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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 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.parsing;

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

import com.google.common.collect.ImmutableMap;
import com.google.common.collect.ImmutableSet;
import com.google.javascript.jscomp.parsing.parser.FeatureSet;
import java.util.Set;

/**
 * Configuration for the AST factory. Should be shared across AST creation
 * for all files of a compilation process.
 *
 * @author [email protected] (Nick Santos)
 */
public final class Config {

  /**
   * Level of language strictness required for the input source code.
   */
  public enum StrictMode {
    STRICT, SLOPPY;
  }

  /** JavaScript mode */
  public enum LanguageMode {

    // Note that minimumRequiredFor() relies on these being defined in order from fewest features to
    // most features, and _STRICT versions should be supplied after unspecified strictness.
    ECMASCRIPT3(FeatureSet.ES3),
    ECMASCRIPT5(FeatureSet.ES5),
    ECMASCRIPT6(FeatureSet.ES6_MODULES),
    ECMASCRIPT7(FeatureSet.ES7_MODULES),
    ECMASCRIPT8(FeatureSet.ES8_MODULES),
    TYPESCRIPT(FeatureSet.TYPESCRIPT),
    ;

    public final FeatureSet featureSet;

    LanguageMode(FeatureSet featureSet) {
      this.featureSet = featureSet;
    }

    /**
     * Returns the lowest {@link LanguageMode} that supports the specified feature.
     */
    public static LanguageMode minimumRequiredFor(FeatureSet.Feature feature) {
      // relies on the LanguageMode enums being in the right order
      for (LanguageMode mode : LanguageMode.values()) {
        if (mode.featureSet.contains(feature)) {
          return mode;
        }
      }
      throw new IllegalStateException("No input language mode supports feature: " + feature);
    }
  }

  /**
   * Whether to parse the descriptions of JsDoc comments.
   */
  public enum JsDocParsing {
    TYPES_ONLY,
    INCLUDE_DESCRIPTIONS_NO_WHITESPACE,
    INCLUDE_DESCRIPTIONS_WITH_WHITESPACE;

    boolean shouldParseDescriptions() {
      return this != TYPES_ONLY;
    }
  }
  final JsDocParsing parseJsDocDocumentation;

  /**
   * Whether to keep going after encountering a parse error.
   */
  public enum RunMode {
    STOP_AFTER_ERROR,
    KEEP_GOING,
  }
  final RunMode keepGoing;

  /**
   * Recognized JSDoc annotations, mapped from their name to their internal
   * representation.
   */
  final ImmutableMap annotationNames;

  /**
   * Recognized names in a {@code @suppress} tag.
   */
  final ImmutableSet suppressionNames;

  /**
   * Accept ECMAScript5 syntax, such as getter/setter.
   */
  final LanguageMode languageMode;

  final StrictMode strictMode;

  /**
   * Parse inline source maps (//# sourceMappingURL=data:...).
   */
  final boolean parseInlineSourceMaps;

  Config(
      Set annotationWhitelist,
      Set suppressionNames,
      LanguageMode languageMode,
      StrictMode strictMode) {
    this(
        annotationWhitelist,
        JsDocParsing.TYPES_ONLY,
        RunMode.STOP_AFTER_ERROR,
        suppressionNames,
        languageMode,
        false,
        strictMode);
  }

  Config(
      Set annotationWhitelist,
      JsDocParsing parseJsDocDocumentation,
      RunMode keepGoing,
      Set suppressionNames,
      LanguageMode languageMode,
      boolean parseInlineSourceMaps,
      StrictMode strictMode) {
    checkArgument(!(languageMode == LanguageMode.ECMASCRIPT3 && strictMode == StrictMode.STRICT));
    this.parseInlineSourceMaps = parseInlineSourceMaps;
    this.annotationNames = buildAnnotationNames(annotationWhitelist);
    this.parseJsDocDocumentation = parseJsDocDocumentation;
    this.keepGoing = keepGoing;
    this.suppressionNames = ImmutableSet.copyOf(suppressionNames);
    this.languageMode = languageMode;
    this.strictMode = strictMode;
  }

  /**
   * Create the annotation names from the user-specified
   * annotation whitelist.
   */
  private static ImmutableMap buildAnnotationNames(
      Set annotationWhitelist) {
    ImmutableMap.Builder annotationBuilder =
        ImmutableMap.builder();
    annotationBuilder.putAll(Annotation.recognizedAnnotations);
    for (String unrecognizedAnnotation : annotationWhitelist) {
      if (!unrecognizedAnnotation.isEmpty()
          && !Annotation.recognizedAnnotations.containsKey(
              unrecognizedAnnotation)) {
        annotationBuilder.put(
            unrecognizedAnnotation, Annotation.NOT_IMPLEMENTED);
      }
    }
    return annotationBuilder.build();
  }
}