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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 static com.google.common.base.Preconditions.checkState;

import com.google.javascript.rhino.Node;

/**
 * Annotates nodes with information from their original input file
 * before the compiler performs work that changes this information (such
 * as its original location, its original name, etc).
 *
 * Information saved:
 *
 * - Annotates all NAME nodes with an ORIGINALNAME_PROP indicating its original
 *   name.
 *
 * - Annotates all string GET_PROP nodes with an ORIGINALNAME_PROP.
 *
 * - Annotates all OBJECT_LITERAL unquoted string key nodes with an
 *   ORIGINALNAME_PROP.
 *
 * - Annotates all FUNCTION nodes with an ORIGINALNAME_PROP indicating its
 *   nearest original name.
 *
 */
class SourceInformationAnnotator extends
  NodeTraversal.AbstractPostOrderCallback {
  private final String sourceFile;
  private final boolean checkAnnotated;

  public SourceInformationAnnotator(
      String sourceFile, boolean checkAnnotated) {
    this.sourceFile = sourceFile;
    this.checkAnnotated = checkAnnotated;
  }

  @Override
  public void visit(NodeTraversal t, Node n, Node parent) {
    // Verify the source file is annotated.
    if (checkAnnotated && sourceFile != null) {
      checkState(sourceFile.equals(n.getSourceFileName()));
    }

    // Annotate the original name.
    switch (n.getToken()) {
      case GETPROP:
        Node propNode = n.getLastChild();
        setOriginalName(n, propNode.getString());
        break;

      case FUNCTION:
        String functionName = NodeUtil.getNearestFunctionName(n);
        if (functionName != null) {
          setOriginalName(n, functionName);
        }
        break;

      case NAME:
        setOriginalName(n, n.getString());
        break;

      case OBJECTLIT:
        for (Node key = n.getFirstChild(); key != null; key = key.getNext()) {
          // Set the original name for unquoted string properties.
          if (!key.isComputedProp() && !key.isQuotedString() && !key.isSpread()) {
            setOriginalName(key, key.getString());
          }
        }
        break;
      default:
        break;
    }
  }

  static void setOriginalName(Node n, String name) {
    if (!name.isEmpty() && n.getOriginalName() == null) {
      n.setOriginalName(name);
    }
  }
}