src/main/java/com/google/devtools/build/lib/analysis/Project.java - bazel - Git at Google

 // Copyright 2024 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;

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

 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Strings;
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.ImmutableMultimap;
 import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.Iterables;
 import com.google.common.collect.Iterators;
 import com.google.common.collect.LinkedListMultimap;
 import com.google.common.collect.ListMultimap;
 import com.google.common.collect.Multimaps;
 import com.google.common.collect.Sets;
 import com.google.devtools.build.lib.analysis.config.BuildOptions;
 import com.google.devtools.build.lib.analysis.config.InvalidConfigurationException;
 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.runtime.ConfigFlagDefinitions;
 import com.google.devtools.build.lib.server.FailureDetails.BuildConfiguration.Code;
 import com.google.devtools.build.lib.skyframe.ProjectFilesLookupValue;
 import com.google.devtools.build.lib.skyframe.ProjectValue;
 import com.google.devtools.build.lib.skyframe.SkyframeExecutor;
 import com.google.devtools.build.lib.skyframe.config.FlagSetValue;
 import com.google.devtools.build.skyframe.EvaluationResult;
 import com.google.devtools.build.skyframe.SkyValue;
 import java.util.Collection;
 import java.util.Iterator;
 import java.util.LinkedHashMap;
 import java.util.Map;
 import java.util.Set;
 import javax.annotation.Nullable;

 /**
  * Container for reading project data.
  *
  * <p>A "project" is a set of related packages that support a common piece of software. For example,
  * "bazel" is a project that includes packages {@code src/main/java/com/google/devtools/build/lib},
  * {@code src/main/java/com/google/devtools/build/lib/analysis}, {@code src/test/cpp}, and more.
  *
  * <p>"Project data" is any useful information that might be associated with a project. Possible
  * consumers include <a
  * href="https://github.com/bazelbuild/bazel/commit/693215317a6732085731809266f63ff0e7fc31a5">
  * Skyfocus</a>> and project-sanctioned build flags (i.e. "these are the correct flags to use with
  * this project").
  *
  * <p>Projects are defined in .scl files that are checked into source control with BUILD files and
  * code. scl stands for "Starlark configuration language". This is a limited subset of Starlark
  * intended to model generic configuration without requiring Bazel to parse it (similar to JSON).
  *
  * <p>This is not the same as {@link com.google.devtools.build.lib.runtime.ProjectFile}. That's an
  * older implementation of the same idea that was built before .scl and .bzl existed. The code here
  * is a rejuvenation of these ideas with more modern APIs.
  */
 // TODO: b/324127050 - Make the co-existence of this and ProjectFile less confusing. ProjectFile is
 //   an outdated API that should be removed.
 public final class Project {
   private Project() {}

   /**
    * The active PROJECT.scls for this build.
    *
    * <p>For example, {@code $ bazel build //foo //bar //baz} could resolve to one, two, or three
    * PROJECT.scls, or a mixed state where only some targets have PROJECT.scls.
    *
    * <p>Consuming code needs to determine if mixed states are valid. People often build multiple
    * projects in a single invocation. We don't want to automatically break those builds if there's
    * still a sound way to build them.
    *
    * @param projectFilesToTargetLabels map of PROJECT.scls to the targets that resolve to them.
    * @param partialProjectBuild true if some of this build's targets have PROJECT.scls and others
    *     don't.
    * @param differentProjectsDetails A descriptive message explaining how different targets resolve
    *     to different PROJECT.scls. Consuming code can use this to provide helpful errors if it
    *     determines the build isn't valid because of this.
    */
   public record ActiveProjects(
       LinkedHashMap<Label, Collection<Label>> projectFilesToTargetLabels,
       boolean partialProjectBuild,
       String differentProjectsDetails) {
     public boolean isEmpty() {
       return projectFilesToTargetLabels.isEmpty();
     }

     /** User-friendly description of this build type, for consumer info/error messaging. */
     public String buildType() {
       if (projectFilesToTargetLabels.size() > 1) {
         return "multi-project build";
       } else if (partialProjectBuild) {
         return "build where only some targets have projects";
       } else if (projectFilesToTargetLabels.size() == 1) {
         return "single-project build";
       } else {
         return "build with no projects";
       }
     }
   }

   /**
    * Returns the canonical project files for a set of targets.
    *
    * <p>If a target matches multiple project files (like {@code a/PROJECT.scl} and {@code
    * a/b/PROJECT.scl}), only the innermost is considered.
    *
    * @param targets targets to resolve project files for
    * @param skyframeExecutor support for SkyFunctions that look up project files
    * @param eventHandler event handler
    * @throws ProjectResolutionException if project resolution fails for any reason
    */
   // TODO: b/324127375 - Support hierarchical project files: [foo/project.scl, foo/bar/project.scl].
   @Nullable
   @VisibleForTesting
   public static ActiveProjects getProjectFiles(
       Collection<Label> targets,
       SkyframeExecutor skyframeExecutor,
       ExtendedEventHandler eventHandler)
       throws ProjectResolutionException {
     // Map targets to their innermost matching project file. Omits targets with no project files.
     ImmutableMap<Label, Label> targetsToProjectFiles =
         // findProjectFiles returns all project files up a target's path (and omits targets with
         // no project files). We just use the first entry, which is the innermost file. For
         // example, given [a/b/PROJECT.scl, a/PROJECT.scl], we just use a/b/PROJECT.scl.
         findProjectFiles(targets, skyframeExecutor, eventHandler).asMap().entrySet().stream()
             .collect(
                 toImmutableMap(Map.Entry::getKey, entry -> entry.getValue().iterator().next()));

     if (targetsToProjectFiles.isEmpty()) {
       // None of the targets have project files.
       return new ActiveProjects(new LinkedHashMap<>(), /* partialProjectBuild= */ false, "");
     }
     Set<Label> targetsWithNoProjectFiles =
         Sets.difference(ImmutableSet.copyOf(targets), targetsToProjectFiles.keySet());

     // Since project files can be aliases to other files, we need to parse them to potentially remap
     // to their references. Also remember the targets that resolved to that project file for clean
     // error reporting.
     LinkedListMultimap<ProjectValue.Key, Label> projectFileKeysToTargets =
         Multimaps.invertFrom(
             Multimaps.forMap(
                 targetsToProjectFiles.entrySet().stream()
                     .collect(
                         toImmutableMap(
                             Map.Entry::getKey, entry -> new ProjectValue.Key(entry.getValue())))),
             LinkedListMultimap.create());

     // Load project file content from Skyframe.
     EvaluationResult<SkyValue> evalResult =
         skyframeExecutor.evaluateSkyKeys(
             eventHandler, projectFileKeysToTargets.keySet(), /* keepGoing= */ false);
     if (evalResult.hasError()) {
       throw new ProjectResolutionException(
           "error loading project files: " + evalResult.getError().getException().getMessage(),
           evalResult.getError().getException());
     }

     // De-duplicate the projectFileKeysToTargets keys by resolving project aliases, and store the
     // resulting canonicalized project-to-targets mapping in canonicalProjectToTargets.
     LinkedHashMap<Label, Collection<Label>> canonicalProjectsToTargets = new LinkedHashMap<>();
     for (var keyToTargets : projectFileKeysToTargets.asMap().entrySet()) {
       canonicalProjectsToTargets.put(
           ((ProjectValue) evalResult.get(keyToTargets.getKey())).getActualProjectFile(),
           keyToTargets.getValue());
     }

     if (canonicalProjectsToTargets.size() != 1) {
       // Targets resolve to different project files.
       return new ActiveProjects(
           canonicalProjectsToTargets,
           !canonicalProjectsToTargets.keySet().isEmpty() && !targetsWithNoProjectFiles.isEmpty(),
           differentProjectFilesError(canonicalProjectsToTargets, targetsWithNoProjectFiles));
     } else {
       Label projectFile = Iterables.getOnlyElement(canonicalProjectsToTargets.keySet());
       eventHandler.handle(
           Event.info(String.format("Reading project settings from %s.", projectFile)));
     }
     if (targetsWithNoProjectFiles.isEmpty()) {
       // All targets resolve to the same canonical project file.
       return new ActiveProjects(canonicalProjectsToTargets, false, "");
     } else {
       // Some targets have project files and some don't.
       return new ActiveProjects(canonicalProjectsToTargets, /* partialProjectBuild= */ true, "");
     }
   }

   /**
    * User-friendly error message for when targets resolve to different project files or only some
    * targets have project files.
    */
   private static String differentProjectFilesError(
       Map<Label, Collection<Label>> canonicalProjectsToTargets,
       Set<Label> targetsWithNoProjectFiles) {
     StringBuilder msgBuilder = new StringBuilder("Targets have different project settings:");
     // Maximum number of "//foo:target -> //foo:PROJECT.scl" entries to show.
     final int maxToShow = 5;

     // Iterate through each project file group (and also the "no project file" group), adding one
     // entry from each group until we reach the max. This samples each group as evenly as possible.
     ListMultimap<Label, Label> groupedResults = LinkedListMultimap.create();
     LinkedHashMap<Label, Iterator<Label>> projectFileToNextTarget = new LinkedHashMap<>();
     for (var entry : canonicalProjectsToTargets.entrySet()) {
       projectFileToNextTarget.put(entry.getKey(), entry.getValue().iterator());
     }
     if (!targetsWithNoProjectFiles.isEmpty()) {
       projectFileToNextTarget.put(null, targetsWithNoProjectFiles.iterator());
     }
     int totalResults = 0;
     LinkedHashMap<Label, Iterator<Label>> nextGroupIteration = projectFileToNextTarget;
     while (totalResults < maxToShow && !nextGroupIteration.isEmpty()) {
       projectFileToNextTarget = nextGroupIteration;
       nextGroupIteration = new LinkedHashMap<>();
       for (var entry : projectFileToNextTarget.entrySet()) {
         Iterator<Label> nextTarget = entry.getValue();
         groupedResults.put(entry.getKey(), nextTarget.next());
         if (nextTarget.hasNext()) {
           nextGroupIteration.put(entry.getKey(), nextTarget);
         }
         totalResults++;
         if (totalResults == maxToShow) {
           break;
         }
       }
     }

     // Report results grouped by PROJECT file.
     for (var group : groupedResults.asMap().entrySet()) {
       String projectFile = group.getKey() == null ? "no project file" : group.getKey().toString();
       for (var target : group.getValue()) {
         msgBuilder.append(String.format("\n  - %s -> %s", target, projectFile));
       }
     }
     int resultsLeft = projectFileToNextTarget.values().stream().mapToInt(Iterators::size).sum();
     if (resultsLeft > 0) {
       msgBuilder.append(String.format("\n  (...and %d more)", resultsLeft));
     }
     return msgBuilder.toString();
   }

   /**
    * Finds and returns the project files for a set of build targets.
    *
    * <p>This walks up each target's package path looking for {@link
    * com.google.devtools.build.lib.skyframe.ProjectFilesLookupFunction#PROJECT_FILE_NAME} files. For
    * example, for {@code //foo/bar/baz:mytarget}, this might look in {@code foo/bar/baz}, {@code
    * foo/bar}, and {@code foo} ("might" because it skips directories that don't have BUILD files -
    * those directories aren't packages).
    *
    * <p>This method doesn't read project file content so it doesn't resolve project file aliases.
    *
    * @return a map from each target to its set of project files, ordered by reverse package depth.
    *     So a project file in {@code foo/bar} appears before a project file in {@code foo}. Targets
    *     with no matching project files aren't in the map.
    */
   // TODO: b/324127050 - Document resolution semantics when this is less experimental.
   @VisibleForTesting
   static ImmutableMultimap<Label, Label> findProjectFiles(
       Collection<Label> targets,
       SkyframeExecutor skyframeExecutor,
       ExtendedEventHandler eventHandler)
       throws ProjectResolutionException {
     // TODO: b/324127050 - Support other repos.
     ImmutableMap<Label, ProjectFilesLookupValue.Key> targetsToSkyKeys =
         targets.stream()
             .collect(
                 toImmutableMap(
                     target -> target,
                     target -> ProjectFilesLookupValue.key(target.getPackageIdentifier())));
     var evalResult =
         skyframeExecutor.evaluateSkyKeys(
             eventHandler, targetsToSkyKeys.values(), /* keepGoing= */ false);
       if (evalResult.hasError()) {
       throw new ProjectResolutionException(
           "Error finding project files", evalResult.getError().getException());
       }

     ImmutableMultimap.Builder<Label, Label> ans = ImmutableMultimap.builder();
     for (var entry : targetsToSkyKeys.entrySet()) {
       ProjectFilesLookupValue containingProjects =
           (ProjectFilesLookupValue) evalResult.get(entry.getValue());
       ans.putAll(entry.getKey(), containingProjects.getProjectFiles());
     }
     return ans.build();
   }

   /**
    * Returns the build options to add to this invocation from its active project files and {@code
    * --scl_config} setting.
    *
    * @param fromOptions input {@link BuildOptions}
    * @param activeProjects the active project files for this build. An empty {@link Optional} means
    *     at least one of this build's targets has no project file. If multiple project files are
    *     active or some targets have project files and others don't, this method checks there's a
    *     sound way to set the desired config and throws an {@link InvalidConfigurationException} if
    *     not.
    * @param sclConfig the {@link CoreOptions.sclConfig} to apply
    * @param allOptionNames the names of every native option the parser recognizes, in {@code "name"}
    *     form. Not all entries are {@link BuildOptions}.
    * @param userOptions options that were set by users (vs. global bazelrcs), in name=value form
    * @param configFlagDefinitions definitions of {@code --config=foo} for this build. Null or an
    *     empty string means use the project-default config if set, otherwise no-op.
    * @param enforceCanonicalConfigs if false, project-based flag resolution is disabled
    * @param eventHandler handler for non-fatal project-parsing messaging
    * @param skyframeExecutor executor for Skyframe evaluation
    * @return the options to add to. Caller is responsible for modifying the original build options
    *     with these additions.
    * @throws InvalidConfigurationException if the desired {@code --scl_config} can't be applied in a
    *     supported way
    */
   public static ImmutableSet<String> applySclConfig(
       BuildOptions fromOptions,
       Project.ActiveProjects activeProjects,
       String sclConfig,
       ImmutableSet<String> allOptionNames,
       ImmutableMap<String, String> userOptions,
       ConfigFlagDefinitions configFlagDefinitions,
       boolean enforceCanonicalConfigs,
       ExtendedEventHandler eventHandler,
       SkyframeExecutor skyframeExecutor)
       throws InvalidConfigurationException {
     var flagSetKeys =
         activeProjects.projectFilesToTargetLabels.keySet().stream()
             .map(
                 p ->
                     FlagSetValue.Key.create(
                         ImmutableSet.copyOf(activeProjects.projectFilesToTargetLabels.get(p)),
                         p,
                         sclConfig,
                         fromOptions,
                         allOptionNames,
                         userOptions,
                         configFlagDefinitions,
                         enforceCanonicalConfigs))
             .collect(toImmutableSet());
     EvaluationResult<SkyValue> result =
         skyframeExecutor.evaluateSkyKeys(eventHandler, flagSetKeys, /* keepGoing= */ false);
     if (result.hasError()) {
       throw new InvalidConfigurationException(
           "Cannot parse options: " + result.getError().getException().getMessage(),
           Code.INVALID_BUILD_OPTIONS);
     }

     // Permit multiple configs as long as they all produce the same value, ignoring projects with
     // no project files.
     ImmutableSet<ImmutableSet<String>> uniqueConfigs =
         result.values().stream()
             .map(v -> ((FlagSetValue) v).getOptionsFromFlagset())
             .collect(toImmutableSet());
     if (uniqueConfigs.size() > 1) {
       if (!Strings.isNullOrEmpty(sclConfig)) {
         throw new InvalidConfigurationException(
             "--scl_config=%s resolves to conflicting flagsets: %s"
                 .formatted(sclConfig, activeProjects.differentProjectsDetails),
             Code.INVALID_BUILD_OPTIONS);
       }
       throw new InvalidConfigurationException(
           "Mismatching default configs for a %s. %s"
               .formatted(activeProjects.buildType(), activeProjects.differentProjectsDetails),
           Code.INVALID_BUILD_OPTIONS);
     }

     FlagSetValue value = (FlagSetValue) result.values().iterator().next();
     value.getPersistentMessages().forEach(eventHandler::handle);
     // Options from the selected project config.
     return value.getOptionsFromFlagset();
   }
 }
	// Copyright 2024 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;

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

	import com.google.common.annotations.VisibleForTesting;
	import com.google.common.base.Strings;
	import com.google.common.collect.ImmutableMap;
	import com.google.common.collect.ImmutableMultimap;
	import com.google.common.collect.ImmutableSet;
	import com.google.common.collect.Iterables;
	import com.google.common.collect.Iterators;
	import com.google.common.collect.LinkedListMultimap;
	import com.google.common.collect.ListMultimap;
	import com.google.common.collect.Multimaps;
	import com.google.common.collect.Sets;
	import com.google.devtools.build.lib.analysis.config.BuildOptions;
	import com.google.devtools.build.lib.analysis.config.InvalidConfigurationException;
	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.runtime.ConfigFlagDefinitions;
	import com.google.devtools.build.lib.server.FailureDetails.BuildConfiguration.Code;
	import com.google.devtools.build.lib.skyframe.ProjectFilesLookupValue;
	import com.google.devtools.build.lib.skyframe.ProjectValue;
	import com.google.devtools.build.lib.skyframe.SkyframeExecutor;
	import com.google.devtools.build.lib.skyframe.config.FlagSetValue;
	import com.google.devtools.build.skyframe.EvaluationResult;
	import com.google.devtools.build.skyframe.SkyValue;
	import java.util.Collection;
	import java.util.Iterator;
	import java.util.LinkedHashMap;
	import java.util.Map;
	import java.util.Set;
	import javax.annotation.Nullable;

	/**
	* Container for reading project data.
	*
	* <p>A "project" is a set of related packages that support a common piece of software. For example,
	* "bazel" is a project that includes packages {@code src/main/java/com/google/devtools/build/lib},
	* {@code src/main/java/com/google/devtools/build/lib/analysis}, {@code src/test/cpp}, and more.
	*
	* <p>"Project data" is any useful information that might be associated with a project. Possible
	* consumers include <a
	* href="https://github.com/bazelbuild/bazel/commit/693215317a6732085731809266f63ff0e7fc31a5">
	* Skyfocus</a>> and project-sanctioned build flags (i.e. "these are the correct flags to use with
	* this project").
	*
	* <p>Projects are defined in .scl files that are checked into source control with BUILD files and
	* code. scl stands for "Starlark configuration language". This is a limited subset of Starlark
	* intended to model generic configuration without requiring Bazel to parse it (similar to JSON).
	*
	* <p>This is not the same as {@link com.google.devtools.build.lib.runtime.ProjectFile}. That's an
	* older implementation of the same idea that was built before .scl and .bzl existed. The code here
	* is a rejuvenation of these ideas with more modern APIs.
	*/
	// TODO: b/324127050 - Make the co-existence of this and ProjectFile less confusing. ProjectFile is
	// an outdated API that should be removed.
	public final class Project {
	private Project() {}

	/**
	* The active PROJECT.scls for this build.
	*
	* <p>For example, {@code $ bazel build //foo //bar //baz} could resolve to one, two, or three
	* PROJECT.scls, or a mixed state where only some targets have PROJECT.scls.
	*
	* <p>Consuming code needs to determine if mixed states are valid. People often build multiple
	* projects in a single invocation. We don't want to automatically break those builds if there's
	* still a sound way to build them.
	*
	* @param projectFilesToTargetLabels map of PROJECT.scls to the targets that resolve to them.
	* @param partialProjectBuild true if some of this build's targets have PROJECT.scls and others
	* don't.
	* @param differentProjectsDetails A descriptive message explaining how different targets resolve
	* to different PROJECT.scls. Consuming code can use this to provide helpful errors if it
	* determines the build isn't valid because of this.
	*/
	public record ActiveProjects(
	LinkedHashMap<Label, Collection<Label>> projectFilesToTargetLabels,
	boolean partialProjectBuild,
	String differentProjectsDetails) {
	public boolean isEmpty() {
	return projectFilesToTargetLabels.isEmpty();
	}

	/** User-friendly description of this build type, for consumer info/error messaging. */
	public String buildType() {
	if (projectFilesToTargetLabels.size() > 1) {
	return "multi-project build";
	} else if (partialProjectBuild) {
	return "build where only some targets have projects";
	} else if (projectFilesToTargetLabels.size() == 1) {
	return "single-project build";
	} else {
	return "build with no projects";
	}
	}
	}

	/**
	* Returns the canonical project files for a set of targets.
	*
	* <p>If a target matches multiple project files (like {@code a/PROJECT.scl} and {@code
	* a/b/PROJECT.scl}), only the innermost is considered.
	*
	* @param targets targets to resolve project files for
	* @param skyframeExecutor support for SkyFunctions that look up project files
	* @param eventHandler event handler
	* @throws ProjectResolutionException if project resolution fails for any reason
	*/
	// TODO: b/324127375 - Support hierarchical project files: [foo/project.scl, foo/bar/project.scl].
	@Nullable
	@VisibleForTesting
	public static ActiveProjects getProjectFiles(
	Collection<Label> targets,
	SkyframeExecutor skyframeExecutor,
	ExtendedEventHandler eventHandler)
	throws ProjectResolutionException {
	// Map targets to their innermost matching project file. Omits targets with no project files.
	ImmutableMap<Label, Label> targetsToProjectFiles =
	// findProjectFiles returns all project files up a target's path (and omits targets with
	// no project files). We just use the first entry, which is the innermost file. For
	// example, given [a/b/PROJECT.scl, a/PROJECT.scl], we just use a/b/PROJECT.scl.
	findProjectFiles(targets, skyframeExecutor, eventHandler).asMap().entrySet().stream()
	.collect(
	toImmutableMap(Map.Entry::getKey, entry -> entry.getValue().iterator().next()));

	if (targetsToProjectFiles.isEmpty()) {
	// None of the targets have project files.
	return new ActiveProjects(new LinkedHashMap<>(), /* partialProjectBuild= */ false, "");
	}
	Set<Label> targetsWithNoProjectFiles =
	Sets.difference(ImmutableSet.copyOf(targets), targetsToProjectFiles.keySet());

	// Since project files can be aliases to other files, we need to parse them to potentially remap
	// to their references. Also remember the targets that resolved to that project file for clean
	// error reporting.
	LinkedListMultimap<ProjectValue.Key, Label> projectFileKeysToTargets =
	Multimaps.invertFrom(
	Multimaps.forMap(
	targetsToProjectFiles.entrySet().stream()
	.collect(
	toImmutableMap(
	Map.Entry::getKey, entry -> new ProjectValue.Key(entry.getValue())))),
	LinkedListMultimap.create());

	// Load project file content from Skyframe.
	EvaluationResult<SkyValue> evalResult =
	skyframeExecutor.evaluateSkyKeys(
	eventHandler, projectFileKeysToTargets.keySet(), /* keepGoing= */ false);
	if (evalResult.hasError()) {
	throw new ProjectResolutionException(
	"error loading project files: " + evalResult.getError().getException().getMessage(),
	evalResult.getError().getException());
	}

	// De-duplicate the projectFileKeysToTargets keys by resolving project aliases, and store the
	// resulting canonicalized project-to-targets mapping in canonicalProjectToTargets.
	LinkedHashMap<Label, Collection<Label>> canonicalProjectsToTargets = new LinkedHashMap<>();
	for (var keyToTargets : projectFileKeysToTargets.asMap().entrySet()) {
	canonicalProjectsToTargets.put(
	((ProjectValue) evalResult.get(keyToTargets.getKey())).getActualProjectFile(),
	keyToTargets.getValue());
	}

	if (canonicalProjectsToTargets.size() != 1) {
	// Targets resolve to different project files.
	return new ActiveProjects(
	canonicalProjectsToTargets,
	!canonicalProjectsToTargets.keySet().isEmpty() && !targetsWithNoProjectFiles.isEmpty(),
	differentProjectFilesError(canonicalProjectsToTargets, targetsWithNoProjectFiles));
	} else {
	Label projectFile = Iterables.getOnlyElement(canonicalProjectsToTargets.keySet());
	eventHandler.handle(
	Event.info(String.format("Reading project settings from %s.", projectFile)));
	}
	if (targetsWithNoProjectFiles.isEmpty()) {
	// All targets resolve to the same canonical project file.
	return new ActiveProjects(canonicalProjectsToTargets, false, "");
	} else {
	// Some targets have project files and some don't.
	return new ActiveProjects(canonicalProjectsToTargets, /* partialProjectBuild= */ true, "");
	}
	}

	/**
	* User-friendly error message for when targets resolve to different project files or only some
	* targets have project files.
	*/
	private static String differentProjectFilesError(
	Map<Label, Collection<Label>> canonicalProjectsToTargets,
	Set<Label> targetsWithNoProjectFiles) {
	StringBuilder msgBuilder = new StringBuilder("Targets have different project settings:");
	// Maximum number of "//foo:target -> //foo:PROJECT.scl" entries to show.
	final int maxToShow = 5;

	// Iterate through each project file group (and also the "no project file" group), adding one
	// entry from each group until we reach the max. This samples each group as evenly as possible.
	ListMultimap<Label, Label> groupedResults = LinkedListMultimap.create();
	LinkedHashMap<Label, Iterator<Label>> projectFileToNextTarget = new LinkedHashMap<>();
	for (var entry : canonicalProjectsToTargets.entrySet()) {
	projectFileToNextTarget.put(entry.getKey(), entry.getValue().iterator());
	}
	if (!targetsWithNoProjectFiles.isEmpty()) {
	projectFileToNextTarget.put(null, targetsWithNoProjectFiles.iterator());
	}
	int totalResults = 0;
	LinkedHashMap<Label, Iterator<Label>> nextGroupIteration = projectFileToNextTarget;
	while (totalResults < maxToShow && !nextGroupIteration.isEmpty()) {
	projectFileToNextTarget = nextGroupIteration;
	nextGroupIteration = new LinkedHashMap<>();
	for (var entry : projectFileToNextTarget.entrySet()) {
	Iterator<Label> nextTarget = entry.getValue();
	groupedResults.put(entry.getKey(), nextTarget.next());
	if (nextTarget.hasNext()) {
	nextGroupIteration.put(entry.getKey(), nextTarget);
	}
	totalResults++;
	if (totalResults == maxToShow) {
	break;
	}
	}
	}

	// Report results grouped by PROJECT file.
	for (var group : groupedResults.asMap().entrySet()) {
	String projectFile = group.getKey() == null ? "no project file" : group.getKey().toString();
	for (var target : group.getValue()) {
	msgBuilder.append(String.format("\n - %s -> %s", target, projectFile));
	}
	}
	int resultsLeft = projectFileToNextTarget.values().stream().mapToInt(Iterators::size).sum();
	if (resultsLeft > 0) {
	msgBuilder.append(String.format("\n (...and %d more)", resultsLeft));
	}
	return msgBuilder.toString();
	}

	/**
	* Finds and returns the project files for a set of build targets.
	*
	* <p>This walks up each target's package path looking for {@link
	* com.google.devtools.build.lib.skyframe.ProjectFilesLookupFunction#PROJECT_FILE_NAME} files. For
	* example, for {@code //foo/bar/baz:mytarget}, this might look in {@code foo/bar/baz}, {@code
	* foo/bar}, and {@code foo} ("might" because it skips directories that don't have BUILD files -
	* those directories aren't packages).
	*
	* <p>This method doesn't read project file content so it doesn't resolve project file aliases.
	*
	* @return a map from each target to its set of project files, ordered by reverse package depth.
	* So a project file in {@code foo/bar} appears before a project file in {@code foo}. Targets
	* with no matching project files aren't in the map.
	*/
	// TODO: b/324127050 - Document resolution semantics when this is less experimental.
	@VisibleForTesting
	static ImmutableMultimap<Label, Label> findProjectFiles(
	Collection<Label> targets,
	SkyframeExecutor skyframeExecutor,
	ExtendedEventHandler eventHandler)
	throws ProjectResolutionException {
	// TODO: b/324127050 - Support other repos.
	ImmutableMap<Label, ProjectFilesLookupValue.Key> targetsToSkyKeys =
	targets.stream()
	.collect(
	toImmutableMap(
	target -> target,
	target -> ProjectFilesLookupValue.key(target.getPackageIdentifier())));
	var evalResult =
	skyframeExecutor.evaluateSkyKeys(
	eventHandler, targetsToSkyKeys.values(), /* keepGoing= */ false);
	if (evalResult.hasError()) {
	throw new ProjectResolutionException(
	"Error finding project files", evalResult.getError().getException());
	}

	ImmutableMultimap.Builder<Label, Label> ans = ImmutableMultimap.builder();
	for (var entry : targetsToSkyKeys.entrySet()) {
	ProjectFilesLookupValue containingProjects =
	(ProjectFilesLookupValue) evalResult.get(entry.getValue());
	ans.putAll(entry.getKey(), containingProjects.getProjectFiles());
	}
	return ans.build();
	}

	/**
	* Returns the build options to add to this invocation from its active project files and {@code
	* --scl_config} setting.
	*
	* @param fromOptions input {@link BuildOptions}
	* @param activeProjects the active project files for this build. An empty {@link Optional} means
	* at least one of this build's targets has no project file. If multiple project files are
	* active or some targets have project files and others don't, this method checks there's a
	* sound way to set the desired config and throws an {@link InvalidConfigurationException} if
	* not.
	* @param sclConfig the {@link CoreOptions.sclConfig} to apply
	* @param allOptionNames the names of every native option the parser recognizes, in {@code "name"}
	* form. Not all entries are {@link BuildOptions}.
	* @param userOptions options that were set by users (vs. global bazelrcs), in name=value form
	* @param configFlagDefinitions definitions of {@code --config=foo} for this build. Null or an
	* empty string means use the project-default config if set, otherwise no-op.
	* @param enforceCanonicalConfigs if false, project-based flag resolution is disabled
	* @param eventHandler handler for non-fatal project-parsing messaging
	* @param skyframeExecutor executor for Skyframe evaluation
	* @return the options to add to. Caller is responsible for modifying the original build options
	* with these additions.
	* @throws InvalidConfigurationException if the desired {@code --scl_config} can't be applied in a
	* supported way
	*/
	public static ImmutableSet<String> applySclConfig(
	BuildOptions fromOptions,
	Project.ActiveProjects activeProjects,
	String sclConfig,
	ImmutableSet<String> allOptionNames,
	ImmutableMap<String, String> userOptions,
	ConfigFlagDefinitions configFlagDefinitions,
	boolean enforceCanonicalConfigs,
	ExtendedEventHandler eventHandler,
	SkyframeExecutor skyframeExecutor)
	throws InvalidConfigurationException {
	var flagSetKeys =
	activeProjects.projectFilesToTargetLabels.keySet().stream()
	.map(
	p ->
	FlagSetValue.Key.create(
	ImmutableSet.copyOf(activeProjects.projectFilesToTargetLabels.get(p)),
	p,
	sclConfig,
	fromOptions,
	allOptionNames,
	userOptions,
	configFlagDefinitions,
	enforceCanonicalConfigs))
	.collect(toImmutableSet());
	EvaluationResult<SkyValue> result =
	skyframeExecutor.evaluateSkyKeys(eventHandler, flagSetKeys, /* keepGoing= */ false);
	if (result.hasError()) {
	throw new InvalidConfigurationException(
	"Cannot parse options: " + result.getError().getException().getMessage(),
	Code.INVALID_BUILD_OPTIONS);
	}

	// Permit multiple configs as long as they all produce the same value, ignoring projects with
	// no project files.
	ImmutableSet<ImmutableSet<String>> uniqueConfigs =
	result.values().stream()
	.map(v -> ((FlagSetValue) v).getOptionsFromFlagset())
	.collect(toImmutableSet());
	if (uniqueConfigs.size() > 1) {
	if (!Strings.isNullOrEmpty(sclConfig)) {
	throw new InvalidConfigurationException(
	"--scl_config=%s resolves to conflicting flagsets: %s"
	.formatted(sclConfig, activeProjects.differentProjectsDetails),
	Code.INVALID_BUILD_OPTIONS);
	}
	throw new InvalidConfigurationException(
	"Mismatching default configs for a %s. %s"
	.formatted(activeProjects.buildType(), activeProjects.differentProjectsDetails),
	Code.INVALID_BUILD_OPTIONS);
	}

	FlagSetValue value = (FlagSetValue) result.values().iterator().next();
	value.getPersistentMessages().forEach(eventHandler::handle);
	// Options from the selected project config.
	return value.getOptionsFromFlagset();
	}
	}