Enable rules to transition based on their Rule objects.

This begins to allow for cases where a rule sets configuration
based on its attributes, such as where a rule attribute names
flags and their values - sort of a reverse select.

There are no such cases yet, but they're coming!

--
PiperOrigin-RevId: 150648357
MOS_MIGRATED_REVID=150648357

7 files changed, 220 insertions, 33 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/analysis/BuildView.java b/src/main/java/com/google/devtools/build/lib/analysis/BuildView.java
index df50202141..6043cda299 100644
--- a/src/main/java/com/google/devtools/build/lib/analysis/BuildView.java
+++ b/src/main/java/com/google/devtools/build/lib/analysis/BuildView.java
@@ -60,6 +60,7 @@ import com.google.devtools.build.lib.packages.NoSuchThingException;
 import com.google.devtools.build.lib.packages.PackageSpecification;
 import com.google.devtools.build.lib.packages.RawAttributeMapper;
 import com.google.devtools.build.lib.packages.Rule;
+import com.google.devtools.build.lib.packages.RuleTransitionFactory;
 import com.google.devtools.build.lib.packages.Target;
 import com.google.devtools.build.lib.packages.TargetUtils;
 import com.google.devtools.build.lib.pkgcache.LoadingResult;
@@ -855,11 +856,12 @@ public class BuildView {
 
       Attribute.Transition ruleclassTransition = null;
       if (targetAndConfig.getTarget().getAssociatedRule() != null) {
-        ruleclassTransition = targetAndConfig
-            .getTarget()
-            .getAssociatedRule()
-            .getRuleClassObject()
-            .getTransition();
+        Rule associatedRule = targetAndConfig.getTarget().getAssociatedRule();
+        RuleTransitionFactory transitionFactory =
+            associatedRule.getRuleClassObject().getTransitionFactory();
+        if (transitionFactory != null) {
+          ruleclassTransition = transitionFactory.buildTransitionFor(associatedRule);
+        }
       }
       if (targetAndConfig.getConfiguration() != null) {
         asDeps.put(targetAndConfig.getConfiguration(),
diff --git a/src/main/java/com/google/devtools/build/lib/analysis/config/BuildConfiguration.java b/src/main/java/com/google/devtools/build/lib/analysis/config/BuildConfiguration.java
index e7df822128..1fc05d8034 100644
--- a/src/main/java/com/google/devtools/build/lib/analysis/config/BuildConfiguration.java
+++ b/src/main/java/com/google/devtools/build/lib/analysis/config/BuildConfiguration.java
@@ -56,6 +56,7 @@ import com.google.devtools.build.lib.packages.PackageGroup;
 import com.google.devtools.build.lib.packages.Rule;
 import com.google.devtools.build.lib.packages.RuleClass;
 import com.google.devtools.build.lib.packages.RuleClassProvider;
+import com.google.devtools.build.lib.packages.RuleTransitionFactory;
 import com.google.devtools.build.lib.packages.Target;
 import com.google.devtools.build.lib.rules.test.TestActionBuilder;
 import com.google.devtools.build.lib.skylarkinterface.SkylarkCallable;
@@ -1849,15 +1850,18 @@ public final class BuildConfiguration {
       transitionsManager.configurationHook(fromRule, attribute, toTarget, this);
 
       Rule associatedRule = toTarget.getAssociatedRule();
-      PatchTransition ruleClassTransition = (PatchTransition)
-          associatedRule.getRuleClassObject().getTransition();
-
-      if (ruleClassTransition != null) {
-        if (currentTransition == ConfigurationTransition.NONE) {
-          currentTransition = ruleClassTransition;
-        } else {
-          currentTransition = new ComposingSplitTransition(ruleClassTransition,
-              currentTransition);
+      RuleTransitionFactory transitionFactory =
+          associatedRule.getRuleClassObject().getTransitionFactory();
+      if (transitionFactory != null) {
+        PatchTransition ruleClassTransition = (PatchTransition)
+            transitionFactory.buildTransitionFor(associatedRule);
+        if (ruleClassTransition != null) {
+          if (currentTransition == ConfigurationTransition.NONE) {
+            currentTransition = ruleClassTransition;
+          } else {
+            currentTransition = new ComposingSplitTransition(ruleClassTransition,
+                currentTransition);
+          }
         }
       }
 
diff --git a/src/main/java/com/google/devtools/build/lib/packages/RuleClass.java b/src/main/java/com/google/devtools/build/lib/packages/RuleClass.java
index eeacba5ad7..1a2dbb2127 100644
--- a/src/main/java/com/google/devtools/build/lib/packages/RuleClass.java
+++ b/src/main/java/com/google/devtools/build/lib/packages/RuleClass.java
@@ -445,6 +445,22 @@ public class RuleClass {
       }
     }
 
+    /**
+     * A RuleTransitionFactory which always returns the same transition.
+     */
+    private static final class FixedTransitionFactory implements RuleTransitionFactory {
+      private final Transition transition;
+
+      private FixedTransitionFactory(Transition transition) {
+        this.transition = transition;
+      }
+
+      @Override
+      public Transition buildTransitionFor(Rule rule) {
+        return transition;
+      }
+    }
+
     /** List of required attributes for normal rules, name and type. */
     public static final ImmutableList<Attribute> REQUIRED_ATTRIBUTES_FOR_NORMAL_RULES =
         ImmutableList.of(attr("tags", Type.STRING_LIST).build());
@@ -470,7 +486,7 @@ public class RuleClass {
     private boolean outputsDefaultExecutable = false;
     private ImplicitOutputsFunction implicitOutputsFunction = ImplicitOutputsFunction.NONE;
     private Configurator<?, ?> configurator = NO_CHANGE;
-    private Transition transition;
+    private RuleTransitionFactory transitionFactory;
     private ConfiguredTargetFactory<?, ?> configuredTargetFactory = null;
     private PredicateWithMessage<Rule> validityPredicate =
         PredicatesWithMessage.<Rule>alwaysTrue();
@@ -584,7 +600,7 @@ public class RuleClass {
           outputsDefaultExecutable,
           implicitOutputsFunction,
           configurator,
-          transition,
+          transitionFactory,
           configuredTargetFactory,
           validityPredicate,
           preferredDependencyPredicate,
@@ -718,8 +734,9 @@ public class RuleClass {
     public Builder cfg(Configurator<?, ?> configurator) {
       Preconditions.checkState(type != RuleClassType.ABSTRACT,
           "Setting not inherited property (cfg) of abstract rule class '%s'", name);
-      Preconditions.checkState(transition == null,
-          "Property cfg cannot be set to both a configurator and a transition");
+      Preconditions.checkState(this.transitionFactory == null && this.configurator == NO_CHANGE,
+          "Property cfg has already been set");
+      Preconditions.checkNotNull(configurator);
       this.configurator = configurator;
       return this;
     }
@@ -734,9 +751,20 @@ public class RuleClass {
     public Builder cfg(Transition transition) {
       Preconditions.checkState(type != RuleClassType.ABSTRACT,
           "Setting not inherited property (cfg) of abstract rule class '%s'", name);
-      Preconditions.checkState(configurator == NO_CHANGE,
-          "Property cfg cannot be set to both a configurator and a transition");
-      this.transition = transition;
+      Preconditions.checkState(this.transitionFactory == null && this.configurator == NO_CHANGE,
+          "Property cfg has already been set");
+      Preconditions.checkNotNull(transition);
+      this.transitionFactory = new FixedTransitionFactory(transition);
+      return this;
+    }
+
+    public Builder cfg(RuleTransitionFactory transitionFactory) {
+      Preconditions.checkState(type != RuleClassType.ABSTRACT,
+          "Setting not inherited property (cfg) of abstract rule class '%s'", name);
+      Preconditions.checkState(this.transitionFactory == null && this.configurator == NO_CHANGE,
+          "Property cfg has already been set");
+      Preconditions.checkNotNull(transitionFactory);
+      this.transitionFactory = transitionFactory;
       return this;
     }
 
@@ -1000,12 +1028,10 @@ public class RuleClass {
   private final Configurator<?, ?> configurator;
 
   /**
-   * A configuration transition that should be applied on any edge of the configured target graph
-   * that leads into a target of this rule class.
-   *
-   * <p>This transition must be a PatchTransition, but that class is not accessible in this package.
+   * A factory which will produce a configuration transition that should be applied on any edge of
+   * the configured target graph that leads into a target of this rule class.
    */
-  private final Transition transition;
+  private final RuleTransitionFactory transitionFactory;
 
   /**
    * The factory that creates configured targets from this rule.
@@ -1090,7 +1116,7 @@ public class RuleClass {
       boolean outputsDefaultExecutable,
       ImplicitOutputsFunction implicitOutputsFunction,
       Configurator<?, ?> configurator,
-      Transition transition,
+      RuleTransitionFactory transitionFactory,
       ConfiguredTargetFactory<?, ?> configuredTargetFactory,
       PredicateWithMessage<Rule> validityPredicate,
       Predicate<String> preferredDependencyPredicate,
@@ -1112,7 +1138,7 @@ public class RuleClass {
     this.binaryOutput = binaryOutput;
     this.implicitOutputsFunction = implicitOutputsFunction;
     this.configurator = Preconditions.checkNotNull(configurator);
-    this.transition = transition;
+    this.transitionFactory = transitionFactory;
     this.configuredTargetFactory = configuredTargetFactory;
     this.validityPredicate = validityPredicate;
     this.preferredDependencyPredicate = preferredDependencyPredicate;
@@ -1182,8 +1208,8 @@ public class RuleClass {
     return (Configurator<C, R>) configurator;
   }
 
-  public Transition getTransition() {
-    return transition;
+  public RuleTransitionFactory getTransitionFactory() {
+    return transitionFactory;
   }
 
   @SuppressWarnings("unchecked")
diff --git a/src/main/java/com/google/devtools/build/lib/packages/RuleTransitionFactory.java b/src/main/java/com/google/devtools/build/lib/packages/RuleTransitionFactory.java
new file mode 100644
index 0000000000..215461fa3d
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/packages/RuleTransitionFactory.java
@@ -0,0 +1,32 @@
+// 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.packages;
+
+import com.google.devtools.build.lib.packages.Attribute.Transition;
+import javax.annotation.Nullable;
+
+/**
+ * Customizable transition which accepts the rule's nonconfigurable attributes.
+ */
+public interface RuleTransitionFactory {
+  /**
+   * Generates a transition to be used when entering the given rule.
+   *
+   * <p>This transition must be a PatchTransition, but that class is not accessible in this package.
+   * If this class determines that no transition should be performed, it should return {@code null}.
+   */
+  @Nullable
+  Transition buildTransitionFor(Rule rule);
+}
diff --git a/src/test/java/com/google/devtools/build/lib/analysis/util/TestAspects.java b/src/test/java/com/google/devtools/build/lib/analysis/util/TestAspects.java
index e8bad99a60..696027c439 100644
--- a/src/test/java/com/google/devtools/build/lib/analysis/util/TestAspects.java
+++ b/src/test/java/com/google/devtools/build/lib/analysis/util/TestAspects.java
@@ -23,6 +23,7 @@ import static com.google.devtools.build.lib.syntax.Type.STRING;
 import static com.google.devtools.build.lib.syntax.Type.STRING_LIST;
 
 import com.google.common.base.Function;
+import com.google.common.base.Strings;
 import com.google.common.collect.ImmutableCollection;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableSet;
@@ -56,12 +57,15 @@ import com.google.devtools.build.lib.packages.AspectParameters;
 import com.google.devtools.build.lib.packages.Attribute.LateBoundLabel;
 import com.google.devtools.build.lib.packages.Attribute.LateBoundLabelList;
 import com.google.devtools.build.lib.packages.Attribute.SplitTransition;
+import com.google.devtools.build.lib.packages.Attribute.Transition;
 import com.google.devtools.build.lib.packages.AttributeMap;
 import com.google.devtools.build.lib.packages.BuildType;
 import com.google.devtools.build.lib.packages.NativeAspectClass;
+import com.google.devtools.build.lib.packages.NonconfigurableAttributeMapper;
 import com.google.devtools.build.lib.packages.Rule;
 import com.google.devtools.build.lib.packages.RuleClass;
 import com.google.devtools.build.lib.packages.RuleClass.Builder;
+import com.google.devtools.build.lib.packages.RuleTransitionFactory;
 import com.google.devtools.build.lib.packages.SkylarkProviderIdentifier;
 import com.google.devtools.build.lib.rules.RuleConfiguredTargetFactory;
 import com.google.devtools.build.lib.syntax.Type;
@@ -1040,6 +1044,65 @@ public class TestAspects {
     }
   }
 
+  private static class SetsTestFilterFromAttributePatchTransition implements PatchTransition {
+    private final String value;
+
+    public SetsTestFilterFromAttributePatchTransition(String value) {
+      this.value = value;
+    }
+
+    @Override
+    public BuildOptions apply(BuildOptions options) {
+      BuildOptions result = options.clone();
+      result.get(Options.class).testFilter = "SET BY PATCH FACTORY: " + value;
+      return result;
+    }
+
+    @Override
+    public boolean defaultsToSelf() {
+      return true;
+    }
+  }
+
+  private static class SetsTestFilterFromAttributeTransitionFactory
+      implements RuleTransitionFactory {
+    @Override
+    public Transition buildTransitionFor(Rule rule) {
+      NonconfigurableAttributeMapper attributes = NonconfigurableAttributeMapper.of(rule);
+      String value = attributes.get("sets_test_filter_to", STRING);
+      if (Strings.isNullOrEmpty(value)) {
+        return null;
+      } else {
+        return new SetsTestFilterFromAttributePatchTransition(value);
+      }
+    }
+  }
+
+  /**
+   * Rule with a RuleTransitionFactory which sets the --test_filter flag according to its attribute.
+   */
+  public static class UsesRuleTransitionFactoryRule implements RuleDefinition {
+    @Override
+    public RuleClass build(Builder builder, RuleDefinitionEnvironment environment) {
+      return builder
+          .cfg(new SetsTestFilterFromAttributeTransitionFactory())
+          .add(
+              attr("sets_test_filter_to", STRING)
+                  .nonconfigurable("used in RuleTransitionFactory")
+                  .value(""))
+          .build();
+    }
+
+    @Override
+    public Metadata getMetadata() {
+      return RuleDefinition.Metadata.builder()
+          .name("uses_rule_transition_factory")
+          .factoryClass(DummyRuleFactory.class)
+          .ancestors(BaseRule.class)
+          .build();
+    }
+  }
+
   /** A rule with an empty split transition on an attribute. */
   public static class EmptySplitRule implements RuleDefinition {
     @Override
diff --git a/src/test/java/com/google/devtools/build/lib/packages/RuleClassTest.java b/src/test/java/com/google/devtools/build/lib/packages/RuleClassTest.java
index 39e9523cf4..08c86ee6b7 100644
--- a/src/test/java/com/google/devtools/build/lib/packages/RuleClassTest.java
+++ b/src/test/java/com/google/devtools/build/lib/packages/RuleClassTest.java
@@ -49,7 +49,6 @@ import com.google.devtools.build.lib.events.EventKind;
 import com.google.devtools.build.lib.events.Location;
 import com.google.devtools.build.lib.events.Location.LineAndColumn;
 import com.google.devtools.build.lib.packages.Attribute.SkylarkComputedDefaultTemplate.CannotPrecomputeDefaultsException;
-import com.google.devtools.build.lib.packages.Attribute.Transition;
 import com.google.devtools.build.lib.packages.Attribute.ValidityPredicate;
 import com.google.devtools.build.lib.packages.ConfigurationFragmentPolicy.MissingFragmentPolicy;
 import com.google.devtools.build.lib.packages.RuleClass.Builder.RuleClassType;
@@ -861,7 +860,7 @@ public class RuleClassTest extends PackageLoadingTestCase {
       boolean outputsDefaultExecutable,
       ImplicitOutputsFunction implicitOutputsFunction,
       Configurator<?, ?> configurator,
-      Transition transition,
+      RuleTransitionFactory transitionFactory,
       ConfiguredTargetFactory<?, ?> configuredTargetFactory,
       PredicateWithMessage<Rule> validityPredicate,
       Predicate<String> preferredDependencyPredicate,
@@ -889,7 +888,7 @@ public class RuleClassTest extends PackageLoadingTestCase {
         outputsDefaultExecutable,
         implicitOutputsFunction,
         configurator,
-        transition,
+        transitionFactory,
         configuredTargetFactory,
         validityPredicate,
         preferredDependencyPredicate,
diff --git a/src/test/java/com/google/devtools/build/lib/skyframe/ConfigurationsForTargetsWithDynamicConfigurationsTest.java b/src/test/java/com/google/devtools/build/lib/skyframe/ConfigurationsForTargetsWithDynamicConfigurationsTest.java
index 43a4b435b8..a587ebaf01 100644
--- a/src/test/java/com/google/devtools/build/lib/skyframe/ConfigurationsForTargetsWithDynamicConfigurationsTest.java
+++ b/src/test/java/com/google/devtools/build/lib/skyframe/ConfigurationsForTargetsWithDynamicConfigurationsTest.java
@@ -148,6 +148,67 @@ public class ConfigurationsForTargetsWithDynamicConfigurationsTest
     assertThat(target.getConfiguration().getCpu()).isNotEqualTo("SET BY PATCH");
   }
 
+  @Test
+  public void ruleTransitionFactoryUsesNonconfigurableAttributesToGenerateTransition()
+      throws Exception {
+    setRulesAvailableInTests(
+        new TestAspects.BaseRule(),
+        new TestAspects.AttributeTransitionRule(),
+        new TestAspects.UsesRuleTransitionFactoryRule());
+    useConfiguration("--test_filter=SET ON COMMAND LINE: original and best");
+    scratch.file(
+        "a/BUILD",
+        "attribute_transition(",
+        "   name='top',",
+        "   without_transition=':factory',",
+        ")",
+        "uses_rule_transition_factory(",
+        "   name='factory',",
+        "   sets_test_filter_to='funkiest',",
+        ")");
+    List<ConfiguredTarget> deps = getConfiguredDeps("//a:top", "without_transition");
+    BuildConfiguration config = Iterables.getOnlyElement(deps).getConfiguration();
+    assertThat(config.getTestFilter()).isEqualTo("SET BY PATCH FACTORY: funkiest");
+  }
+
+  @Test
+  public void ruleTransitionFactoryCanReturnNullToCauseNoTransition() throws Exception {
+    setRulesAvailableInTests(
+        new TestAspects.BaseRule(),
+        new TestAspects.AttributeTransitionRule(),
+        new TestAspects.UsesRuleTransitionFactoryRule());
+    useConfiguration("--test_filter=SET ON COMMAND LINE: original and best");
+    scratch.file(
+        "a/BUILD",
+        "attribute_transition(",
+        "   name='top',",
+        "   without_transition=':factory',",
+        ")",
+        "uses_rule_transition_factory(",
+        "   name='factory',",
+        "   sets_test_filter_to='',",
+        ")");
+    List<ConfiguredTarget> deps = getConfiguredDeps("//a:top", "without_transition");
+    BuildConfiguration config = Iterables.getOnlyElement(deps).getConfiguration();
+    assertThat(config.getTestFilter()).isEqualTo("SET ON COMMAND LINE: original and best");
+  }
+
+  @Test
+  public void topLevelRuleTransitionFactoryUsesNonconfigurableAttributes() throws Exception {
+    setRulesAvailableInTests(
+        new TestAspects.BaseRule(), new TestAspects.UsesRuleTransitionFactoryRule());
+    useConfiguration("--test_filter=SET ON COMMAND LINE: original and best");
+    scratch.file(
+        "a/BUILD",
+        "uses_rule_transition_factory(",
+        "   name='factory',",
+        "   sets_test_filter_to='Maximum Dance',",
+        ")");
+    ConfiguredTarget target = Iterables.getOnlyElement(update("//a:factory").getTargetsToBuild());
+    assertThat(target.getConfiguration().getTestFilter())
+        .isEqualTo("SET BY PATCH FACTORY: Maximum Dance");
+  }
+
   /**
    * Returns a custom {@link PatchTransition} with the given value added to
    * {@link BuildConfiguration.Options#testFilter}.