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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 2007 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.javascript.jscomp.NodeTraversal.AbstractPostOrderCallback;
import com.google.javascript.jscomp.parsing.parser.FeatureSet;
import com.google.javascript.jscomp.parsing.parser.FeatureSet.Feature;
import com.google.javascript.rhino.IR;
import com.google.javascript.rhino.Node;

/**
 * Converts property accesses from quoted string or bracket access syntax to dot or unquoted string
 * syntax, where possible. Dot syntax is more compact.
 */
class ConvertToDottedProperties extends AbstractPostOrderCallback implements CompilerPass {

  private final AbstractCompiler compiler;

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

  @Override
  public void process(Node externs, Node root) {
    NodeTraversal.traverse(compiler, root, this);
    GatherGetterAndSetterProperties.update(this.compiler, externs, root);
  }

  @Override
  public void visit(NodeTraversal t, Node n, Node parent) {
    switch (n.getToken()) {
      case COMPUTED_PROP:
      case COMPUTED_FIELD_DEF:
        Node leftElem = n.getFirstChild();
        Node rightElem = leftElem.getNext();

        // not convert property named constructor.
        // ['constructor']() and constructor() are different.
        if (leftElem.isStringLit()
            && NodeUtil.isValidPropertyName(FeatureSet.ES3, leftElem.getString())
            && !leftElem.getString().equals("constructor")) {
          leftElem.detach();
          rightElem.detach();
          Node temp;
          if (n.isComputedProp()) {
            if (rightElem.isFunction()) {
              if (n.getBooleanProp(Node.COMPUTED_PROP_GETTER)) {

                temp = IR.getterDef(leftElem.getString(), rightElem);

              } else if (n.getBooleanProp(Node.COMPUTED_PROP_SETTER)) {
                temp = IR.setterDef(leftElem.getString(), rightElem);
              } else {
                if (n.getParent().isClassMembers()) {

                  temp = IR.memberFunctionDef(leftElem.getString(), rightElem);
                  NodeUtil.addFeatureToScript(
                      t.getCurrentScript(), Feature.MEMBER_DECLARATIONS, compiler);
                } else {
                  // TODO - further optimize this code to a member function
                  temp = IR.stringKey(leftElem.getString(), rightElem);
                }
              }

            } else {
              temp = IR.stringKey(leftElem.getString(), rightElem);
            }
          } else {
            temp = IR.memberFieldDef(leftElem.getString(), rightElem);
          }

          temp.setStaticMember(n.isStaticMember());
          n.replaceWith(temp);
          compiler.reportChangeToEnclosingScope(temp);
        }
        break;
      case GETTER_DEF:
      case SETTER_DEF:
      case STRING_KEY:
        if (NodeUtil.isValidPropertyName(FeatureSet.ES3, n.getString())) {
          if (n.getBooleanProp(Node.QUOTED_PROP)) {
            n.putBooleanProp(Node.QUOTED_PROP, false);
            compiler.reportChangeToEnclosingScope(n);
          }
        }
        break;
      case OPTCHAIN_GETELEM:
      case GETELEM:
        Node left = n.getFirstChild();
        Node right = left.getNext();
        if (right.isStringLit()
            && NodeUtil.isValidPropertyName(FeatureSet.ES3, right.getString())) {
          left.detach();
          right.detach();
          Node newGetProp =
              n.isGetElem()
                  ? IR.getprop(left, right.getString())
                  : (n.isOptionalChainStart()
                      ? IR.startOptChainGetprop(left, right.getString())
                      : IR.continueOptChainGetprop(left, right.getString()));
          n.replaceWith(newGetProp);
          compiler.reportChangeToEnclosingScope(newGetProp);
        }
        break;
      default:
        break;
    }
  }
}