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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 2014 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 static com.google.common.base.Strings.isNullOrEmpty;

import com.google.javascript.jscomp.parsing.parser.FeatureSet;
import com.google.javascript.jscomp.parsing.parser.util.format.SimpleFormat;

/**
 * Checks for combinations of options that are incompatible, i.e. will produce
 * incorrect code.
 *
 * This is run by Compiler#compileInternal, which is not run during unit tests.
 * The catch is that it's run after Compiler#initOptions, so if for example
 * you want to change the warningsGuard, you can't do it here.
 *
 * Also, turns off options if the provided options don't make sense together.
 *
 * @author [email protected] (Tyler Breisacher)
 */
final class CompilerOptionsPreprocessor {

  static void preprocess(CompilerOptions options) {
    if (options.checkMissingGetCssNameLevel.isOn()
        && (isNullOrEmpty(options.checkMissingGetCssNameBlacklist))) {
      throw new InvalidOptionsException(
          "Cannot check use of goog.getCssName because of empty blacklist.");
    }

    if (options.removeUnusedPrototypePropertiesInExterns
        && !options.removeUnusedPrototypeProperties) {
      throw new InvalidOptionsException(
          "remove_unused_prototype_props_in_externs requires "
          + "remove_unused_prototype_props to be turned on.");
    }

    if (options.getInlineFunctionsLevel() == CompilerOptions.Reach.NONE
        && options.maxFunctionSizeAfterInlining
            != CompilerOptions.UNLIMITED_FUN_SIZE_AFTER_INLINING) {
      throw new InvalidOptionsException(
          "max_function_size_after_inlining has no effect if inlining is disabled.");
    }

    if (options.dartPass) {
      if (!options.getOutputFeatureSet().contains(FeatureSet.ES5)) {
        throw new InvalidOptionsException("Dart requires --language_out=ES5 or higher.");
      }
      // --dart_pass does not support type-aware property renaming yet.
      options.setAmbiguateProperties(false);
      options.setDisambiguateProperties(false);
    }

    if (options.removeUnusedPrototypePropertiesInExterns
        && options.exportLocalPropertyDefinitions) {
      throw new InvalidOptionsException(
          "remove_unused_prototype_props_in_externs "
          + "and export_local_property_definitions cannot be used together.");
    }

  }

  /**
   * Exception to indicate incompatible options in the CompilerOptions.
   */
  public static class InvalidOptionsException extends RuntimeException {
    private InvalidOptionsException(String message, Object... args) {
      super(SimpleFormat.format(message, args));
    }
  }

  // Don't instantiate.
  private CompilerOptionsPreprocessor() {
  }
}