1 files changed, 75 insertions, 0 deletions
diff --git a/src/main/java/com/google/devtools/build/lib/rules/config/ConfigFeatureFlagTransitionFactory.java b/src/main/java/com/google/devtools/build/lib/rules/config/ConfigFeatureFlagTransitionFactory.java
new file mode 100644
index 0000000000..8f7ab87954
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/rules/config/ConfigFeatureFlagTransitionFactory.java
@@ -0,0 +1,75 @@
+// 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.rules.config;
+
+import static com.google.devtools.build.lib.packages.BuildType.LABEL_KEYED_STRING_DICT;
+
+import com.google.common.collect.ImmutableSortedMap;
+import com.google.devtools.build.lib.analysis.config.BuildOptions;
+import com.google.devtools.build.lib.analysis.config.PatchTransition;
+import com.google.devtools.build.lib.cmdline.Label;
+import com.google.devtools.build.lib.packages.NonconfigurableAttributeMapper;
+import com.google.devtools.build.lib.packages.Rule;
+import com.google.devtools.build.lib.packages.RuleTransitionFactory;
+import java.util.Map;
+
+/**
+ * Transition factory which allows for setting the values of config_feature_flags below the rule
+ * it is attached to based on one of that rule's attributes.
+ *
+ * <p>Currently, this is only intended for use by android_binary and other Android top-level rules.
+ */
+public class ConfigFeatureFlagTransitionFactory implements RuleTransitionFactory {
+
+  /** Transition which resets the set of flag-value pairs to the map it was constructed with. */
+  private static final class ConfigFeatureFlagValuesTransition implements PatchTransition {
+    private final ImmutableSortedMap<Label, String> flagValues;
+
+    public ConfigFeatureFlagValuesTransition(Map<Label, String> flagValues) {
+      this.flagValues = ImmutableSortedMap.copyOf(flagValues);
+    }
+
+    @Override
+    public BuildOptions apply(BuildOptions options) {
+      BuildOptions result = options.clone();
+      result.get(ConfigFeatureFlagConfiguration.Options.class).replaceFlagValues(flagValues);
+      return result;
+    }
+
+    @Override
+    public boolean defaultsToSelf() {
+      throw new UnsupportedOperationException("supported in dynamic mode only");
+    }
+  }
+
+  private final String attributeName;
+
+  /**
+   * Creates a transition factory which will generate a transition over a given rule which sets
+   * exactly the flag values in the attribute with the given {@code attributeName} of that rule,
+   * unsetting any flag values not listed there.
+   *
+   * <p>This attribute must be a nonconfigurable {@code LABEL_KEYED_STRING_DICT}.
+   */
+  public ConfigFeatureFlagTransitionFactory(String attributeName) {
+    this.attributeName = attributeName;
+  }
+
+  @Override
+  public PatchTransition buildTransitionFor(Rule rule) {
+    return new ConfigFeatureFlagValuesTransition(
+        NonconfigurableAttributeMapper.of(rule).get(attributeName, LABEL_KEYED_STRING_DICT));
+  }
+}