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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;
import org.jspecify.nullness.Nullable;

/**
 * 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 GETPROP and OPTCHAIN_GETPROP nodes with an original name.
 *   
Annotates all OBJECT_LITERAL unquoted string key nodes with an original name.
 *   
Annotates all FUNCTION nodes with an original name indicating its nearest original name.
 * 
 */
public final class SourceInformationAnnotator extends NodeTraversal.AbstractPostOrderCallback {
  private final @Nullable String sourceFileToCheck;

  private SourceInformationAnnotator(@Nullable String sourceFileToCheck) {
    this.sourceFileToCheck = sourceFileToCheck;
  }

  /** Returns an annotator that sets the original name of nodes */
  static SourceInformationAnnotator create() {
    return new SourceInformationAnnotator(null);
  }

  /**
   * Returns an annotator that both sets original name and verifies {@link Node#getSourceFileName}
   * is accurate
   */
  static SourceInformationAnnotator createWithAnnotationChecks(String sourceFile) {
    return new SourceInformationAnnotator(sourceFile);
  }

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

    // Annotate the original name.
    if (isStringNodeRequiringOriginalName(n)) {
      setOriginalName(n, n.getString());
      return;
    }

    if (n.isFunction()) {
        String functionName = NodeUtil.getNearestFunctionName(n);
        if (functionName != null) {
          setOriginalName(n, functionName);
        }
    }
  }

  /**
   * Whether JSCompiler attempts to preserve the original string attached to this node on the AST
   * post-mangling and in source maps.
   */
  public static boolean isStringNodeRequiringOriginalName(Node node) {
    switch (node.getToken()) {
      case GETPROP:
      case OPTCHAIN_GETPROP:
      case NAME:
        return true;

      case MEMBER_FUNCTION_DEF:
      case GETTER_DEF:
      case SETTER_DEF:
      case STRING_KEY:
        return node.getParent().isObjectLit() && !node.isQuotedStringKey();

      default:
        return false;
    }
  }

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