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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. This binary checks for style issues such as incorrect or missing JSDoc usage, and missing goog.require() statements. It does not do more advanced checks such as typechecking.

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/*
 * Copyright 2016 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.ImmutableList;
import com.google.javascript.jscomp.NodeTraversal.AbstractPostOrderCallback;
import com.google.javascript.rhino.Node;

/**
 * Finds the externs for the PolymerElement base class and all of its properties in the externs.
 */
final class PolymerPassFindExterns extends AbstractPostOrderCallback {

  private static final String POLYMER_ELEMENT_NAME = "PolymerElement";

  private Node polymerElementExterns;
  private ImmutableList.Builder polymerElementProps;

  PolymerPassFindExterns() {
    polymerElementProps = ImmutableList.builder();
  }

  @Override
  public void visit(NodeTraversal t, Node n, Node parent) {
    if (isPolymerElementExterns(n)) {
      polymerElementExterns = n;
    } else if (isPolymerElementPropExpr(n)) {
      polymerElementProps.add(n);
    }
  }

  /**
   * @return All properties of the {@code PolymerElement} class in externs.
   */
  ImmutableList getPolymerElementProps() {
    return polymerElementProps.build();
  }

  /**
   * @return The root {@link Node} {@code PolymerElement} class in externs.
   */
  Node getPolymerElementExterns() {
    return polymerElementExterns;
  }

  /**
   * @return Whether the node is the declaration of PolymerElement.
   */
  private static boolean isPolymerElementExterns(Node value) {
    return value != null && value.isVar()
        && value.getFirstChild().matchesQualifiedName(POLYMER_ELEMENT_NAME);
  }

  /**
   * @return Whether the node is an expression result of an assignment to a property of
   * PolymerElement.
   */
  private static boolean isPolymerElementPropExpr(Node value) {
    return value != null
        && value.isExprResult()
        && value.getFirstFirstChild() != null
        && value.getFirstFirstChild().isGetProp()
        && value.getFirstFirstChild().isQualifiedName()
        && NodeUtil.getRootOfQualifiedName(
            value.getFirstFirstChild()).matchesQualifiedName(POLYMER_ELEMENT_NAME);
  }
}