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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 2019 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.ImmutableMap.toImmutableMap;
import static java.util.function.Function.identity;

import com.google.common.collect.ImmutableMap;
import com.google.common.collect.ImmutableSetMultimap;
import com.google.javascript.jscomp.CheckLevel;
import com.google.javascript.jscomp.JSError;
import com.google.javascript.jscomp.PropertyRenamingDiagnostics;
import com.google.javascript.rhino.Node;
import java.util.Map;
import java.util.Objects;
import java.util.function.Consumer;

/** Applies renaming to property use sites following cluster computation. */
final class UseSiteRenamer {

  private static final String INVALIDATED_NAME_VALUE = "";

  private final ImmutableMap propsToCheckLevel;
  private final Consumer errorCb;
  private final Consumer mutationCb;

  private final ImmutableSetMultimap.Builder renamingIndex =
      ImmutableSetMultimap.builder();

  UseSiteRenamer(
      ImmutableMap propsToCheckLevel,
      Consumer errorCb,
      Consumer mutationCb) {
    this.propsToCheckLevel = propsToCheckLevel;
    this.errorCb = errorCb;
    this.mutationCb = mutationCb;
  }

  /**
   * Renames all references to {@code prop}.
   *
   * If {@code prop} is invalid or should otherwise not be renamed, the AST will not be changed.
   */
  void renameUses(PropertyClustering prop) {
    if (prop.isInvalidated()) {
      this.renamingIndex.put(prop.getName(), INVALIDATED_NAME_VALUE);

      CheckLevel level = this.propsToCheckLevel.getOrDefault(prop.getName(), CheckLevel.OFF);
      if (!level.equals(CheckLevel.OFF)) {
        this.errorCb.accept(createInvalidationError(level, prop.getName()));
      }

      return;
    }

    ImmutableMap clusterNames = createAllClusterNames(prop);

    if (clusterNames.size() <= 1) {
      /**
       * Don't bother renaming clusters with a single element. Renaming won't actaully disambiguate
       * anything in this case, so skip the work.
       */
      this.renamingIndex.put(prop.getName(), prop.getName());
      return;
    }

    this.renamingIndex.putAll(prop.getName(), clusterNames.values());
    for (Map.Entry usage : prop.getUseSites().entrySet()) {
      Node site = usage.getKey();
      FlatType flatRep = prop.getClusters().find(usage.getValue());
      String newName = clusterNames.get(flatRep);
      if (!Objects.equals(newName, site.getString())) {
        site.setString(newName);
        this.mutationCb.accept(site);
      }
    }
  }

  ImmutableSetMultimap getRenamingIndex() {
    return this.renamingIndex.build();
  }

  /**
   * Creates a unique name for each cluster in {@code prop} and maps it to the cluster
   * representative.
   */
  private static ImmutableMap createAllClusterNames(PropertyClustering prop) {
    return prop.getClusters().allRepresentatives().stream()
        .collect(toImmutableMap(identity(), (r) -> createClusterName(prop, r)));
  }

  private static String createClusterName(PropertyClustering prop, FlatType rep) {
    if (Objects.equals(prop.getExternsClusterRep(), rep)) {
      return prop.getName();
    }

    return "JSC$" + rep.getId() + "_" + prop.getName();
  }

  private static JSError createInvalidationError(CheckLevel level, String name) {
    return JSError.make(
        null, -1, -1, level, PropertyRenamingDiagnostics.INVALIDATION, name, "", "", "");
  }
}