com.google.javascript.jscomp.Es6SyntacticScopeCreator Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of closure-compiler Show documentation
Show all versions of closure-compiler Show documentation
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 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 com.google.common.base.Preconditions;
import com.google.javascript.jscomp.SyntacticScopeCreator.DefaultRedeclarationHandler;
import com.google.javascript.jscomp.SyntacticScopeCreator.RedeclarationHandler;
import com.google.javascript.rhino.InputId;
import com.google.javascript.rhino.Node;
/**
* The syntactic scope creator scans the parse tree to create a Scope object
* containing all the variable declarations in that scope. This class adds support
* for block-level scopes introduced in ECMAScript 6.
*
* This implementation is not thread-safe.
*
* @author [email protected] (Michael Zhou)
*/
class Es6SyntacticScopeCreator implements ScopeCreator {
private final AbstractCompiler compiler;
private Scope scope;
private InputId inputId;
private final RedeclarationHandler redeclarationHandler;
// The arguments variable is special, in that it's declared for every function,
// but not explicitly declared.
private static final String ARGUMENTS = "arguments";
Es6SyntacticScopeCreator(AbstractCompiler compiler) {
this.compiler = compiler;
this.redeclarationHandler = new DefaultRedeclarationHandler();
}
Es6SyntacticScopeCreator(
AbstractCompiler compiler, RedeclarationHandler redeclarationHandler) {
this.compiler = compiler;
this.redeclarationHandler = redeclarationHandler;
}
@Override
public Scope createScope(Node n, Scope parent) {
inputId = null;
if (parent == null) {
scope = Scope.createGlobalScope(n);
} else {
scope = new Scope(parent, n);
}
scanRoot(n);
inputId = null;
Scope returnedScope = scope;
scope = null;
return returnedScope;
}
private void scanRoot(Node n) {
if (n.isFunction()) {
if (inputId == null) {
inputId = NodeUtil.getInputId(n);
// TODO(johnlenz): inputId maybe null if the FUNCTION node is detached
// from the AST.
// Is it meaningful to build a scope for detached FUNCTION node?
}
final Node fnNameNode = n.getFirstChild();
final Node args = fnNameNode.getNext();
// Bleed the function name into the scope, if it hasn't
// been declared in the outer scope.
String fnName = fnNameNode.getString();
if (!fnName.isEmpty() && NodeUtil.isFunctionExpression(n)) {
declareVar(fnNameNode);
}
// Args: Declare function variables
checkState(args.isParamList());
declareLHS(args);
// Since we create a separate scope for body, stop scanning here
} else if (n.isClass()) {
if (scope.getParent() != null) {
inputId = NodeUtil.getInputId(n);
}
final Node classNameNode = n.getFirstChild();
// Bleed the class name into the scope, if it hasn't
// been declared in the outer scope.
if (!classNameNode.isEmpty()) {
if (NodeUtil.isClassExpression(n)) {
declareVar(classNameNode);
}
}
} else if (n.isBlock()
|| NodeUtil.isAnyFor(n)
|| n.isSwitch()
|| n.isModuleBody()) {
if (scope.getParent() != null) {
inputId = NodeUtil.getInputId(n);
}
boolean scanInnerBlocks =
n.isRoot() || NodeUtil.isFunctionBlock(n) || n.isModuleBody();
scanVars(n, scanInnerBlocks, true);
} else {
// n is the global SCRIPT node
checkState(scope.getParent() == null);
scanVars(n, true, true);
}
}
private void declareLHS(Node n) {
for (Node lhs : NodeUtil.getLhsNodesOfDeclaration(n)) {
declareVar(lhs);
}
}
/**
* Scans and gather variables declarations under a Node
*
* @param n The node
* @param scanInnerBlockScopes Whether the inner block scopes should be scanned for "var"s
* @param firstScan Whether it is the first time a scan is performed from the current scope
*/
private void scanVars(Node n, boolean scanInnerBlockScopes, boolean firstScan) {
switch (n.getToken()) {
case VAR:
if (scope.getClosestHoistScope() == scope) {
declareLHS(n);
}
return;
case LET:
case CONST:
// Only declare when scope is the current lexical scope
if (!isNodeAtCurrentLexicalScope(n)) {
return;
}
declareLHS(n);
return;
case FUNCTION:
if (NodeUtil.isFunctionExpression(n) || !isNodeAtCurrentLexicalScope(n)) {
return;
}
String fnName = n.getFirstChild().getString();
if (fnName.isEmpty()) {
// This is invalid, but allow it so the checks can catch it.
return;
}
declareVar(n.getFirstChild());
return; // should not examine function's children
case CLASS:
if (NodeUtil.isClassExpression(n) || !isNodeAtCurrentLexicalScope(n)) {
return;
}
String className = n.getFirstChild().getString();
if (className.isEmpty()) {
// This is invalid, but allow it so the checks can catch it.
return;
}
declareVar(n.getFirstChild());
return; // should not examine class's children
case CATCH:
checkState(n.hasTwoChildren(), n);
// the first child is the catch var and the second child
// is the code block
if (isNodeAtCurrentLexicalScope(n)) {
declareLHS(n);
}
// A new scope is not created for this BLOCK because there is a scope
// created for the BLOCK above the CATCH
final Node block = n.getSecondChild();
scanVars(block, scanInnerBlockScopes, false);
return; // only one child to scan
case SCRIPT:
inputId = n.getInputId();
Preconditions.checkNotNull(inputId);
break;
default:
break;
}
if (!scanInnerBlockScopes && !firstScan && NodeUtil.createsBlockScope(n)) {
return;
}
// Variables can only occur in statement-level nodes, so
// we only need to traverse children in a couple special cases.
if (NodeUtil.isControlStructure(n) || NodeUtil.isStatementBlock(n)) {
for (Node child = n.getFirstChild();
child != null;) {
Node next = child.getNext();
scanVars(child, scanInnerBlockScopes, false);
child = next;
}
}
}
/**
* Declares a variable.
*
* @param s The scope to declare the variable in.
* @param n The node corresponding to the variable name.
*/
private void declareVar(Node n) {
checkState(n.isName() || n.isStringKey(),
"Invalid node for declareVar: %s", n);
String name = n.getString();
// Because of how we scan the variables, it is possible to encounter
// the same var declared name node twice. Bail out in this case.
// TODO(johnlenz): hash lookups are not free and
// building scopes are already expensive
// restructure the scope building to avoid this check.
Var v = scope.getOwnSlot(name);
if (v != null && v.getNode() == n) {
return;
}
CompilerInput input = compiler.getInput(inputId);
if (v != null
|| isShadowingDisallowed(name)
|| (scope.isLocal() && name.equals(ARGUMENTS))) {
redeclarationHandler.onRedeclaration(scope, name, n, input);
} else {
scope.declare(name, n, input);
}
}
// Function body declarations are not allowed to shadow
// function parameters.
private boolean isShadowingDisallowed(String name) {
if (scope.isFunctionBlockScope()) {
return scope.getParent().getOwnSlot(name) != null;
}
return false;
}
/**
* Determines whether the name should be declared at current lexical scope.
* Assume the parent node is a BLOCK, FOR, FOR_OF, SCRIPT, MODULE_BODY, or LABEL.
*
* @param n The declaration node to be checked
* @return whether the name should be declared at current lexical scope
*/
private boolean isNodeAtCurrentLexicalScope(Node n) {
Node parent = n.getParent();
Node grandparent = parent.getParent();
switch (parent.getToken()) {
case SCRIPT:
return true;
case BLOCK:
if (grandparent.isCase() || grandparent.isDefaultCase() || grandparent.isCatch()) {
return scope.getRootNode() == grandparent.getParent();
}
// Fall through
case FOR:
case FOR_IN:
case FOR_OF:
case MODULE_BODY:
return parent == scope.getRootNode();
case LABEL:
while (parent.isLabel()) {
if (parent.getParent() == scope.getRootNode()) {
return true;
}
parent = parent.getParent();
}
return false;
default:
throw new RuntimeException("Unsupported node parent: " + parent);
}
}
@Override
public boolean hasBlockScope() {
return true;
}
}