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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 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.javascript.jscomp.PassFactory.HotSwapPassFactory;

import java.util.List;

/**
 * Provides a single place to manage transpilation passes.
 */
public class TranspilationPasses {
  private TranspilationPasses() {}

  /**
   * Adds all the early ES6 transpilation passes, which go before the Dart pass.
   *
   * Includes ES6 features that are straightforward to transpile.
   * We won't handle them natively in the rest of the compiler, so we always
   * transpile them, even if the output language is also ES6.
   */
  public static void addEs6EarlyPasses(List passes) {
    passes.add(es6RewriteArrowFunction);
    passes.add(es6RenameVariablesInParamLists);
    passes.add(es6SplitVariableDeclarations);
    passes.add(es6RewriteDestructuring);
  }

  /**
   * Adds all the late ES6 transpilation passes, which go after the Dart pass.
   *
   * Includes ES6 features that are best handled natively by the compiler.
   * As we convert more passes to handle these features, we will be moving the
   * transpilation later in the compilation, and eventually only transpiling
   * when the output is lower than ES6.
   */
  public static void addEs6LatePasses(List passes) {
    passes.add(es6ConvertSuper);
    passes.add(convertEs6ToEs3);
    passes.add(rewriteBlockScopedDeclaration);
    passes.add(rewriteGenerators);
    passes.add(rewritePolyfills);
  }

  static final HotSwapPassFactory es6RewriteDestructuring =
      new HotSwapPassFactory("Es6RewriteDestructuring", true) {
        @Override
        protected HotSwapCompilerPass create(final AbstractCompiler compiler) {
          return new Es6RewriteDestructuring(compiler);
        }
      };

  static final HotSwapPassFactory es6RenameVariablesInParamLists =
      new HotSwapPassFactory("Es6RenameVariablesInParamLists", true) {
        @Override
        protected HotSwapCompilerPass create(final AbstractCompiler compiler) {
          return new Es6RenameVariablesInParamLists(compiler);
        }
      };

  static final HotSwapPassFactory es6RewriteArrowFunction =
      new HotSwapPassFactory("Es6RewriteArrowFunction", true) {
        @Override
        protected HotSwapCompilerPass create(final AbstractCompiler compiler) {
          return new Es6RewriteArrowFunction(compiler);
        }
      };

  static final HotSwapPassFactory rewritePolyfills =
      new HotSwapPassFactory("RewritePolyfills", true) {
        @Override
        protected HotSwapCompilerPass create(final AbstractCompiler compiler) {
          return new RewritePolyfills(compiler);
        }
      };

  static final HotSwapPassFactory es6SplitVariableDeclarations =
      new HotSwapPassFactory("Es6SplitVariableDeclarations", true) {
        @Override
        protected HotSwapCompilerPass create(final AbstractCompiler compiler) {
          return new Es6SplitVariableDeclarations(compiler);
        }
      };

  static final HotSwapPassFactory es6ConvertSuper =
      new HotSwapPassFactory("es6ConvertSuper", true) {
    @Override
    protected HotSwapCompilerPass create(final AbstractCompiler compiler) {
      return new Es6ConvertSuper(compiler);
    }
  };

  /**
   * Does the main ES6 to ES3 conversion.
   * There are a few other passes which run before or after this one,
   * to convert constructs which are not converted by this pass.
   */
  static final HotSwapPassFactory convertEs6ToEs3 =
      new HotSwapPassFactory("convertEs6", true) {
    @Override
    protected HotSwapCompilerPass create(final AbstractCompiler compiler) {
      return new Es6ToEs3Converter(compiler);
    }
  };

  static final HotSwapPassFactory rewriteBlockScopedDeclaration =
      new HotSwapPassFactory("Es6RewriteBlockScopedDeclaration", true) {
    @Override
    protected HotSwapCompilerPass create(final AbstractCompiler compiler) {
      return new Es6RewriteBlockScopedDeclaration(compiler);
    }
  };

  static final HotSwapPassFactory rewriteGenerators =
      new HotSwapPassFactory("rewriteGenerators", true) {
    @Override
    protected HotSwapCompilerPass create(final AbstractCompiler compiler) {
      return new Es6RewriteGenerators(compiler);
    }
  };
}