// Copyright 2017 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.annotations.VisibleForTesting;
import com.google.common.base.Functions;
import com.google.common.base.Joiner;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Multimap;
import com.google.common.collect.Sets;
import com.google.devtools.build.lib.analysis.ConfigurationsCollector;
import com.google.devtools.build.lib.analysis.ConfigurationsResult;
import com.google.devtools.build.lib.analysis.Dependency;
import com.google.devtools.build.lib.analysis.DependencyKey;
import com.google.devtools.build.lib.analysis.DependencyKind;
import com.google.devtools.build.lib.analysis.PlatformOptions;
import com.google.devtools.build.lib.analysis.TargetAndConfiguration;
import com.google.devtools.build.lib.analysis.config.transitions.ConfigurationTransition;
import com.google.devtools.build.lib.analysis.config.transitions.NullTransition;
import com.google.devtools.build.lib.analysis.config.transitions.SplitTransition;
import com.google.devtools.build.lib.analysis.config.transitions.TransitionFactory;
import com.google.devtools.build.lib.analysis.config.transitions.TransitionUtil;
import com.google.devtools.build.lib.analysis.skylark.StarlarkTransition;
import com.google.devtools.build.lib.analysis.skylark.StarlarkTransition.TransitionException;
import com.google.devtools.build.lib.cmdline.Label;
import com.google.devtools.build.lib.events.Event;
import com.google.devtools.build.lib.events.ExtendedEventHandler;
import com.google.devtools.build.lib.events.StoredEventHandler;
import com.google.devtools.build.lib.packages.Attribute;
import com.google.devtools.build.lib.packages.AttributeTransitionData;
import com.google.devtools.build.lib.packages.ConfiguredAttributeMapper;
import com.google.devtools.build.lib.packages.Target;
import com.google.devtools.build.lib.packages.TargetUtils;
import com.google.devtools.build.lib.skyframe.BuildConfigurationValue;
import com.google.devtools.build.lib.skyframe.PackageValue;
import com.google.devtools.build.lib.skyframe.PlatformMappingValue;
import com.google.devtools.build.lib.skyframe.TransitiveTargetKey;
import com.google.devtools.build.lib.skyframe.TransitiveTargetValue;
import com.google.devtools.build.lib.util.OrderedSetMultimap;
import com.google.devtools.build.lib.vfs.PathFragment;
import com.google.devtools.build.skyframe.SkyFunction;
import com.google.devtools.build.skyframe.SkyKey;
import com.google.devtools.build.skyframe.ValueOrException;
import com.google.devtools.common.options.OptionsParsingException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedHashMap;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import javax.annotation.Nullable;

/**
 * Turns configuration transition requests into actual configurations.
 *
 * <p>This involves:
 *
 * <ol>
 *   <li>Patching a source configuration's options with the transition
 *   <li>If {@link BuildConfiguration#trimConfigurations} is true, trimming configuration fragments
 *       to only those needed by the destination target and its transitive dependencies
 *   <li>Getting the destination configuration from Skyframe
 * </ol>
 *
 * <p>For the work of determining the transition requests themselves, see {@link
 * TransitionResolver}.
 */
public final class ConfigurationResolver {

  /**
   * Determines the output ordering of each {@code <attribute, depLabel> -> [dep<config1>,
   * dep<config2>, ...]} collection produced by a split transition.
   */
  @VisibleForTesting
  public static final Comparator<Dependency> SPLIT_DEP_ORDERING =
      Comparator.comparing(
              Functions.compose(BuildConfiguration::getMnemonic, Dependency::getConfiguration))
          .thenComparing(
              Functions.compose(BuildConfiguration::checksum, Dependency::getConfiguration));

  // Signals that a Skyframe restart is needed.
  private static class ValueMissingException extends Exception {
    private ValueMissingException() {
      super();
    }
  }

  private final SkyFunction.Environment env;
  private final TargetAndConfiguration ctgValue;
  private final BuildConfiguration hostConfiguration;
  private final BuildOptions defaultBuildOptions;
  private final ImmutableMap<Label, ConfigMatchingProvider> configConditions;

  public ConfigurationResolver(
      SkyFunction.Environment env,
      TargetAndConfiguration ctgValue,
      BuildConfiguration hostConfiguration,
      BuildOptions defaultBuildOptions,
      ImmutableMap<Label, ConfigMatchingProvider> configConditions) {
    this.env = env;
    this.ctgValue = ctgValue;
    this.hostConfiguration = hostConfiguration;
    this.defaultBuildOptions = defaultBuildOptions;
    this.configConditions = configConditions;
  }

  private BuildConfiguration getCurrentConfiguration() {
    return ctgValue.getConfiguration();
  }

  /**
   * Translates a set of {@link DependencyKey} objects with configuration transition requests to the
   * same objects with resolved configurations.
   *
   * <p>This method must preserve the original label ordering of each attribute. For example, if
   * {@code dependencyKeys.get("data")} is {@code [":a", ":b"]}, the resolved variant must also be
   * {@code [":a", ":b"]} in the same order.
   *
   * <p>For split transitions, {@code dependencyKeys.get("data") = [":a", ":b"]} can produce the
   * output {@code [":a"<config1>, ":a"<config2>, ..., ":b"<config1>, ":b"<config2>, ...]}. All
   * instances of ":a" still appear before all instances of ":b". But the {@code [":a"<config1>,
   * ":a"<config2>"]} subset may be in any (deterministic) order. In particular, this may not be the
   * same order as {@link SplitTransition#split}. If needed, this code can be modified to use that
   * order, but that involves more runtime in performance-critical code, so we won't make that
   * change without a clear need.
   *
   * <p>If {@link BuildConfiguration#trimConfigurations()} is true, these configurations only
   * contain the fragments needed by the dep and its transitive closure. Else they unconditionally
   * include all fragments.
   *
   * <p>This method is heavily performance-optimized. Because {@link
   * com.google.devtools.build.lib.skyframe.ConfiguredTargetFunction} calls it over every edge in
   * the configured target graph, small inefficiencies can have observable impact on analysis time.
   * Keep this in mind when making modifications and performance-test any changes you make.
   *
   * @param dependencyKeys the transition requests for each dep and each dependency kind
   * @return a mapping from each dependency kind in the source target to the {@link
   *     BuildConfiguration}s and {@link Label}s for the deps under that dependency kind . Returns
   *     null if not all Skyframe dependencies are available.
   */
  @Nullable
  public OrderedSetMultimap<DependencyKind, Dependency> resolveConfigurations(
      OrderedSetMultimap<DependencyKind, DependencyKey> dependencyKeys)
      throws DependencyEvaluationException, InterruptedException {
    try {
      OrderedSetMultimap<DependencyKind, Dependency> resolvedDeps = OrderedSetMultimap.create();
      for (Map.Entry<DependencyKind, DependencyKey> entry : dependencyKeys.entries()) {
        DependencyKind dependencyKind = entry.getKey();
        DependencyKey dependencyKey = entry.getValue();
        resolvedDeps.putAll(dependencyKind, resolveConfiguration(dependencyKind, dependencyKey));
      }
      return resolvedDeps;
    } catch (ValueMissingException e) {
      return null;
    }
  }

  private ImmutableList<Dependency> resolveConfiguration(
      DependencyKind dependencyKind, DependencyKey dependencyKey)
      throws DependencyEvaluationException, ValueMissingException, InterruptedException {

    Dependency.Builder dependencyBuilder = Dependency.builder().setLabel(dependencyKey.getLabel());

    ConfigurationTransition transition = dependencyKey.getTransition();
    if (transition == NullTransition.INSTANCE) {
      return ImmutableList.of(resolveNullTransition(dependencyBuilder, dependencyKind));
    } else if (transition.isHostTransition()) {
      return ImmutableList.of(resolveHostTransition(dependencyBuilder, dependencyKey));
    }

    // Figure out the required fragments for this dep and its transitive closure.
    Set<Class<? extends Fragment>> depFragments =
        getTransitiveFragments(dependencyKey.getLabel(), getCurrentConfiguration());

    // TODO(gregce): remove the below call once we have confidence trimmed configurations always
    // provide needed fragments. This unnecessarily drags performance on the critical path (up
    // to 0.5% of total analysis time as profiled over a simple cc_binary).
    if (getCurrentConfiguration().trimConfigurations()) {
      checkForMissingFragments(dependencyKind.getAttribute(), dependencyKey, depFragments);
    }

    return resolveGenericTransition(depFragments, dependencyBuilder, dependencyKey);
  }

  private Dependency resolveNullTransition(
      Dependency.Builder dependencyBuilder, DependencyKind dependencyKind)
      throws DependencyEvaluationException, ValueMissingException, InterruptedException {
    // The null configuration can be trivially computed (it's, well, null), so special-case that
    // transition here and skip the rest of the logic. A *lot* of targets have null deps, so
    // this produces real savings. Profiling tests over a simple cc_binary show this saves ~1% of
    // total analysis phase time.
    if (dependencyKind.getAttribute() != null) {
      dependencyBuilder.setTransitionKeys(collectTransitionKeys(dependencyKind.getAttribute()));
    }

    return dependencyBuilder.withNullConfiguration().build();
  }

  private Dependency resolveHostTransition(
      Dependency.Builder dependencyBuilder, DependencyKey dependencyKey)
      throws DependencyEvaluationException {
    // The current rule's host configuration can also be used for the dep. We short-circuit
    // the standard transition logic for host transitions because these transitions are
    // uniquely frequent. It's possible, e.g., for every node in the configured target graph
    // to incur multiple host transitions. So we aggressively optimize to avoid hurting
    // analysis time.
    if (hostConfiguration.trimConfigurationsRetroactively()
        && !dependencyKey.getAspects().isEmpty()) {
      String message =
          ctgValue.getLabel()
              + " has aspects attached, but these are not supported in retroactive"
              + " trimming mode.";
      env.getListener()
          .handle(Event.error(TargetUtils.getLocationMaybe(ctgValue.getTarget()), message));
      throw new DependencyEvaluationException(new InvalidConfigurationException(message));
    }

    return dependencyBuilder
        .setConfiguration(hostConfiguration)
        .setAspects(dependencyKey.getAspects())
        .build();
  }

  private ImmutableList<Dependency> resolveGenericTransition(
      Set<Class<? extends Fragment>> depFragments,
      Dependency.Builder dependencyBuilder,
      DependencyKey dependencyKey)
      throws DependencyEvaluationException, InterruptedException, ValueMissingException {
    Map<String, BuildOptions> toOptions;
    try {
      HashMap<PackageValue.Key, PackageValue> buildSettingPackages =
          StarlarkTransition.getBuildSettingPackages(env, dependencyKey.getTransition());
      if (buildSettingPackages == null) {
        throw new ValueMissingException();
      }
      toOptions =
          applyTransition(
              getCurrentConfiguration().getOptions(),
              dependencyKey.getTransition(),
              buildSettingPackages,
              env.getListener());
    } catch (TransitionException e) {
      throw new DependencyEvaluationException(e);
    }

    if (depFragments.equals(getCurrentConfiguration().fragmentClasses().fragmentClasses())
        && SplitTransition.equals(getCurrentConfiguration().getOptions(), toOptions.values())) {
      // The dep uses the same exact configuration. Let's re-use the current configuration and
      // skip adding a Skyframe dependency edge on it.
      return ImmutableList.of(
          dependencyBuilder
              .setConfiguration(getCurrentConfiguration())
              .setAspects(dependencyKey.getAspects())
              // Explicitly do not set the transition key, since there is only one configuration
              // and it matches the current one. This ignores the transition key set if this
              // was a split transition.
              .build());
    }

    PathFragment platformMappingPath =
        getCurrentConfiguration().getOptions().get(PlatformOptions.class).platformMappings;
    PlatformMappingValue platformMappingValue =
        (PlatformMappingValue) env.getValue(PlatformMappingValue.Key.create(platformMappingPath));
    if (platformMappingValue == null) {
      throw new ValueMissingException();
    }

    Map<String, BuildConfigurationValue.Key> configurationKeys = new HashMap<>();
    try {
      for (Map.Entry<String, BuildOptions> optionsEntry : toOptions.entrySet()) {
        String transitionKey = optionsEntry.getKey();
        BuildConfigurationValue.Key buildConfigurationValueKey =
            BuildConfigurationValue.keyWithPlatformMapping(
                platformMappingValue,
                defaultBuildOptions,
                depFragments,
                BuildOptions.diffForReconstruction(defaultBuildOptions, optionsEntry.getValue()));
        configurationKeys.put(transitionKey, buildConfigurationValueKey);
      }
    } catch (OptionsParsingException e) {
      throw new DependencyEvaluationException(new InvalidConfigurationException(e));
    }

    Map<SkyKey, ValueOrException<InvalidConfigurationException>> depConfigValues =
        env.getValuesOrThrow(configurationKeys.values(), InvalidConfigurationException.class);
    List<Dependency> dependencies = new ArrayList<>();
    try {
      for (Map.Entry<String, BuildConfigurationValue.Key> entry : configurationKeys.entrySet()) {
        String transitionKey = entry.getKey();
        ValueOrException<InvalidConfigurationException> valueOrException =
            depConfigValues.get(entry.getValue());
        if (valueOrException.get() == null) {
          continue;
        }
        BuildConfiguration configuration =
            ((BuildConfigurationValue) valueOrException.get()).getConfiguration();
        if (configuration != null) {
          Dependency resolvedDep =
              dependencyBuilder
                  // Copy the builder so we don't overwrite the other dependencies.
                  .copy()
                  .setConfiguration(configuration)
                  .setAspects(dependencyKey.getAspects())
                  .setTransitionKey(transitionKey)
                  .build();
          dependencies.add(resolvedDep);
        }
      }
      if (env.valuesMissing()) {
        throw new ValueMissingException();
      }
    } catch (InvalidConfigurationException e) {
      throw new DependencyEvaluationException(e);
    }

    Collections.sort(dependencies, SPLIT_DEP_ORDERING);
    return ImmutableList.copyOf(dependencies);
  }

  private ImmutableList<String> collectTransitionKeys(Attribute attribute)
      throws DependencyEvaluationException, ValueMissingException, InterruptedException {
    TransitionFactory<AttributeTransitionData> transitionFactory = attribute.getTransitionFactory();
    if (transitionFactory.isSplit()) {
      AttributeTransitionData transitionData =
          AttributeTransitionData.builder()
              .attributes(
                  ConfiguredAttributeMapper.of(
                      ctgValue.getTarget().getAssociatedRule(), configConditions))
              .build();
      ConfigurationTransition baseTransition = transitionFactory.create(transitionData);
      Map<String, BuildOptions> toOptions;
      try {
        // TODO(jungjw): See if we can dedup getBuildSettingPackages implementations and put
        //  this in applyTransition.
        HashMap<PackageValue.Key, PackageValue> buildSettingPackages =
            StarlarkTransition.getBuildSettingPackages(env, baseTransition);
        if (buildSettingPackages == null) {
          throw new ValueMissingException();
        }
        toOptions =
            applyTransition(
                getCurrentConfiguration().getOptions(),
                baseTransition,
                buildSettingPackages,
                env.getListener());
      } catch (TransitionException e) {
        throw new DependencyEvaluationException(e);
      }
      if (!SplitTransition.equals(getCurrentConfiguration().getOptions(), toOptions.values())) {
        return ImmutableList.copyOf(toOptions.keySet());
      }
    }

    return ImmutableList.of();
  }

  /**
   * Returns the configuration fragments required by a dep and its transitive closure. Returns null
   * if Skyframe dependencies aren't yet available.
   *
   * @param dep label of the dep to check
   * @param parentConfig configuration of the rule depending on the dep
   */
  private ImmutableSet<Class<? extends Fragment>> getTransitiveFragments(
      Label dep, BuildConfiguration parentConfig)
      throws InterruptedException, ValueMissingException {
    if (!parentConfig.trimConfigurations()) {
      return parentConfig.getFragmentsMap().keySet();
    }
    SkyKey fragmentsKey = TransitiveTargetKey.of(dep);
    TransitiveTargetValue transitiveDepInfo = (TransitiveTargetValue) env.getValue(fragmentsKey);
    if (transitiveDepInfo == null) {
      // This should only be possible for tests. In actual runs, this was already called
      // as a routine part of the loading phase.
      // TODO(bazel-team): check this only occurs in a test context.
      throw new ValueMissingException();
    }
    return transitiveDepInfo.getTransitiveConfigFragments().toSet();
  }

  /**
   * Applies a configuration transition over a set of build options.
   *
   * <p>prework - load all default values for read build settings in Starlark transitions (by
   * design, {@link BuildOptions} never holds default values of build settings)
   *
   * <p>postwork - replay events/throw errors from transition implementation function and validate
   * the outputs of the transition
   *
   * @return the build options for the transitioned configuration.
   */
  @VisibleForTesting
  public static Map<String, BuildOptions> applyTransition(
      BuildOptions fromOptions,
      ConfigurationTransition transition,
      Map<PackageValue.Key, PackageValue> buildSettingPackages,
      ExtendedEventHandler eventHandler)
      throws TransitionException {
    boolean doesStarlarkTransition = StarlarkTransition.doesStarlarkTransition(transition);
    if (doesStarlarkTransition) {
      fromOptions =
          addDefaultStarlarkOptions(
              fromOptions,
              StarlarkTransition.getDefaultInputValues(buildSettingPackages, transition));
    }

    // TODO(bazel-team): Add safety-check that this never mutates fromOptions.
    StoredEventHandler handlerWithErrorStatus = new StoredEventHandler();
    Map<String, BuildOptions> result =
        transition.apply(TransitionUtil.restrict(transition, fromOptions), handlerWithErrorStatus);

    if (doesStarlarkTransition) {
      // We use a temporary StoredEventHandler instead of the caller's event handler because
      // StarlarkTransition.validate assumes no errors occurred. We need a StoredEventHandler to be
      // able to check that, and fail out early if there are errors.
      //
      // TODO(bazel-team): harden StarlarkTransition.validate so we can eliminate this step.
      // StarlarkRuleTransitionProviderTest#testAliasedBuildSetting_outputReturnMismatch shows the
      // effect.
      handlerWithErrorStatus.replayOn(eventHandler);
      if (handlerWithErrorStatus.hasErrors()) {
        throw new TransitionException("Errors encountered while applying Starlark transition");
      }
      result = StarlarkTransition.validate(transition, buildSettingPackages, result);
    }
    return result;
  }

  private static BuildOptions addDefaultStarlarkOptions(
      BuildOptions fromOptions, ImmutableMap<Label, Object> buildSettingDefaults) {
    BuildOptions.Builder optionsWithDefaults = null;
    for (Map.Entry<Label, Object> buildSettingDefault : buildSettingDefaults.entrySet()) {
      Label buildSetting = buildSettingDefault.getKey();
      if (!fromOptions.getStarlarkOptions().containsKey(buildSetting)) {
        if (optionsWithDefaults == null) {
          optionsWithDefaults = fromOptions.toBuilder();
        }
        optionsWithDefaults.addStarlarkOption(buildSetting, buildSettingDefault.getValue());
      }
    }
    return optionsWithDefaults == null ? fromOptions : optionsWithDefaults.build();
  }

  /**
   * Checks the config fragments required by a dep against the fragments in its actual
   * configuration. If any are missing, triggers a descriptive "missing fragments" error.
   */
  private void checkForMissingFragments(
      Attribute attribute, DependencyKey dep, Set<Class<? extends Fragment>> expectedDepFragments)
      throws DependencyEvaluationException {
    Set<String> ctgFragmentNames = new HashSet<>();
    for (Fragment fragment : getCurrentConfiguration().getFragmentsMap().values()) {
      ctgFragmentNames.add(fragment.getClass().getSimpleName());
    }
    Set<String> depFragmentNames = new HashSet<>();
    for (Class<? extends Fragment> fragmentClass : expectedDepFragments) {
      depFragmentNames.add(fragmentClass.getSimpleName());
    }
    Set<String> missing = Sets.difference(depFragmentNames, ctgFragmentNames);
    if (!missing.isEmpty()) {
      String msg =
          String.format(
              "%s: dependency %s from attribute \"%s\" is missing required config fragments: %s",
              ctgValue.getLabel(),
              dep.getLabel(),
              attribute == null ? "(null)" : attribute.getName(),
              Joiner.on(", ").join(missing));
      env.getListener().handle(Event.error(msg));
      throw new DependencyEvaluationException(new InvalidConfigurationException(msg));
    }
  }

  /**
   * This method allows resolution of configurations outside of a skyfunction call.
   *
   * <p>Unlike {@link #resolveConfigurations}, this doesn't expect the current context to be
   * evaluating dependencies of a parent target. So this method is also suitable for top-level
   * targets.
   *
   * <p>Resolution consists of two steps:
   *
   * <ol>
   *   <li>Apply the per-target transitions specified in {@code targetsToEvaluate}. This can be
   *       used, e.g., to apply {@link
   *       com.google.devtools.build.lib.analysis.config.transitions.TransitionFactory}s over global
   *       top-level configurations.
   *   <li>(Optionally) trim configurations to only the fragments the targets actually need. This is
   *       triggered by {@link BuildConfiguration#trimConfigurations}.
   * </ol>
   *
   * <p>Preserves the original input order (but merges duplicate nodes that might occur due to
   * top-level configuration transitions) . Uses original (untrimmed, pre-transition) configurations
   * for targets that can't be evaluated (e.g. due to loading phase errors).
   *
   * <p>This is suitable for feeding {@link
   * com.google.devtools.build.lib.skyframe.ConfiguredTargetValue} keys: as general principle {@link
   * com.google.devtools.build.lib.analysis.ConfiguredTarget}s should have exactly as much
   * information in their configurations as they need to evaluate and no more (e.g. there's no need
   * for Android settings in a C++ configured target).
   *
   * @param defaultContext the original targets and starting configurations before applying rule
   *     transitions and trimming. When actual configurations can't be evaluated, these values are
   *     returned as defaults. See TODO below.
   * @param targetsToEvaluate the inputs repackaged as dependencies, including rule-specific
   *     transitions
   * @param eventHandler the error event handler
   * @param configurationsCollector the collector which finds configurations for dependencies
   */
  // TODO(bazel-team): error out early for targets that fail - failed configuration evaluations
  //   should never make it through analysis (and especially not seed ConfiguredTargetValues)
  // TODO(gregce): merge this more with resolveConfigurations? One crucial difference is
  //   resolveConfigurations can null-return on missing deps since it executes inside Skyfunctions.
  // Keep this in sync with {@link PrepareAnalysisPhaseFunction#resolveConfigurations}.
  public static TopLevelTargetsAndConfigsResult getConfigurationsFromExecutor(
      Iterable<TargetAndConfiguration> defaultContext,
      Multimap<BuildConfiguration, DependencyKey> targetsToEvaluate,
      ExtendedEventHandler eventHandler,
      ConfigurationsCollector configurationsCollector)
      throws InvalidConfigurationException {

    Map<Label, Target> labelsToTargets = new HashMap<>();
    for (TargetAndConfiguration targetAndConfig : defaultContext) {
      labelsToTargets.put(targetAndConfig.getLabel(), targetAndConfig.getTarget());
    }

    // Maps <target, originalConfig> pairs to <target, finalConfig> pairs for targets that
    // could be successfully Skyframe-evaluated.
    Map<TargetAndConfiguration, TargetAndConfiguration> successfullyEvaluatedTargets =
        new LinkedHashMap<>();
    boolean hasError = false;
    if (!targetsToEvaluate.isEmpty()) {
      for (BuildConfiguration fromConfig : targetsToEvaluate.keySet()) {
        ConfigurationsResult configurationsResult =
            configurationsCollector.getConfigurations(
                eventHandler, fromConfig.getOptions(), targetsToEvaluate.get(fromConfig));
        hasError |= configurationsResult.hasError();
        for (Map.Entry<DependencyKey, BuildConfiguration> evaluatedTarget :
            configurationsResult.getConfigurationMap().entries()) {
          Target target = labelsToTargets.get(evaluatedTarget.getKey().getLabel());
          successfullyEvaluatedTargets.put(
              new TargetAndConfiguration(target, fromConfig),
              new TargetAndConfiguration(target, evaluatedTarget.getValue()));
        }
      }
    }

    LinkedHashSet<TargetAndConfiguration> result = new LinkedHashSet<>();
    for (TargetAndConfiguration originalInput : defaultContext) {
      if (successfullyEvaluatedTargets.containsKey(originalInput)) {
        // The configuration was successfully evaluated.
        result.add(successfullyEvaluatedTargets.get(originalInput));
      } else {
        // Either the configuration couldn't be determined (e.g. loading phase error) or it's null.
        result.add(originalInput);
      }
    }
    return new TopLevelTargetsAndConfigsResult(result, hasError);
  }

  /**
   * The result of {@link #getConfigurationsFromExecutor} which also registers if an error was
   * recorded.
   */
  public static class TopLevelTargetsAndConfigsResult {
    private final Collection<TargetAndConfiguration> configurations;
    private final boolean hasError;

    public TopLevelTargetsAndConfigsResult(
        Collection<TargetAndConfiguration> configurations, boolean hasError) {
      this.configurations = configurations;
      this.hasError = hasError;
    }

    public boolean hasError() {
      return hasError;
    }

    public Collection<TargetAndConfiguration> getTargetsAndConfigs() {
      return configurations;
    }
  }
}