src/main/java/com/google/devtools/build/lib/analysis/config/ConfigMatchingProvider.java

// Copyright 2014 The Bazel Authors. All rights reserved.
//
// 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.devtools.build.lib.analysis.config;

import com.google.common.collect.ImmutableMultimap;
import com.google.common.collect.ImmutableSet;
import com.google.devtools.build.lib.analysis.TransitiveInfoProvider;
import com.google.devtools.build.lib.cmdline.Label;
import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
import com.google.devtools.build.lib.skyframe.serialization.autocodec.AutoCodec;
import java.util.Map;
import java.util.Set;

/**
 * A "configuration target" that asserts whether or not it matches the configuration it's bound to.
 *
 * <p>This can be used, e.g., to declare a BUILD target that defines the conditions which trigger a
 * configurable attribute branch. In general, this can be used to trigger for any user-configurable
 * build behavior.
 */
@Immutable
@AutoCodec
public final class ConfigMatchingProvider implements TransitiveInfoProvider {
  private final Label label;
  private final ImmutableMultimap<String, String> settingsMap;
  private final Map<Label, String> flagSettingsMap;
  private final boolean matches;

  /**
   * @param label the build label corresponding to this matcher
   * @param settingsMap the condition settings that trigger this matcher
   * @param flagSettingsMap the label-keyed settings that trigger this matcher
   * @param matches whether or not this matcher matches the configuration associated with its
   *     configured target
   */
  @AutoCodec.Instantiator
  public ConfigMatchingProvider(
      Label label,
      ImmutableMultimap<String, String> settingsMap,
      Map<Label, String> flagSettingsMap,
      boolean matches) {
    this.label = label;
    this.settingsMap = settingsMap;
    this.flagSettingsMap = flagSettingsMap;
    this.matches = matches;
  }

  /**
   * The target's label.
   */
  public Label label() {
    return label;
  }

  /**
   * Whether or not the configuration criteria defined by this target match
   * its actual configuration.
   */
  public boolean matches() {
    return matches;
  }

  /**
   * Returns true if this matcher's conditions are a proper superset of another matcher's
   * conditions, i.e. if this matcher is a specialization of the other one.
   */
  public boolean refines(ConfigMatchingProvider other) {
    Set<Map.Entry<String, String>> settings = ImmutableSet.copyOf(settingsMap.entries());
    Set<Map.Entry<String, String>> otherSettings = ImmutableSet.copyOf(other.settingsMap.entries());
    Set<Map.Entry<Label, String>> flagSettings = flagSettingsMap.entrySet();
    Set<Map.Entry<Label, String>> otherFlagSettings = other.flagSettingsMap.entrySet();

    if (!settings.containsAll(otherSettings)) {
      // not a superset
      return false;
    }

    if (!flagSettings.containsAll(otherFlagSettings)) {
      // not a superset
      return false;
    }

    if (!(settings.size() > otherSettings.size()
        || flagSettings.size() > otherFlagSettings.size())) {
      // not a proper superset
      return false;
    }

    return true;
  }

  /** Format this provider as its label. */
  public String toString() {
    return label.toString();
  }
}