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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 2019 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.parsing;

import static com.google.common.base.Preconditions.checkNotNull;

import com.google.javascript.rhino.Node;
import java.util.function.Consumer;

/** Utility functions for parsing that don't depend on the compiler. */
public final class ParsingUtil {
  // Utility class; do not instantiate.
  private ParsingUtil() {}

  /** Calls {@code cb} with all NAMEs declared in a PARAM_LIST or destructuring pattern. */
  public static void getParamOrPatternNames(Node n, Consumer cb) {
    checkNotNull(n);
    switch (n.getToken()) {
      case EMPTY: // let [,] = ...
      case GETELEM: // [someArray[1]] = ...
      case GETPROP: // [someObj.someProp] = ...
        // An empty node or assigned to an existing value means nothings here and we can't recurse
        // further.
        break;

      case NAME: // let [someName] = ...
        // A name node generally means we found an assignment happening.
        cb.accept(n);
        break;

      case ITER_REST: // let [...name] = ...
      case OBJECT_REST: // let {...name} = ...
      case STRING_KEY: // let {name} = ...
      case DEFAULT_VALUE: // let {name = 10} = ...
        // For these node types there is a name node as the first child.
        getParamOrPatternNames(n.getFirstChild(), cb);
        break;

      case COMPUTED_PROP: // let {[someProp]: name} = ...
        // For this node types there is a name node as the second child.
        getParamOrPatternNames(n.getSecondChild(), cb);
        break;

      case OBJECT_PATTERN: // let {} = ...
      case ARRAY_PATTERN: // let [] = ...
      case PARAM_LIST: // function fn() ...
        // Each item in the destructuring pattern is scanned for assignments. Although PARAM_LIST
        // isn't technically a pattern, we know how to handle it anyway.
        for (Node c = n.getFirstChild(); c != null; c = c.getNext()) {
          getParamOrPatternNames(c, cb);
        }
        break;

      default:
        throw new IllegalStateException("Unexpected parameter structure");
    }
  }
}