliasReference) { this.aliasVar = aliasVar; this.aliasReference = aliasReference; } /** Checks to see if this references another alias. */ public boolean referencesOtherAlias() { Node aliasDefinition = aliasVar.getInitialValue(); Node root = NodeUtil.getRootOfQualifiedName(aliasDefinition); Var otherAliasVar = aliasVar.getScope().getOwnSlot(root.getString()); return otherAliasVar != null; } public abstract void applyAlias(AbstractCompiler compiler); } private static class AliasedNode extends AliasUsage { AliasedNode(Var aliasVar, Node aliasReference) { super(aliasVar, aliasReference); } @Override public void applyAlias(AbstractCompiler compiler) { Node aliasDefinition = aliasVar.getInitialValue(); Node replacement = aliasDefinition.cloneTree(); replacement.useSourceInfoFromForTree(aliasReference); if (aliasReference.isStringKey()) { Preconditions.checkState(!aliasReference.hasChildren()); aliasReference.addChildToFront(replacement); } else { aliasReference.replaceWith(replacement); } compiler.reportChangeToEnclosingScope(replacement); } } private static class AliasedTypeNode extends AliasUsage { AliasedTypeNode(Var aliasVar, Node aliasReference) { super(aliasVar, aliasReference); } @Override public void applyAlias(AbstractCompiler compiler) { Node aliasDefinition = aliasVar.getInitialValue(); String aliasName = aliasVar.getName(); String typeName = aliasReference.getString(); if (typeName.startsWith("$jscomp.scope.")) { // Already visited. return; } String aliasExpanded = Preconditions.checkNotNull(aliasDefinition.getQualifiedName()); Preconditions.checkState(typeName.startsWith(aliasName), "%s must start with %s", typeName, aliasName); String replacement = aliasExpanded + typeName.substring(aliasName.length()); aliasReference.setString(replacement); } } private class Traversal extends NodeTraversal.AbstractPostOrderCallback implements NodeTraversal.ScopedCallback { // The job of this class is to collect these three data sets. // The order of this list determines the order that aliases are applied. private final List aliasDefinitionsInOrder = new ArrayList<>(); private final List scopeCalls = new ArrayList<>(); private final List aliasUsages = new ArrayList<>(); // This map is temporary and cleared for each scope. private final Map aliases = new HashMap<>(); // Also temporary and cleared for each scope. private final Set injectedDecls = new HashSet<>(); // Suppose you create an alias. // var x = goog.x; // As a side-effect, this means you can shadow the namespace 'goog' // in inner scopes. When we inline the namespaces, we have to rename // these shadows. // // Fortunately, we already have a name uniquifier that runs during tree // normalization (before optimizations). We run it here on a limited // set of variables, but only as a last resort (because this will screw // up warning messages downstream). private final Set forbiddenLocals = new HashSet<>( ImmutableSet.of("$jscomp")); private boolean hasNamespaceShadows = false; private boolean hasErrors = false; private AliasTransformation transformation = null; // The body of the function that is passed to goog.scope. // Set when the traversal enters the body, and set back to null when it exits. private Node scopeFunctionBody = null; Collection getAliasDefinitionsInOrder() { return aliasDefinitionsInOrder; } private List getAliasUsages() { return aliasUsages; } List getScopeCalls() { return scopeCalls; } boolean hasErrors() { return hasErrors; } /** * Returns true if this NodeTraversal is currently within a goog.scope function body */ private boolean inGoogScopeBody() { return scopeFunctionBody != null; } /** * Returns true if n is the goog.scope function body */ private boolean isGoogScopeFunctionBody(Node n) { return inGoogScopeBody() && n == scopeFunctionBody; } private boolean isCallToScopeMethod(Node n) { return n.isCall() && n.getFirstChild().matchesQualifiedName(SCOPING_METHOD_NAME); } /** * @param scopeRoot the Node which is the root of the current scope * @return the goog.scope() CALL node containing the scopeRoot, or null if scopeRoot is not * in a goog.scope() call. */ private Node findScopeMethodCall(Node scopeRoot) { Node n = scopeRoot.getGrandparent(); if (isCallToScopeMethod(n)) { return n; } return null; } @Override public void enterScope(NodeTraversal t) { if (t.inGlobalHoistScope()) { return; } if (inGoogScopeBody()) { Scope hoistedScope = t.getClosestHoistScope(); if (isGoogScopeFunctionBody(hoistedScope.getRootNode())) { findAliases(t, hoistedScope); } } Node scopeMethodCall = findScopeMethodCall(t.getScopeRoot()); if (scopeMethodCall != null) { transformation = transformationHandler.logAliasTransformation( scopeMethodCall.getSourceFileName(), getSourceRegion(scopeMethodCall)); findAliases(t, t.getScope()); scopeFunctionBody = scopeMethodCall.getLastChild().getLastChild(); } } @Override public void exitScope(NodeTraversal t) { if (isGoogScopeFunctionBody(t.getScopeRoot())) { scopeFunctionBody = null; renameNamespaceShadows(t); injectedDecls.clear(); aliases.clear(); forbiddenLocals.clear(); transformation = null; hasNamespaceShadows = false; } else if (inGoogScopeBody()) { findNamespaceShadows(t); reportInvalidVariables(t); } } private void reportInvalidVariables(NodeTraversal t) { Node scopeRoot = t.getScopeRoot(); Node enclosingFunctionBody = t.getEnclosingFunction().getLastChild(); if (isGoogScopeFunctionBody(enclosingFunctionBody) && scopeRoot.isNormalBlock() && !scopeRoot.getParent().isFunction()) { for (Var v : t.getScope().getVarIterable()) { Node parent = v.getNameNode().getParent(); if (NodeUtil.isFunctionDeclaration(parent)) { // Disallow block-scoped function declarations that leak into the goog.scope // function body. Technically they shouldn't leak in ES6 but the browsers don't agree // on that yet. report(t, v.getNode(), GOOG_SCOPE_INVALID_VARIABLE, v.getName()); } } } } private SourcePosition getSourceRegion(Node n) { Node testNode = n; Node next = null; for (; next != null || testNode.isScript();) { next = testNode.getNext(); testNode = testNode.getParent(); } int endLine = next == null ? Integer.MAX_VALUE : next.getLineno(); int endChar = next == null ? Integer.MAX_VALUE : next.getCharno(); SourcePosition pos = new SourcePosition() {}; pos.setPositionInformation( n.getLineno(), n.getCharno(), endLine, endChar); return pos; } private void report(NodeTraversal t, Node n, DiagnosticType error, String... arguments) { compiler.report(t.makeError(n, error, arguments)); hasErrors = true; } private void findAliases(NodeTraversal t, Scope scope) { for (Var v : scope.getVarIterable()) { Node n = v.getNode(); Node parent = n.getParent(); // We use isBlock to avoid variables declared in loop headers. boolean isVar = NodeUtil.isNameDeclaration(parent) && parent.getParent().isNormalBlock(); boolean isFunctionDecl = NodeUtil.isFunctionDeclaration(parent); if (isVar && n.getFirstChild() != null && n.getFirstChild().isQualifiedName()) { recordAlias(v); } else if (v.isBleedingFunction()) { // Bleeding functions already get a BAD_PARAMETERS error, so just // do nothing. } else if (parent.isParamList()) { // Parameters of the scope function also get a BAD_PARAMETERS // error. } else if (isVar || isFunctionDecl || NodeUtil.isClassDeclaration(parent)) { boolean isHoisted = NodeUtil.isHoistedFunctionDeclaration(parent); Node grandparent = parent.getParent(); Node value = v.getInitialValue(); Node varNode = null; // Pull out inline type declaration if present. if (n.getJSDocInfo() != null) { JSDocInfoBuilder builder = JSDocInfoBuilder.maybeCopyFrom(parent.getJSDocInfo()); if (isFunctionDecl) { // Fix inline return type. builder.recordReturnType(n.getJSDocInfo().getType()); } else { builder.recordType(n.getJSDocInfo().getType()); } parent.setJSDocInfo(builder.build()); n.setJSDocInfo(null); } // Grab the docinfo before we do any AST manipulation. JSDocInfo varDocInfo = v.getJSDocInfo(); String name = n.getString(); int nameCount = scopedAliasNames.count(name); scopedAliasNames.add(name); String globalName = "$jscomp.scope." + name + (nameCount == 0 ? "" : ("$jscomp$" + nameCount)); Node lastInjectedNode = compiler.ensureLibraryInjected("base", false); if (lastInjectedNode != null) { compiler.reportChangeToEnclosingScope(lastInjectedNode); } // First, we need to free up the function expression (EXPR) // to be used in another expression. if (isFunctionDecl || NodeUtil.isClassDeclaration(parent)) { // Replace "function NAME() { ... }" with "var NAME;". // Replace "class NAME { ... }" with "var NAME;". // We can't keep the local name on the function expression, // because IE is buggy and will leak the name into the global // scope. This is covered in more detail here: // http://wiki.ecmascript.org/lib/exe/fetch.php?id=resources:resources&cache=cache&media=resources:jscriptdeviationsfromes3.pdf // // This will only cause problems if this is a hoisted, recursive // function, and the programmer is using the hoisting. Node newName; if (isFunctionDecl) { newName = IR.name(""); } else { newName = IR.empty(); } newName.useSourceInfoFrom(n); value.replaceChild(n, newName); compiler.reportChangeToEnclosingScope(newName); varNode = IR.var(n).useSourceInfoFrom(n); grandparent.replaceChild(parent, varNode); } else { if (value != null) { // If this is a VAR, we can just detach the expression and // the tree will still be valid. value.detach(); } varNode = parent; } // Add $jscomp.scope.name = EXPR; // Make sure we copy over all the jsdoc and debug info. if (value != null || varDocInfo != null) { Node newDecl = NodeUtil.newQNameDeclaration( compiler, globalName, value, varDocInfo) .useSourceInfoIfMissingFromForTree(n); newDecl.getFirstFirstChild().useSourceInfoFrom(n); newDecl.getFirstFirstChild().setOriginalName(name); if (isHoisted) { grandparent.addChildToFront(newDecl); } else { grandparent.addChildBefore(newDecl, varNode); } compiler.reportChangeToEnclosingScope(newDecl); injectedDecls.add(newDecl.getFirstChild()); } // Rewrite "var name = EXPR;" to "var name = $jscomp.scope.name;" v.getNameNode().addChildToFront( NodeUtil.newQName( compiler, globalName, n, name)); recordAlias(v); } else { // Do not other kinds of local symbols, like catch params. report(t, n, GOOG_SCOPE_NON_ALIAS_LOCAL, n.getString()); } } } private void recordAlias(Var aliasVar) { String name = aliasVar.getName(); aliases.put(name, aliasVar); String qualifiedName = aliasVar.getInitialValue().getQualifiedName(); transformation.addAlias(name, qualifiedName); int rootIndex = qualifiedName.indexOf('.'); if (rootIndex != -1) { String qNameRoot = qualifiedName.substring(0, rootIndex); if (!aliases.containsKey(qNameRoot)) { forbiddenLocals.add(qNameRoot); } } } /** Find out if there are any local shadows of namespaces. */ private void findNamespaceShadows(NodeTraversal t) { if (hasNamespaceShadows) { return; } Scope scope = t.getScope(); for (Var v : scope.getVarIterable()) { if (forbiddenLocals.contains(v.getName())) { hasNamespaceShadows = true; return; } } } /** * Rename any local shadows of namespaces. * This should be a very rare occurrence, so only do this traversal * if we know that we need it. */ private void renameNamespaceShadows(NodeTraversal t) { if (hasNamespaceShadows) { MakeDeclaredNamesUnique.Renamer renamer = new MakeDeclaredNamesUnique.WhitelistedRenamer( new MakeDeclaredNamesUnique.ContextualRenamer(), forbiddenLocals); for (String s : forbiddenLocals) { renamer.addDeclaredName(s, false); } MakeDeclaredNamesUnique uniquifier = new MakeDeclaredNamesUnique(renamer); Node parent = t.getScopeRoot().getParent(); NodeTraversal.traverseEs6(compiler, parent, uniquifier); } } private void renameBleedingFunctionName(Node fnName) { MakeDeclaredNamesUnique.Renamer renamer = new MakeDeclaredNamesUnique.WhitelistedRenamer( new MakeDeclaredNamesUnique.ContextualRenamer(), ImmutableSet.of(fnName.getString())); renamer.addDeclaredName(fnName.getString(), false); MakeDeclaredNamesUnique uniquifier = new MakeDeclaredNamesUnique(renamer); NodeTraversal.traverseEs6(compiler, fnName.getParent().getParent(), uniquifier); } private void validateScopeCall(NodeTraversal t, Node n, Node parent) { if (preprocessorSymbolTable != null) { preprocessorSymbolTable.addReference(n.getFirstChild()); } if (!parent.isExprResult()) { report(t, n, GOOG_SCOPE_MUST_BE_ALONE); } if (t.getEnclosingFunction() != null) { report(t, n, GOOG_SCOPE_MUST_BE_IN_GLOBAL_SCOPE); } if (n.getChildCount() != 2) { // The goog.scope call should have exactly 1 parameter. The first // child is the "goog.scope" and the second should be the parameter. report(t, n, GOOG_SCOPE_HAS_BAD_PARAMETERS); } else { Node anonymousFnNode = n.getSecondChild(); if (!anonymousFnNode.isFunction() || NodeUtil.getName(anonymousFnNode) != null || NodeUtil.getFunctionParameters(anonymousFnNode).hasChildren()) { report(t, anonymousFnNode, GOOG_SCOPE_HAS_BAD_PARAMETERS); } else { scopeCalls.add(n); } } } @Override public void visit(NodeTraversal t, Node n, Node parent) { if (isCallToScopeMethod(n)) { validateScopeCall(t, n, n.getParent()); } if (!inGoogScopeBody()) { return; } Token type = n.getToken(); boolean isObjLitShorthand = type == Token.STRING_KEY && !n.hasChildren(); Var aliasVar = null; if (type == Token.NAME || isObjLitShorthand) { String name = n.getString(); Var lexicalVar = t.getScope().getVar(name); if (lexicalVar != null && lexicalVar == aliases.get(name)) { aliasVar = lexicalVar; // For nodes that are referencing the aliased type, set the original name so it // can be accessed later in tools such as the CodePrinter or refactoring tools. if (compiler.getOptions().preservesDetailedSourceInfo() && n.isName()) { n.setOriginalName(name); } } } if (isGoogScopeFunctionBody(t.getEnclosingFunction().getLastChild())) { if (aliasVar != null && !isObjLitShorthand && NodeUtil.isLValue(n)) { if (aliasVar.getNode() == n) { aliasDefinitionsInOrder.add(n); // Return early, to ensure that we don't record a definition // twice. return; } else { report(t, n, GOOG_SCOPE_ALIAS_REDEFINED, n.getString()); } } if (type == Token.RETURN) { report(t, n, GOOG_SCOPE_USES_RETURN); } else if (type == Token.THIS) { report(t, n, GOOG_SCOPE_REFERENCES_THIS); } else if (type == Token.THROW) { report(t, n, GOOG_SCOPE_USES_THROW); } } // If this is a bleeding function expression, like // var x = function y() { ... } // then old versions of IE declare "y" in the current scope. We don't // want the scope unboxing to add "y" to the global scope, so we // need to rename it. // // TODO(moz): Remove this once we stop supporting IE8. if (NodeUtil.isBleedingFunctionName(n)) { renameBleedingFunctionName(n); } // Check if this name points to an alias. if (aliasVar != null) { // Note, to support the transitive case, it's important we don't // clone aliasedNode here. For example, // var g = goog; var d = g.dom; d.createElement('DIV'); // The node in aliasedNode (which is "g") will be replaced in the // changes pass above with "goog". If we cloned here, we'd end up // with g.dom.createElement('DIV'). aliasUsages.add(new AliasedNode(aliasVar, n)); } // When we inject declarations, we duplicate jsdoc. Make sure // we only process that jsdoc once. JSDocInfo info = n.getJSDocInfo(); if (info != null && !injectedDecls.contains(n)) { for (Node node : info.getTypeNodes()) { fixTypeNode(node); } } } private void fixTypeNode(Node typeNode) { if (typeNode.isString()) { String name = typeNode.getString(); int endIndex = name.indexOf('.'); if (endIndex == -1) { endIndex = name.length(); } String baseName = name.substring(0, endIndex); Var aliasVar = aliases.get(baseName); if (aliasVar != null) { aliasUsages.add(new AliasedTypeNode(aliasVar, typeNode)); } // For nodes that are referencing the aliased type, set the original name so it // can be accessed later in tools such as the CodePrinter or refactoring tools. if (compiler.getOptions().preservesDetailedSourceInfo()) { typeNode.setOriginalName(name); } } for (Node child = typeNode.getFirstChild(); child != null; child = child.getNext()) { fixTypeNode(child); } } } }





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