Add basic incompatible target skipping

This patch aims to implement a basic version of incompatible target
skipping outlined here:
https://docs.google.com/document/d/12n5QNHmFSkuh5yAbdEex64ot4hRgR-moL1zRimU7wHQ/edit?usp=sharing

The implementation in this patch supports only "top level" target
skipping. In other words we only filter out targets if they are
globbed as part of an invocation like "bazel build //...".

The following features are not yet implemented:
- Filtering targets based on transitive dependencies. For example, if
  //a:b depends on //c:d an invocation of "bazel build //a/..." will
  still build //c:d even if it is incompatible with the current
  platform.
- Being able to select() on constraint values. For example, it's not
  possible to select() based on whether or not GCC is being used.
  Discussion of this aspect of the proposal is ongoing:
  https://groups.google.com/d/msg/bazel-dev/xK7diubpljQ/s3KSRwTWAQAJ

The goal is to implement the missing features in follow-up patches.

src/main/java/com/google/devtools/build/lib/analysis/BUILD

@@ -328,6 +328,7 @@ java_library(
         ":extra/extra_action_info_file_write_action",
         ":extra_action_artifacts_provider",
         ":file_provider",
+        ":incompatible_platform_provider",
         ":inconsistent_aspect_order_exception",
         ":label_and_location",
         ":label_expander",
@@ -378,6 +379,7 @@ java_library(
         "//src/main/java/com/google/devtools/build/lib/actions:fileset_output_symlink",
         "//src/main/java/com/google/devtools/build/lib/actions:localhost_capacity",
         "//src/main/java/com/google/devtools/build/lib/analysis/platform",
+        "//src/main/java/com/google/devtools/build/lib/analysis/platform:utils",
         "//src/main/java/com/google/devtools/build/lib/analysis/stringtemplate",
         "//src/main/java/com/google/devtools/build/lib/bugreport",
         "//src/main/java/com/google/devtools/build/lib/buildeventstream",
@@ -778,6 +780,15 @@ java_library(
     ],
 )
 
+java_library(
+    name = "incompatible_platform_provider",
+    srcs = ["IncompatiblePlatformProvider.java"],
+    deps = [
+        ":transitive_info_provider",
+        "//src/main/java/com/google/devtools/build/lib/concurrent",
+    ],
+)
+
 java_library(
     name = "inconsistent_aspect_order_exception",
     srcs = ["InconsistentAspectOrderException.java"],
@@ -1982,6 +1993,7 @@ java_library(
     srcs = ["constraints/TopLevelConstraintSemantics.java"],
     deps = [
         ":analysis_cluster",
+        ":incompatible_platform_provider",
         ":config/build_configuration",
         ":configured_target",
         ":constraints/constraint_semantics",

src/main/java/com/google/devtools/build/lib/analysis/BaseRuleClasses.java

@@ -34,6 +34,7 @@
 import com.google.devtools.build.lib.analysis.config.HostTransition;
 import com.google.devtools.build.lib.analysis.config.RunUnder;
 import com.google.devtools.build.lib.analysis.constraints.ConstraintConstants;
+import com.google.devtools.build.lib.analysis.platform.ConstraintValueInfo;
 import com.google.devtools.build.lib.analysis.test.TestConfiguration;
 import com.google.devtools.build.lib.cmdline.Label;
 import com.google.devtools.build.lib.packages.Attribute;
@@ -327,6 +328,14 @@ public static RuleClass.Builder commonCoreAndStarlarkAttributes(RuleClass.Builde
                 .dontCheckConstraints()
                 .nonconfigurable(
                     "special logic for constraints and select: see ConstraintSemantics"))
+        /* <!-- #BLAZE_RULE(toolchain).ATTRIBUTE(target_compatible_with) -->
+        A list of <code>constraint_value</code>s that must be satisfied by the target platform in
+        order for this toolchain to be selected for a target building for that platform.
+        <!-- #END_BLAZE_RULE.ATTRIBUTE --> */
+        .add(
+            attr("target_compatible_with", LABEL_LIST)
+                .mandatoryProviders(ConstraintValueInfo.PROVIDER.id())
+                .allowedFileTypes(FileTypeSet.NO_FILE))
         .add(
             attr(RuleClass.CONFIG_SETTING_DEPS_ATTRIBUTE, LABEL_LIST)
                 .nonconfigurable("stores configurability keys"))

src/main/java/com/google/devtools/build/lib/analysis/BuildView.java

@@ -212,6 +212,7 @@ public AnalysisResult update(
       TargetPatternPhaseValue loadingResult,
       BuildOptions targetOptions,
       Set<String> multiCpu,
+      List<String> requestedTargetPatterns,
       List<String> aspects,
       AnalysisOptions viewOptions,
       boolean keepGoing,
@@ -420,6 +421,22 @@ public AnalysisResult update(
       skyframeBuildView.clearInvalidatedConfiguredTargets();
     }
 
+    TopLevelConstraintSemantics topLevelConstraintSemantics =
+        new TopLevelConstraintSemantics(
+            skyframeExecutor.getPackageManager(),
+            input -> skyframeExecutor.getConfiguration(eventHandler, input),
+            eventHandler);
+
+    TopLevelConstraintSemantics.PlatformRestrictionsResult platformRestrictions =
+        topLevelConstraintSemantics.checkPlatformRestrictions(
+            skyframeAnalysisResult.getConfiguredTargets(), requestedTargetPatterns, keepGoing);
+
+    if (platformRestrictions.targetsWithErrors.size() > 0) {
+      skyframeAnalysisResult =
+          skyframeAnalysisResult.withAdditionalErroredTargets(
+              ImmutableSet.copyOf(platformRestrictions.targetsWithErrors));
+    }
+
     int numTargetsToAnalyze = topLevelTargetsWithConfigs.size();
     int numSuccessful = skyframeAnalysisResult.getConfiguredTargets().size();
     if (0 < numSuccessful && numSuccessful < numTargetsToAnalyze) {
@@ -430,11 +447,11 @@ public AnalysisResult update(
     }
 
     Set<ConfiguredTarget> targetsToSkip =
-        new TopLevelConstraintSemantics(
-                skyframeExecutor.getPackageManager(),
-                input -> skyframeExecutor.getConfiguration(eventHandler, input),
-                eventHandler)
-            .checkTargetEnvironmentRestrictions(skyframeAnalysisResult.getConfiguredTargets());
+        ImmutableSet.copyOf(
+            Sets.union(
+                topLevelConstraintSemantics.checkTargetEnvironmentRestrictions(
+                    skyframeAnalysisResult.getConfiguredTargets()),
+                platformRestrictions.targetsToSkip));
 
     AnalysisResult result =
         createResult(

src/main/java/com/google/devtools/build/lib/analysis/ConfiguredTargetFactory.java

@@ -35,6 +35,8 @@
 import com.google.devtools.build.lib.analysis.configuredtargets.OutputFileConfiguredTarget;
 import com.google.devtools.build.lib.analysis.configuredtargets.PackageGroupConfiguredTarget;
 import com.google.devtools.build.lib.analysis.configuredtargets.RuleConfiguredTarget;
+import com.google.devtools.build.lib.analysis.platform.ConstraintValueInfo;
+import com.google.devtools.build.lib.analysis.platform.PlatformProviderUtils;
 import com.google.devtools.build.lib.analysis.starlark.StarlarkRuleConfiguredTargetUtil;
 import com.google.devtools.build.lib.analysis.test.AnalysisFailure;
 import com.google.devtools.build.lib.analysis.test.AnalysisFailureInfo;
@@ -318,6 +320,12 @@ private ConfiguredTarget createRule(
                     prerequisiteMap.values()))
             .build();
 
+    ConfiguredTarget incompatibleTarget =
+        incompatibleConfiguredTarget(ruleContext, prerequisiteMap);
+    if (incompatibleTarget != null) {
+      return incompatibleTarget;
+    }
+
     List<NestedSet<AnalysisFailure>> analysisFailures = depAnalysisFailures(ruleContext);
     if (!analysisFailures.isEmpty()) {
       return erroredConfiguredTargetWithFailures(ruleContext, analysisFailures);
@@ -372,6 +380,89 @@ private ConfiguredTarget createRule(
     }
   }
 
+  // TODO(phil): Document this.
+  // TODO(phil): Move this into ConstraintSemantics somehow.
+  @Nullable
+  private ConfiguredTarget incompatibleConfiguredTarget(
+      RuleContext ruleContext,
+      OrderedSetMultimap<DependencyKind, ConfiguredTargetAndData> prerequisiteMap)
+      throws ActionConflictException {
+    if (!"toolchain".equals(ruleContext.getRule().getRuleClass())) {
+      boolean isIncompatible = false;
+
+      // This is incompatible if one of the dependencies is as well.
+      for (ConfiguredTargetAndData infoCollection : prerequisiteMap.values()) {
+        ConfiguredTarget dependency = infoCollection.getConfiguredTarget();
+        if (dependency instanceof OutputFileConfiguredTarget) {
+          // For generated files, we want to query the generating rule for providers. genrule() for
+          // example doesn't attach providers like IncompatiblePlatformProvider to its outputs.
+          dependency = ((OutputFileConfiguredTarget)dependency).getGeneratingRule();
+        }
+        if (dependency.getProvider(IncompatiblePlatformProvider.class) != null) {
+          isIncompatible = true;
+        }
+      }
+
+      // This is incompatible if explicitly specified to be.
+      if (!isIncompatible && ruleContext.attributes().has("target_compatible_with")) {
+        Iterable<ConstraintValueInfo> constraintValues =
+            PlatformProviderUtils.constraintValues(
+                ruleContext.getPrerequisites("target_compatible_with", TransitionMode.DONT_CHECK));
+        for (ConstraintValueInfo constraintValue : constraintValues) {
+          if (!ruleContext.targetPlatformHasConstraint(constraintValue)) {
+            isIncompatible = true;
+          }
+        }
+      }
+
+      if (isIncompatible) {
+        // Create a dummy ConfiguredTarget that has the IncompatiblePlatformProvider set.
+        ImmutableList<Artifact> outputArtifacts = ruleContext.getOutputArtifacts();
+
+        if (ruleContext.isTestTarget() && outputArtifacts.size() == 0) {
+          // TODO(philsc): Figure out how to avoid this. Right now some test targets require the
+          // RunfilesSupport to be added to the RuleConfiguredTargetBuilder. E.g. sh_test requires
+          // this while cc_test does not.
+          outputArtifacts = ImmutableList.of(ruleContext.createOutputArtifact());
+        }
+
+        NestedSet<Artifact> filesToBuild =
+            NestedSetBuilder.<Artifact>stableOrder().addAll(outputArtifacts).build();
+
+        Runfiles.Builder runfilesBuilder =
+            new Runfiles.Builder(
+                ruleContext.getWorkspaceName(),
+                ruleContext.getConfiguration().legacyExternalRunfiles());
+        Runfiles runfiles =
+            runfilesBuilder
+                .addTransitiveArtifacts(filesToBuild)
+                .addRunfiles(ruleContext, RunfilesProvider.DEFAULT_RUNFILES)
+                .build();
+
+        RuleConfiguredTargetBuilder builder = new RuleConfiguredTargetBuilder(ruleContext);
+        builder.setFilesToBuild(filesToBuild);
+        builder.add(IncompatiblePlatformProvider.class, IncompatiblePlatformProvider.simple());
+        builder.add(RunfilesProvider.class, RunfilesProvider.simple(runfiles));
+        if (outputArtifacts.size() > 0) {
+          Artifact executable = outputArtifacts.get(0);
+          RunfilesSupport runfilesSupport =
+              RunfilesSupport.withExecutable(ruleContext, runfiles, executable);
+          builder.setRunfilesSupport(runfilesSupport, executable);
+
+          ruleContext.registerAction(
+              new FailAction(
+                  ruleContext.getActionOwner(),
+                  outputArtifacts,
+                  "Can't build this. This target is incompatible."));
+        }
+        return builder.build();
+      }
+    }
+
+    // No incompatibilities found.
+    return null;
+  }
+
   private List<NestedSet<AnalysisFailure>> depAnalysisFailures(RuleContext ruleContext) {
     if (ruleContext.getConfiguration().allowAnalysisFailures()) {
       ImmutableList.Builder<NestedSet<AnalysisFailure>> analysisFailures = ImmutableList.builder();

src/main/java/com/google/devtools/build/lib/analysis/IncompatiblePlatformProvider.java

@@ -0,0 +1,29 @@
+// Copyright 2020 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 com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
+
+// TODO(phil): Document this.
+@Immutable
+public final class IncompatiblePlatformProvider implements TransitiveInfoProvider {
+  IncompatiblePlatformProvider() {
+    // Nothing to do.
+  }
+
+  public static IncompatiblePlatformProvider simple() {
+    return new IncompatiblePlatformProvider();
+  }
+}

src/main/java/com/google/devtools/build/lib/analysis/constraints/TopLevelConstraintSemantics.java

@@ -21,6 +21,7 @@
 import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.Multimap;
 import com.google.devtools.build.lib.analysis.ConfiguredTarget;
+import com.google.devtools.build.lib.analysis.IncompatiblePlatformProvider;
 import com.google.devtools.build.lib.analysis.TransitiveInfoCollection;
 import com.google.devtools.build.lib.analysis.ViewCreationFailedException;
 import com.google.devtools.build.lib.analysis.config.BuildConfiguration;
@@ -57,6 +58,19 @@ public class TopLevelConstraintSemantics {
   private final Function<Key, BuildConfiguration> configurationProvider;
   private final ExtendedEventHandler eventHandler;
 
+  // TODO(phil): Document this.
+  public class PlatformRestrictionsResult {
+    public ImmutableSet<ConfiguredTarget> targetsToSkip;
+    public ImmutableSet<ConfiguredTarget> targetsWithErrors;
+
+    public PlatformRestrictionsResult(
+        ImmutableSet<ConfiguredTarget> targetsToSkip,
+        ImmutableSet<ConfiguredTarget> targetsWithErrors) {
+      this.targetsToSkip = targetsToSkip;
+      this.targetsWithErrors = targetsWithErrors;
+    }
+  };
+
   /**
    * Constructor with helper classes for loading targets.
    *
@@ -85,6 +99,42 @@ private MissingEnvironment(Label environment, RemovedEnvironmentCulprit culprit)
     }
   }
 
+  // TODO(phil): Document this.
+  public PlatformRestrictionsResult checkPlatformRestrictions(
+      ImmutableList<ConfiguredTarget> topLevelTargets,
+      List<String> requestedTargetPatterns,
+      boolean keepGoing)
+      throws ViewCreationFailedException {
+    ImmutableSet.Builder<ConfiguredTarget> incompatibleTargets = ImmutableSet.builder();
+    ImmutableSet.Builder<ConfiguredTarget> incompatibleButRequestedTargets = ImmutableSet.builder();
+
+    for (ConfiguredTarget target : topLevelTargets) {
+      if (target.getProvider(IncompatiblePlatformProvider.class) != null) {
+        String labelString = target.getLabel().toString();
+        if (requestedTargetPatterns.contains(labelString)) {
+          if (!keepGoing) {
+            throw new ViewCreationFailedException(
+                "Target "
+                    + labelString
+                    + " is incompatible and cannot be built, but was explicitly requested.");
+          }
+          this.eventHandler.handle(
+              Event.warn(
+                  "Incompatible target "
+                      + labelString
+                      + " specifically requested: it will not be built"));
+          incompatibleButRequestedTargets.add(target);
+        } else {
+          incompatibleTargets.add(target);
+        }
+      }
+    }
+
+    return new PlatformRestrictionsResult(
+        ImmutableSet.copyOf(incompatibleTargets.build()),
+        ImmutableSet.copyOf(incompatibleButRequestedTargets.build()));
+  }
+
   /**
    * Checks that if this is an environment-restricted build, all top-level targets support expected
    * top-level environments. Expected top-level environments can be declared explicitly through

src/main/java/com/google/devtools/build/lib/buildeventstream/proto/build_event_stream.proto

@@ -543,6 +543,7 @@ enum TestStatus {
   REMOTE_FAILURE = 6;
   FAILED_TO_BUILD = 7;
   TOOL_HALTED_BEFORE_TESTING = 8;
+  SKIPPED = 9;
 }
 
 // Payload on events reporting about individual test action.

src/main/java/com/google/devtools/build/lib/buildtool/AnalysisPhaseRunner.java

@@ -213,6 +213,7 @@ private static AnalysisResult runAnalysisPhase(
             loadingResult,
             targetOptions,
             multiCpu,
+            request.getTargets(),
             request.getAspects(),
             request.getViewOptions(),
             request.getKeepGoing(),

src/main/java/com/google/devtools/build/lib/buildtool/BuildResultPrinter.java

@@ -86,16 +86,22 @@ void showBuildResult(
       if (targetsToPrint.size() > request.getBuildOptions().maxResultTargets) {
         return;
       }
-      // Filter the targets we care about into two buckets:
+      // Filter the targets we care about into three buckets:
       Collection<ConfiguredTarget> succeeded = new ArrayList<>();
       Collection<ConfiguredTarget> failed = new ArrayList<>();
+      Collection<ConfiguredTarget> skipped = new ArrayList<>();
       Collection<ConfiguredTarget> successfulTargets = result.getSuccessfulTargets();
       for (ConfiguredTarget target : targetsToPrint) {
-        (successfulTargets.contains(target) ? succeeded : failed).add(target);
+        if (configuredTargetsToSkip.contains(target)) {
+          skipped.add(target);
+        } else {
+          (successfulTargets.contains(target) ? succeeded : failed).add(target);
+        }
       }
 
-      // TODO(bazel-team): convert these to a new "SKIPPED" status when ready: b/62191890.
-      failed.addAll(configuredTargetsToSkip);
+      for (ConfiguredTarget target : skipped) {
+        outErr.printErr("Target " + target.getLabel() + " was skipped\n");
+      }
 
       TopLevelArtifactContext context = request.getTopLevelArtifactContext();
       for (ConfiguredTarget target : succeeded) {

src/main/java/com/google/devtools/build/lib/packages/RuleClass.java

@@ -264,6 +264,8 @@ public RuleErrorException(String message, Throwable cause) {
    */
   public static final String COMPATIBLE_ENVIRONMENT_ATTR = "compatible_with";
 
+  public static final String TARGET_RESTRICTED_TO_ATTR = "target_compatible_with";
+
   /**
    * For Bazel's constraint system: the implicit attribute used to store rule class restriction
    * defaults as specified by {@link Builder#restrictedTo}.
@@ -1411,6 +1413,7 @@ public <TYPE> Builder exemptFromConstraintChecking(String reason) {
       this.supportsConstraintChecking = false;
       attributes.remove(RuleClass.COMPATIBLE_ENVIRONMENT_ATTR);
       attributes.remove(RuleClass.RESTRICTED_ENVIRONMENT_ATTR);
+      attributes.remove(RuleClass.TARGET_RESTRICTED_TO_ATTR);
       return this;
     }