1 files changed, 162 insertions, 0 deletions
diff --git a/src/main/java/com/google/devtools/build/lib/rules/android/ResourceDependencies.java b/src/main/java/com/google/devtools/build/lib/rules/android/ResourceDependencies.java
new file mode 100644
index 0000000000..f55b46361a
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/rules/android/ResourceDependencies.java
@@ -0,0 +1,162 @@
+// Copyright 2015 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.android;
+
+import com.google.common.collect.Iterables;
+import com.google.devtools.build.lib.analysis.RuleConfiguredTarget.Mode;
+import com.google.devtools.build.lib.analysis.RuleContext;
+import com.google.devtools.build.lib.cmdline.Label;
+import com.google.devtools.build.lib.collect.nestedset.NestedSet;
+import com.google.devtools.build.lib.collect.nestedset.NestedSetBuilder;
+import com.google.devtools.build.lib.collect.nestedset.Order;
+import com.google.devtools.build.lib.rules.android.AndroidResourcesProvider.ResourceContainer;
+
+/**
+ * Represents a container for the {@link ResourceContainer}s for a given library. This is
+ * abstraction simplifies the process of managing and exporting the direct and transitive resource
+ * dependencies of an android rule, as well as providing type safety.
+ */
+public class ResourceDependencies {
+  /**
+   * Contains all the transitive resources that are not generated by the direct ancestors of the
+   * current rule.
+   */
+  private final NestedSet<ResourceContainer> transitiveResources;
+  /**
+   * Contains all the direct dependencies of the current target. Since a given direct dependency can
+   * act as a "forwarding" library, collecting all the direct resource from it's deps 
+   * and providing them as "direct" dependencies to maintain merge order, this uses a NestedSet to
+   * properly maintain ordering and ease of merging.
+   */
+  private final NestedSet<ResourceContainer> directResources;
+
+  public static ResourceDependencies fromRuleResources(RuleContext ruleContext) {
+
+    NestedSetBuilder<ResourceContainer> transitiveDependencies = NestedSetBuilder.naiveLinkOrder();
+    NestedSetBuilder<ResourceContainer> directDependencies = NestedSetBuilder.naiveLinkOrder();
+    extractFromAttribute("resources", ruleContext, transitiveDependencies, directDependencies);
+    return new ResourceDependencies(transitiveDependencies.build(), directDependencies.build());
+  }
+
+  public static ResourceDependencies fromRuleDeps(RuleContext ruleContext) {
+    NestedSetBuilder<ResourceContainer> transitiveDependencies = NestedSetBuilder.naiveLinkOrder();
+    NestedSetBuilder<ResourceContainer> directDependencies = NestedSetBuilder.naiveLinkOrder();
+    extractFromAttribute("deps", ruleContext, transitiveDependencies, directDependencies);
+    return new ResourceDependencies(transitiveDependencies.build(), directDependencies.build());
+  }
+
+  public static ResourceDependencies fromRuleResourceAndDeps(RuleContext ruleContext) {
+    NestedSetBuilder<ResourceContainer> transitiveDependencies = NestedSetBuilder.naiveLinkOrder();
+    NestedSetBuilder<ResourceContainer> directDependencies = NestedSetBuilder.naiveLinkOrder();
+    extractFromAttribute("resources",ruleContext, transitiveDependencies, directDependencies);
+    if (directDependencies.isEmpty()) {
+      // There are no resources, so this library will forward the direct and transitive dependencies
+      // without changes.
+      extractFromAttribute("deps", ruleContext, transitiveDependencies, directDependencies);
+    } else {
+      // There are resources, so the direct dependencies and the transitive will be merged into 
+      // the transitive dependencies. This maintains the relationship of the resources being
+      // directly on the rule.
+      extractFromAttribute("deps", ruleContext, transitiveDependencies, transitiveDependencies);
+    }
+    return new ResourceDependencies(transitiveDependencies.build(), directDependencies.build());
+  }
+
+  private static void extractFromAttribute(String attribute,
+      RuleContext ruleContext, NestedSetBuilder<ResourceContainer> builderForTransitive,
+      NestedSetBuilder<ResourceContainer> builderForDirect) {
+    for (AndroidResourcesProvider resources :
+        ruleContext.getPrerequisites(attribute, Mode.TARGET, AndroidResourcesProvider.class)) {
+      builderForTransitive.addTransitive(resources.getTransitiveAndroidResources());
+      builderForDirect.addTransitive(resources.getDirectAndroidResources());
+    }
+  }
+
+  @Override
+  public String toString() {
+    return "ResourceDependencies [transitiveResources=" + transitiveResources + ", directResources="
+        + directResources + "]";
+  }
+
+  /**
+   * Creates an empty ResourceDependencies instance. This is used when an AndroidResources rule
+   * is the only resource dependency. The most common case is the AndroidTest rule.
+   */
+  public static ResourceDependencies empty() {
+    return new ResourceDependencies(
+        NestedSetBuilder.<ResourceContainer>emptySet(Order.NAIVE_LINK_ORDER),
+        NestedSetBuilder.<ResourceContainer>emptySet(Order.NAIVE_LINK_ORDER));
+  }
+
+  public ResourceDependencies(
+      NestedSet<ResourceContainer> transitiveResources,
+      NestedSet<ResourceContainer> directResources) {
+    this.transitiveResources = transitiveResources;
+    this.directResources = directResources;
+  }
+
+  /**
+   * Creates a new AndroidResourcesProvider with the supplied ResourceContainer as the direct dep.
+   *
+   * <p>When a library produces a new resource container the AndroidResourcesProvider should use
+   * that container as a the direct dependency for that library. This makes the consuming rule
+   * to identify the new container and merge appropriately. The  previous direct dependencies are
+   * then added to the transitive dependencies.
+   *
+   * @param label The label of the library exporting this provider.
+   * @param newDirectResource The new direct dependency for AndroidResourcesProvider
+   * @return A provider with the current resources and label.
+   */
+  public AndroidResourcesProvider toProvider(Label label, ResourceContainer newDirectResource) {
+    return new AndroidResourcesProvider(
+        label,
+        NestedSetBuilder.<ResourceContainer>naiveLinkOrder()
+            .addTransitive(transitiveResources)
+            .addTransitive(directResources)
+            .build(),
+        NestedSetBuilder.<ResourceContainer>naiveLinkOrder().add(newDirectResource).build());
+  }
+
+  /**
+   * Create a new AndroidResourcesProvider from the dependencies of this library.
+   *
+   * <p>When a library doesn't export resources it should simply forward the current transitive and
+   * direct resources to the consuming rule. This allows the consuming rule to make decisions about
+   * the resource merging as if this library didn't exist.
+   *
+   * @param label The label of the library exporting this provider.
+   * @return A provider with the current resources and label.
+   */
+  public AndroidResourcesProvider toProvider(Label label) {
+    return new AndroidResourcesProvider(label, transitiveResources, directResources);
+  }
+
+  /**
+   * Provides an NestedSet of the direct and transitive resources.
+   */
+  public Iterable<ResourceContainer> getResources() {
+    return NestedSetBuilder.<ResourceContainer>naiveLinkOrder()
+        .addTransitive(directResources)
+        .addTransitive(transitiveResources)
+        .build();
+  }
+
+  public NestedSet<ResourceContainer> getTransitiveResources() {
+    return transitiveResources;
+  }
+
+  public NestedSet<ResourceContainer> getDirectResources() {
+    return directResources;
+  }
+}