com.google.javascript.jscomp.disambiguate.ColorGraphNodeFactory Maven / Gradle / Ivy

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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 2020 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.disambiguate;

import static com.google.common.collect.ImmutableSet.toImmutableSet;

import com.google.common.collect.ImmutableSet;
import com.google.javascript.jscomp.colors.Color;
import com.google.javascript.jscomp.colors.PrimitiveColor;
import com.google.javascript.jscomp.colors.UnionColor;
import java.util.LinkedHashMap;
import javax.annotation.Nullable;

/** A factory and cache for {@link ColorGraphNode} instances. */
final class ColorGraphNodeFactory {

  private final LinkedHashMap typeIndex;

  private ColorGraphNodeFactory(LinkedHashMap initialTypeIndex) {
    this.typeIndex = initialTypeIndex;
  }

  static ColorGraphNodeFactory createFactory() {
    LinkedHashMap typeIndex = new LinkedHashMap<>();
    ColorGraphNode unknownColorNode = ColorGraphNode.create(PrimitiveColor.UNKNOWN, 0);
    typeIndex.put(PrimitiveColor.UNKNOWN, unknownColorNode);
    return new ColorGraphNodeFactory(typeIndex);
  }

  /**
   * Returns the {@link ColorGraphNode} known by this factory for {@code type}.
   *
   * For a given {@code type} and factory, this method will always return the same result. The
   * results are cached.
   */
  public ColorGraphNode createNode(@Nullable Color color) {
    Color key = this.simplifyColor(color);
    return this.typeIndex.computeIfAbsent(key, this::newColorGraphNode);
  }

  public ImmutableSet getAllKnownTypes() {
    return ImmutableSet.copyOf(this.typeIndex.values());
  }

  private ColorGraphNode newColorGraphNode(Color key) {
    int id = this.typeIndex.size();
    return ColorGraphNode.create(key, id);
  }

  // Merges different colors with the same ambiguation-behavior into one
  private Color simplifyColor(@Nullable Color type) {
    if (type == null) {
      return PrimitiveColor.UNKNOWN;
    }

    if (type.isPrimitive()) {
      return PrimitiveColor.UNKNOWN;
    } else if (type.isUnion()) {
      return simplifyUnion((UnionColor) type);
    } else {
      return type;
    }
  }

  /**
   * Removes NULL_OR_VOID then recursively simplifies the union members. may create a new
   * UnionColor.
   */
  private Color simplifyUnion(UnionColor union) {
    // Remove NULL_OR_VOID then simplify components.
    ImmutableSet colors =
        union.getAlternates().stream()
            .filter(c -> !c.equals(PrimitiveColor.NULL_OR_VOID))
            .map(this::simplifyColor)
            .collect(toImmutableSet());
    switch (colors.size()) {
      case 0:
        throw new AssertionError();
      case 1:
        return colors.iterator().next();
      default:
        return UnionColor.create(colors);
    }
  }
}