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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.

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/*
 * Copyright 2009 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.Sets;
import com.google.javascript.jscomp.NodeTraversal.AbstractPostOrderCallback;
import com.google.javascript.rhino.Node;
import com.google.javascript.rhino.Token;

import java.util.Set;

/**
 * External references of the form: "window['xx']" indicate names that must
 * be reserved when variable renaming to avoid conflicts.
 *
 * @author [email protected] (John Lenz)
 */
class GatherRawExports extends AbstractPostOrderCallback
    implements CompilerPass {

  private final AbstractCompiler compiler;

  private static final String GLOBAL_THIS_NAME = "window";

  private final Set exportedVariables = Sets.newHashSet();

  GatherRawExports(AbstractCompiler compiler) {
    this.compiler = compiler;
  }

  @Override
  public void process(Node externs, Node root) {
    Preconditions.checkState(compiler.isNormalized());
    NodeTraversal.traverse(compiler, root, this);
  }

  @Override
  public void visit(NodeTraversal t, Node n, Node parent) {
    Node sibling = n.getNext();
    if (sibling != null
        && sibling.getType() == Token.STRING
        && NodeUtil.isGet(parent)) {
      // TODO(johnlenz): Should we warn if we see a property name that
      // hasn't been exported?
      if (isGlobalThisObject(t, n)) {
        exportedVariables.add(sibling.getString());
      }
    }
  }

  private boolean isGlobalThisObject(NodeTraversal t, Node n) {
    if (n.getType() == Token.THIS) {
      return t.inGlobalScope();
    } else if (n.getType() == Token.NAME) {
      String varName = n.getString();
      if (varName.equals(GLOBAL_THIS_NAME)) {
        return true;
      }
    }
    return false;
  }

  public Set getExportedVariableNames() {
    return exportedVariables;
  }
}




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