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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 2008 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.annotations.VisibleForTesting;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Sets;
import com.google.javascript.rhino.InputId;
import com.google.javascript.rhino.Node;
import com.google.javascript.rhino.StaticRef;
import com.google.javascript.rhino.StaticSourceFile;
import com.google.javascript.rhino.Token;
import java.io.Serializable;
import org.jspecify.nullness.Nullable;
/**
* Represents a single declaration or reference to a variable. Note that references can only be used
* with untyped scopes and traversals.
*/
public final class Reference implements StaticRef, Serializable {
// Favor EnumSet over ImmutableSet for performance
private static final ImmutableSet DECLARATION_PARENTS =
Sets.immutableEnumSet(
Token.VAR,
Token.LET,
Token.CONST,
Token.PARAM_LIST,
Token.FUNCTION,
Token.CLASS,
Token.CATCH);
private final Node nameNode;
private final BasicBlock basicBlock;
private final Scope scope;
private final InputId inputId;
Reference(Node nameNode, NodeTraversal t, BasicBlock basicBlock) {
this(nameNode, basicBlock, t.getScope(), t.getInput().getInputId());
}
private Reference(
Node nameNode, @Nullable BasicBlock basicBlock, @Nullable Scope scope, InputId inputId) {
this.nameNode = nameNode;
this.basicBlock = basicBlock;
this.scope = scope;
this.inputId = inputId;
}
@Override
public String toString() {
return nameNode.toString();
}
/**
* Creates a variable reference in a given script file name, used in tests.
*
* @return The created reference.
*/
@VisibleForTesting
static Reference createRefForTest(CompilerInput input) {
return new Reference(new Node(Token.NAME), null, null, input.getInputId());
}
/** Makes a copy of the current reference using a new Scope instance. */
Reference cloneWithNewScope(Scope newScope) {
return new Reference(nameNode, basicBlock, newScope, inputId);
}
@Override
public Var getSymbol() {
return scope.getVar(nameNode.getString());
}
@Override
public Node getNode() {
return nameNode;
}
public InputId getInputId() {
return inputId;
}
@Override
public StaticSourceFile getSourceFile() {
return nameNode.getStaticSourceFile();
}
boolean isDeclaration() {
return isDeclarationHelper(nameNode);
}
private static boolean isDeclarationHelper(Node node) {
Node parent = node.getParent();
// Special case for class B extends A, A is not a declaration.
if (parent.isClass() && node != parent.getFirstChild()) {
return false;
}
// This condition can be true during InlineVariables.
if (parent.getParent() == null) {
return false;
}
if (NodeUtil.isNameDeclaration(parent.getParent()) && node == parent.getSecondChild()) {
// This is the RHS of a var/let/const and thus not a declaration.
return false;
}
// Special cases for destructuring patterns.
if (parent.isDestructuringLhs()
|| parent.isDestructuringPattern()
|| parent.isRest()
|| (parent.isStringKey() && parent.getParent().isObjectPattern())
|| (parent.isComputedProp()
&& parent.getParent().isObjectPattern()
&& node == parent.getLastChild())
|| (parent.isDefaultValue() && node == parent.getFirstChild())) {
return isDeclarationHelper(parent);
}
if (parent.isImport()) {
return true;
}
if (parent.isImportSpec() && node == parent.getLastChild()) {
return true;
}
// Special case for arrow function
if (parent.isArrowFunction()) {
return node == parent.getFirstChild();
}
return DECLARATION_PARENTS.contains(parent.getToken());
}
public boolean isVarDeclaration() {
return getParent().isVar();
}
boolean isLetDeclaration() {
return getParent().isLet();
}
public boolean isConstDeclaration() {
return getParent().isConst();
}
boolean isHoistedFunction() {
return NodeUtil.isHoistedFunctionDeclaration(getParent());
}
/** Determines whether the variable is initialized at the declaration. */
public boolean isInitializingDeclaration() {
// VAR and LET are the only types of variable declarations that may not initialize
// their variables. Catch blocks, named functions, and parameters all do.
return (isDeclaration() && !getParent().isVar() && !getParent().isLet())
|| nameNode.hasChildren();
}
/**
* @return For an assignment, variable declaration, or function declaration return the assigned
* value, otherwise null.
*/
Node getAssignedValue() {
return NodeUtil.getRValueOfLValue(nameNode);
}
BasicBlock getBasicBlock() {
return basicBlock;
}
Node getParent() {
return getNode().getParent();
}
Node getGrandparent() {
return getNode().getGrandparent();
}
private static boolean isLhsOfEnhancedForExpression(Node n) {
Node parent = n.getParent();
return NodeUtil.isEnhancedFor(parent) && parent.getFirstChild() == n;
}
public boolean isSimpleAssignmentToName() {
Node parent = getParent();
return parent.isAssign() && parent.getFirstChild() == nameNode;
}
/**
* Returns whether the name node for this reference is an lvalue. TODO(tbreisacher): This method
* disagrees with NodeUtil#isLValue for "var x;" and "let x;". Consider updating it to match.
*/
public boolean isLvalue() {
Node parent = getParent();
Token parentType = parent.getToken();
switch (parentType) {
case VAR:
case LET:
case CONST:
return (nameNode.hasChildren() || isLhsOfEnhancedForExpression(nameNode));
case DEFAULT_VALUE:
return parent.getFirstChild() == nameNode;
case INC:
case DEC:
case CATCH:
case ITER_REST:
case OBJECT_REST:
case PARAM_LIST:
return true;
case FOR:
case FOR_IN:
case FOR_OF:
case FOR_AWAIT_OF:
return NodeUtil.isEnhancedFor(parent) && parent.getFirstChild() == nameNode;
case ARRAY_PATTERN:
case STRING_KEY:
case COMPUTED_PROP:
return NodeUtil.isLhsByDestructuring(nameNode);
default:
return (NodeUtil.isAssignmentOp(parent) && parent.getFirstChild() == nameNode);
}
}
Scope getScope() {
return scope;
}
}