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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 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 com.google.javascript.jscomp.parsing.parser.FeatureSet;
import com.google.javascript.rhino.Node;

/**
 * A factory for creating JSCompiler passes based on the Options
 * injected.  Contains all meta-data about compiler passes (like
 * whether it can be run multiple times, a human-readable name for
 * logging, etc.).
 *
 * @author [email protected] (Nick Santos)
 */
public abstract class PassFactory {

  private final String name;
  private final boolean isOneTimePass;

  /**
   * @param name The name of the pass that this factory creates.
   * @param isOneTimePass If true, the pass produced by this factory can
   *     only be run once.
   */
  protected PassFactory(String name, boolean isOneTimePass) {
    this.name = name;
    this.isOneTimePass = isOneTimePass;
  }

  /**
   * @return The name of this pass.
   */
  String getName() {
    return name;
  }

  @Override
  public String toString() {
    return name;
  }

  /**
   * @return Whether the pass produced by this factory can only be run once.
   */
  boolean isOneTimePass() {
    return isOneTimePass;
  }

  /**
   * Creates a new compiler pass to be run.
   */
  protected abstract CompilerPass create(AbstractCompiler compiler);

  /**
   * The set of features that this pass understands. Passes that can handle any code (no-op passes,
   * extremely simple passes that are unlikely to be broken by new features, etc.) should return
   * FeatureSet.latest().
   */
  protected abstract FeatureSet featureSet();

  /**
   * Any factory whose CompilerPass has a corresponding hot-swap version should
   * override this.
   *
   * @param compiler The compiler that can has been used to do the full compile.
   */
  protected HotSwapCompilerPass getHotSwapPass(AbstractCompiler compiler) {
    // TODO(bashir): If in future most of PassFactory's in DefaultPassConfig
    // turns out to be DefaultPassConfig.HotSwapPassFactory, we should probably
    // change the implementation here by the one in HotSwapPassFactory.
    return null;
  }


  /**
   * Create a no-op pass that can only run once. Used to break up loops.
   */
  public static PassFactory createEmptyPass(String name) {
    return new PassFactory(name, true) {
      @Override
      protected CompilerPass create(final AbstractCompiler compiler) {
        return new CompilerPass() {
          @Override
          public void process(Node externs, Node root) {}
        };
      }

      @Override
      protected FeatureSet featureSet() {
        return FeatureSet.latest();
      }
    };
  }

  /**
   * A pass-factory that is good for {@code HotSwapCompilerPass} passes.
   * Every hotswap pass is expected to be a one-time pass.
   */
  public abstract static class HotSwapPassFactory extends PassFactory {

    HotSwapPassFactory(String name) {
      super(name, true);
    }

    @Override
    protected abstract HotSwapCompilerPass create(AbstractCompiler compiler);

    @Override
    protected HotSwapCompilerPass getHotSwapPass(AbstractCompiler compiler) {
      return this.create(compiler);
    }
  }
}