com.google.javascript.jscomp.MoveFunctionDeclarations Maven / Gradle / Ivy
/*
* 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.collect.ArrayListMultimap;
import com.google.common.collect.ListMultimap;
import com.google.common.collect.Lists;
import com.google.common.collect.Multimaps;
import com.google.javascript.jscomp.NodeTraversal.Callback;
import com.google.javascript.rhino.IR;
import com.google.javascript.rhino.Node;
import java.util.List;
import java.util.Map.Entry;
/**
* Moves top-level function declarations to the top of the enclosing JSModule.
*
* Enable this pass if a try catch block wraps the output after compilation, and the output runs
* on Firefox because function declarations are only defined when reached inside a try catch block
* on older versions of Firefox.
*
*
On Firefox versions <= 45, this code works:
*
*
var g = f; function f() {}
*
*
but this code does not work:
*
*
try { var g = f; function f() {} } catch(e) {}
*
*
NOTE(lharker): As of Firefox version 46 the above code works. Projects not supporting older
* versions of Firefox shouldn't need this pass.
*
*
RescopeGlobalSymbols still depends on this pass running first to preserve function hoisting
* semantics.
*
*
NOTE(dimvar): This pass is safe to turn on by default and delete the associated compiler
* option. However, we don't do that because the pass is only useful for code wrapped in a
* try/catch, and otherwise it makes debugging harder because it moves code around.
*
*/
class MoveFunctionDeclarations implements Callback, CompilerPass {
private final AbstractCompiler compiler;
private final ListMultimap functions;
MoveFunctionDeclarations(AbstractCompiler compiler) {
this.compiler = compiler;
functions = ArrayListMultimap.create();
}
@Override
public void process(Node externs, Node root) {
NodeTraversal.traverse(compiler, root, this);
for (Entry> entry : Multimaps.asMap(functions).entrySet()) {
Node addingRoot = compiler.getNodeForCodeInsertion(entry.getKey());
List fnNodes = Lists.reverse(entry.getValue());
if (!fnNodes.isEmpty()) {
for (Node n : fnNodes) {
Node nameNode = n.getFirstChild();
String name = nameNode.getString();
nameNode.setString("");
addingRoot.addChildToFront(
IR.var(IR.name(name), n).useSourceInfoIfMissingFromForTree(n));
compiler.reportChangeToEnclosingScope(nameNode);
}
compiler.reportChangeToEnclosingScope(addingRoot);
}
}
}
@Override
public boolean shouldTraverse(NodeTraversal t, Node n, Node parent) {
Node grandparent = n.getAncestor(2);
return grandparent == null || !grandparent.isScript();
}
@Override
public void visit(NodeTraversal t, Node n, Node parent) {
if (parent == null || !parent.isScript()) {
return;
}
if (NodeUtil.isFunctionDeclaration(n)) {
parent.removeChild(n);
compiler.reportChangeToEnclosingScope(parent);
functions.put(t.getModule(), n);
}
}
}