com.google.javascript.jscomp.MoveFunctionDeclarations.java Source code

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Here is the source code for com.google.javascript.jscomp.MoveFunctionDeclarations.java

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/*
 * 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.Lists;
import com.google.javascript.jscomp.NodeTraversal.Callback;
import com.google.javascript.rhino.Node;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;

/**
 * Moves top-level function declarations to the top.
 *
 * 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 Firefox.
 *
 * On Firefox, this code works:
 *
 * var g = f;
 * function f() {}
 *
 * but this code does not work:
 *
 * try {
 *   var g = f;
 *   function f() {}
 * } catch(e) {}
 *
 */
class MoveFunctionDeclarations implements Callback, CompilerPass {
    private final AbstractCompiler compiler;
    private final Map<JSModule, List<Node>> functions;

    MoveFunctionDeclarations(AbstractCompiler compiler) {
        this.compiler = compiler;
        functions = new HashMap<>();
    }

    @Override
    public void process(Node externs, Node root) {
        NodeTraversal.traverse(compiler, root, this);
        for (Entry<JSModule, List<Node>> entry : functions.entrySet()) {
            JSModule module = entry.getKey();
            Node addingRoot = compiler.getNodeForCodeInsertion(module);
            for (Node n : Lists.reverse(entry.getValue())) {
                addingRoot.addChildToFront(n);
            }
        }
    }

    @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.reportCodeChange();

            JSModule module = t.getModule();
            List<Node> moduleFunctions = functions.get(module);
            if (moduleFunctions == null) {
                moduleFunctions = new ArrayList<>();
                functions.put(module, moduleFunctions);
            }
            moduleFunctions.add(n);
        }
    }
}