2 files changed, 32 insertions, 2 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/rules/objc/ObjcProtoLibraryRule.java b/src/main/java/com/google/devtools/build/lib/rules/objc/ObjcProtoLibraryRule.java
index cf2bbcd00c..2e6f741b7f 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/objc/ObjcProtoLibraryRule.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/objc/ObjcProtoLibraryRule.java
@@ -46,6 +46,7 @@ public class ObjcProtoLibraryRule implements RuleDefinition {
   static final String PROTO_COMPILER_ATTR = "$googlemac_proto_compiler";
   static final String PROTO_COMPILER_SUPPORT_ATTR = "$googlemac_proto_compiler_support";
   static final String PROTO_LIB_ATTR = "$lib_protobuf";
+  static final String PROTOBUF_WELL_KNOWN_TYPES = "$protobuf_well_known_types";
   static final String XCODE_GEN_ATTR = "$xcodegen";
 
   @Override
@@ -131,6 +132,17 @@ public class ObjcProtoLibraryRule implements RuleDefinition {
                       }
                     }))
         .add(
+            // The well known type proto label should resolve to the shared location of proto
+            // dependencies of targets in the workspace. Unless all dependencies refer to the same
+            // label for these proto dependencies, an artifact comparison between them is not
+            // possible. Ultimately, we will need to resolve this cross-repository dependency, but,
+            // for now, these well-known protos do not exist in a common repository, and must thus
+            // be present in the root workspace.
+            attr(PROTOBUF_WELL_KNOWN_TYPES, LABEL)
+                .cfg(HOST)
+                .exec()
+                .value(env.getLabel("//tools/objc:protobuf_well_known_types")))
+        .add(
             attr(XCODE_GEN_ATTR, LABEL)
                 .cfg(HOST)
                 .exec()
diff --git a/src/main/java/com/google/devtools/build/lib/rules/objc/ProtoSupport.java b/src/main/java/com/google/devtools/build/lib/rules/objc/ProtoSupport.java
index 6d0a6a3fec..008cae937b 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/objc/ProtoSupport.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/objc/ProtoSupport.java
@@ -20,6 +20,7 @@ import static com.google.common.base.CaseFormat.UPPER_CAMEL;
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Function;
 import com.google.common.base.Optional;
+import com.google.common.base.Predicates;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.Iterables;
@@ -262,7 +263,7 @@ final class ProtoSupport {
   }
 
   private String getProtoInputListFileContents() {
-    return Artifact.joinExecPaths("\n", attributes.getProtoFiles());
+    return Artifact.joinExecPaths("\n", getFilteredProtos());
   }
 
   private NestedSet<Artifact> getGenerateActionInputs() {
@@ -351,7 +352,7 @@ final class ProtoSupport {
 
   private ImmutableList<Artifact> generatedOutputArtifacts(FileType newFileType) {
     ImmutableList.Builder<Artifact> builder = new ImmutableList.Builder<>();
-    for (Artifact protoFile : attributes.getProtoFiles()) {
+    for (Artifact protoFile : getFilteredProtos()) {
       String generatedOutputName;
       if (attributes.outputsCpp()) {
         generatedOutputName = protoFile.getFilename();
@@ -378,6 +379,14 @@ final class ProtoSupport {
     return builder.build();
   }
 
+  private Iterable<Artifact> getFilteredProtos() {
+    // Filter the well known types from being sent to be generated, as these protos have already
+    // been generated and linked in libprotobuf.a.
+    return Iterables.filter(
+        attributes.getProtoFiles(),
+        Predicates.not(Predicates.in(attributes.getWellKnownTypeProtos())));
+  }
+
   /**
    * Common rule attributes used by an Objective C proto library.
    */
@@ -432,6 +441,15 @@ final class ProtoSupport {
     }
 
     /**
+     * Returns the list of well known type protos.
+     */
+    ImmutableList<Artifact> getWellKnownTypeProtos() {
+      return ruleContext
+          .getPrerequisiteArtifacts(ObjcProtoLibraryRule.PROTOBUF_WELL_KNOWN_TYPES, Mode.HOST)
+          .list();
+    }
+
+    /**
      * Returns the options file, or null if it was not specified.
      */
     @Nullable