Add flag to turn Android resource merge conflicts from warnings into errors

RELNOTES: none
PiperOrigin-RevId: 161831232

13 files changed, 248 insertions, 65 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/rules/android/AarGeneratorBuilder.java b/src/main/java/com/google/devtools/build/lib/rules/android/AarGeneratorBuilder.java
index b0ffa9e5b5..c311d82f0f 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/android/AarGeneratorBuilder.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/android/AarGeneratorBuilder.java
@@ -40,6 +40,7 @@ public class AarGeneratorBuilder {
   private Artifact classes;
 
   private Artifact aarOut;
+  private boolean throwOnResourceConflict;
 
   private final RuleContext ruleContext;
   private final SpawnAction.Builder builder;
@@ -79,6 +80,11 @@ public class AarGeneratorBuilder {
     return this;
   }
 
+  public AarGeneratorBuilder setThrowOnResourceConflict(boolean throwOnResourceConflict) {
+    this.throwOnResourceConflict = throwOnResourceConflict;
+    return this;
+  }
+
   public void build(ActionConstructionContext context) {
     List<Artifact> outs = new ArrayList<>();
     List<Artifact> ins = new ArrayList<>();
@@ -115,6 +121,10 @@ public class AarGeneratorBuilder {
     args.add(aarOut.getExecPathString());
     outs.add(aarOut);
 
+    if (throwOnResourceConflict) {
+      args.add("--throwOnResourceConflict");
+    }
+
     ruleContext.registerAction(
         this.builder
             .addInputs(ImmutableList.<Artifact>copyOf(ins))
diff --git a/src/main/java/com/google/devtools/build/lib/rules/android/AndroidConfiguration.java b/src/main/java/com/google/devtools/build/lib/rules/android/AndroidConfiguration.java
index 4820e03710..03878f5bfe 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/android/AndroidConfiguration.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/android/AndroidConfiguration.java
@@ -648,6 +648,15 @@ public class AndroidConfiguration extends BuildConfiguration.Fragment {
     )
     public boolean generateRobolectricRClass;
 
+    @Option(
+        name = "experimental_android_throw_on_resource_conflict",
+        defaultValue = "false",
+        documentationCategory = OptionDocumentationCategory.UNCATEGORIZED,
+        effectTags = {OptionEffectTag.UNKNOWN},
+        help = "If passed, resource merge conflicts will be treated as errors instead of warnings"
+    )
+    public boolean throwOnResourceConflict;
+
     @Override
     public FragmentOptions getHost(boolean fallback) {
       Options host = (Options) super.getHost(fallback);
@@ -725,6 +734,7 @@ public class AndroidConfiguration extends BuildConfiguration.Fragment {
   private final boolean exportsManifestDefault;
   private final AndroidAaptVersion androidAaptVersion;
   private final boolean generateRobolectricRClass;
+  private final boolean throwOnResourceConflict;
   private final boolean useParallelDex2Oat;
 
   AndroidConfiguration(Options options) throws InvalidConfigurationException {
@@ -760,6 +770,7 @@ public class AndroidConfiguration extends BuildConfiguration.Fragment {
     this.exportsManifestDefault = options.exportsManifestDefault;
     this.androidAaptVersion = options.androidAaptVersion;
     this.generateRobolectricRClass = options.generateRobolectricRClass;
+    this.throwOnResourceConflict = options.throwOnResourceConflict;
     this.useParallelDex2Oat = options.useParallelDex2Oat;
 
     if (!dexoptsSupportedInIncrementalDexing.contains("--no-locals")) {
@@ -889,6 +900,10 @@ public class AndroidConfiguration extends BuildConfiguration.Fragment {
     return generateRobolectricRClass;
   }
 
+  boolean throwOnResourceConflict() {
+    return throwOnResourceConflict;
+  }
+
   @Override
   public void addGlobalMakeVariables(ImmutableMap.Builder<String, String> globalMakeEnvBuilder) {
     globalMakeEnvBuilder.put("ANDROID_CPU", cpu);
diff --git a/src/main/java/com/google/devtools/build/lib/rules/android/AndroidLibrary.java b/src/main/java/com/google/devtools/build/lib/rules/android/AndroidLibrary.java
index 98fcb45946..83cc88ec6c 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/android/AndroidLibrary.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/android/AndroidLibrary.java
@@ -180,6 +180,8 @@ public abstract class AndroidLibrary implements RuleConfiguredTargetFactory {
           .withPrimary(resourceContainer)
           .withDependencies(resourceApk.getResourceDependencies())
           .setDebug(ruleContext.getConfiguration().getCompilationMode() != CompilationMode.OPT)
+          .setThrowOnResourceConflict(
+              ruleContext.getFragment(AndroidConfiguration.class).throwOnResourceConflict())
           .build(ruleContext);
     }
 
@@ -189,6 +191,8 @@ public abstract class AndroidLibrary implements RuleConfiguredTargetFactory {
       .withRtxt(primaryResources.getRTxt())
       .withClasses(classesJar)
       .setAAROut(aarOut)
+      .setThrowOnResourceConflict(
+          ruleContext.getFragment(AndroidConfiguration.class).throwOnResourceConflict())
       .build(ruleContext);
 
     RuleConfiguredTargetBuilder builder = new RuleConfiguredTargetBuilder(ruleContext);
diff --git a/src/main/java/com/google/devtools/build/lib/rules/android/AndroidResourceMergingActionBuilder.java b/src/main/java/com/google/devtools/build/lib/rules/android/AndroidResourceMergingActionBuilder.java
index e86cae2441..5b63f24af6 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/android/AndroidResourceMergingActionBuilder.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/android/AndroidResourceMergingActionBuilder.java
@@ -65,6 +65,7 @@ public class AndroidResourceMergingActionBuilder {
 
   // Flags
   private String customJavaPackage;
+  private boolean throwOnResourceConflict;
 
   /** @param ruleContext The RuleContext that was used to create the SpawnAction.Builder. */
   public AndroidResourceMergingActionBuilder(RuleContext ruleContext) {
@@ -116,6 +117,12 @@ public class AndroidResourceMergingActionBuilder {
     return this;
   }
 
+  public AndroidResourceMergingActionBuilder setThrowOnResourceConflict(
+      boolean throwOnResourceConflict) {
+    this.throwOnResourceConflict = throwOnResourceConflict;
+    return this;
+  }
+
   public ResourceContainer build(ActionConstructionContext context) {
     CustomCommandLine.Builder builder = new CustomCommandLine.Builder();
 
@@ -170,6 +177,10 @@ public class AndroidResourceMergingActionBuilder {
       outs.add(dataBindingInfoZip);
     }
 
+    if (throwOnResourceConflict) {
+      builder.add("--throwOnResourceConflict");
+    }
+
     SpawnAction.Builder spawnActionBuilder = new SpawnAction.Builder();
     // Create the spawn action.
     ruleContext.registerAction(
diff --git a/src/main/java/com/google/devtools/build/lib/rules/android/AndroidResourcesProcessorBuilder.java b/src/main/java/com/google/devtools/build/lib/rules/android/AndroidResourcesProcessorBuilder.java
index b61bee6269..fd827b6962 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/android/AndroidResourcesProcessorBuilder.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/android/AndroidResourcesProcessorBuilder.java
@@ -110,6 +110,7 @@ public class AndroidResourcesProcessorBuilder {
   private Artifact featureOf;
   private Artifact featureAfter;
   private AndroidAaptVersion aaptVersion;
+  private boolean throwOnResourceConflict;
 
   /**
    * @param ruleContext The RuleContext that was used to create the SpawnAction.Builder.
@@ -232,6 +233,12 @@ public class AndroidResourcesProcessorBuilder {
     return this;
   }
 
+  public AndroidResourcesProcessorBuilder setThrowOnResourceConflict(
+      boolean throwOnResourceConflict) {
+    this.throwOnResourceConflict = throwOnResourceConflict;
+    return this;
+  }
+
   public ResourceContainer build(ActionConstructionContext context) {
     if (aaptVersion == AndroidAaptVersion.AAPT2) {
       return createAapt2ApkAction(context);
@@ -467,5 +474,9 @@ public class AndroidResourcesProcessorBuilder {
       builder.addExecPath("--featureAfter", featureAfter);
       inputs.add(featureAfter);
     }
+
+    if (throwOnResourceConflict) {
+      builder.add("--throwOnResourceConflict");
+    }
   }
 }
diff --git a/src/main/java/com/google/devtools/build/lib/rules/android/ApplicationManifest.java b/src/main/java/com/google/devtools/build/lib/rules/android/ApplicationManifest.java
index a9d096ee2a..1ef2406f50 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/android/ApplicationManifest.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/android/ApplicationManifest.java
@@ -603,7 +603,10 @@ public final class ApplicationManifest {
               .setMergedResourcesOut(mergedResources)
               .setManifestOut(manifestOut)
               .setClassJarOut(rJavaClassJar)
-              .setDataBindingInfoZip(dataBindingInfoZip);
+              .setDataBindingInfoZip(dataBindingInfoZip)
+              .setThrowOnResourceConflict(
+                  ruleContext.getConfiguration()
+                      .getFragment(AndroidConfiguration.class).throwOnResourceConflict());
       ResourceContainer merged = resourcesMergerBuilder.build(ruleContext);
 
       processed =
@@ -642,7 +645,10 @@ public final class ApplicationManifest {
               .setVersionCode(manifestValues.get("versionCode"))
               .setVersionName(manifestValues.get("versionName"))
               .setFeatureOf(featureOf)
-              .setFeatureAfter(featureAfter);
+              .setFeatureAfter(featureAfter)
+              .setThrowOnResourceConflict(
+                ruleContext.getConfiguration()
+                    .getFragment(AndroidConfiguration.class).throwOnResourceConflict());
       if (!incremental) {
         builder
             .targetAaptVersion(AndroidAaptVersion.AAPT)
diff --git a/src/test/java/com/google/devtools/build/android/AndroidDataMergerTest.java b/src/test/java/com/google/devtools/build/android/AndroidDataMergerTest.java
index 1444b83fd6..e28d65ceb3 100644
--- a/src/test/java/com/google/devtools/build/android/AndroidDataMergerTest.java
+++ b/src/test/java/com/google/devtools/build/android/AndroidDataMergerTest.java
@@ -25,6 +25,7 @@ import com.google.common.jimfs.Jimfs;
 import com.google.common.truth.FailureStrategy;
 import com.google.common.truth.SubjectFactory;
 import com.google.devtools.build.android.AndroidDataBuilder.ResourceType;
+import com.google.devtools.build.android.AndroidDataMerger.MergeConflictException;
 import com.google.devtools.build.android.AndroidDataMerger.SourceChecker;
 import com.google.devtools.build.android.xml.IdXmlResourceValue;
 import com.google.devtools.build.android.xml.PublicXmlResourceValue;
@@ -102,7 +103,7 @@ public class AndroidDataMergerTest {
     AndroidDataMerger merger = AndroidDataMerger.createWithDefaults();
 
     UnwrittenMergedAndroidData data =
-        merger.merge(transitiveDependency, directDependency, primary, false);
+        merger.merge(transitiveDependency, directDependency, primary, false, true);
 
     UnwrittenMergedAndroidData expected =
         UnwrittenMergedAndroidData.of(
@@ -161,7 +162,7 @@ public class AndroidDataMergerTest {
     AndroidDataMerger merger = AndroidDataMerger.createWithDefaults();
 
     UnwrittenMergedAndroidData data =
-        merger.merge(transitiveDependency, directDependency, primary, false);
+        merger.merge(transitiveDependency, directDependency, primary, false, true);
 
     UnwrittenMergedAndroidData expected =
         UnwrittenMergedAndroidData.of(
@@ -226,7 +227,7 @@ public class AndroidDataMergerTest {
     AndroidDataMerger merger = AndroidDataMerger.createWithDefaults();
 
     UnwrittenMergedAndroidData transitive =
-        merger.merge(transitiveDependency, directDependency, primary, false);
+        merger.merge(transitiveDependency, directDependency, primary, false, true);
 
     UnwrittenMergedAndroidData expected =
         UnwrittenMergedAndroidData.of(
@@ -276,7 +277,7 @@ public class AndroidDataMergerTest {
 
     AndroidDataMerger merger = AndroidDataMerger.createWithDefaults();
 
-    merger.merge(transitiveDependency, directDependency, primary, false);
+    merger.merge(transitiveDependency, directDependency, primary, false, false);
 
     assertThat(loggingHandler.warnings)
         .containsExactly(
@@ -325,7 +326,7 @@ public class AndroidDataMergerTest {
             });
 
     assertAbout(unwrittenMergedAndroidData)
-        .that(merger.merge(transitiveDependency, directDependency, primary, false))
+        .that(merger.merge(transitiveDependency, directDependency, primary, false, true))
         .isEqualTo(
             UnwrittenMergedAndroidData.of(
                 primary.getManifest(),
@@ -367,7 +368,7 @@ public class AndroidDataMergerTest {
             .buildUnvalidated();
 
     AndroidDataMerger merger = AndroidDataMerger.createWithDefaults();
-    merger.merge(transitiveDependency, directDependency, primary, false);
+    merger.merge(transitiveDependency, directDependency, primary, false, true);
 
     assertThat(loggingHandler.warnings).isEmpty();
   }
@@ -402,7 +403,7 @@ public class AndroidDataMergerTest {
 
     AndroidDataMerger merger = AndroidDataMerger.createWithDefaults();
     UnwrittenMergedAndroidData data =
-        merger.merge(transitiveDependency, directDependency, primary, true);
+        merger.merge(transitiveDependency, directDependency, primary, true, true);
     UnwrittenMergedAndroidData expected =
         UnwrittenMergedAndroidData.of(
             primary.getManifest(),
@@ -442,7 +443,7 @@ public class AndroidDataMergerTest {
 
     AndroidDataMerger merger = AndroidDataMerger.createWithDefaults();
 
-    merger.merge(transitiveDependency, directDependency, primary, false);
+    merger.merge(transitiveDependency, directDependency, primary, false, false);
 
     assertThat(loggingHandler.warnings)
         .containsExactly(
@@ -489,7 +490,7 @@ public class AndroidDataMergerTest {
 
     AndroidDataMerger merger = AndroidDataMerger.createWithDefaults();
     UnwrittenMergedAndroidData data =
-        merger.merge(transitiveDependency, directDependency, primary, true);
+        merger.merge(transitiveDependency, directDependency, primary, true, true);
     UnwrittenMergedAndroidData expected =
         UnwrittenMergedAndroidData.of(
             primary.getManifest(),
@@ -533,7 +534,7 @@ public class AndroidDataMergerTest {
 
     AndroidDataMerger merger = AndroidDataMerger.createWithDefaults();
 
-    merger.merge(transitiveDependency, directDependency, primary, false);
+    merger.merge(transitiveDependency, directDependency, primary, false, false);
     assertThat(loggingHandler.warnings)
         .containsExactly(
             MergeConflict.of(
@@ -578,23 +579,62 @@ public class AndroidDataMergerTest {
 
     AndroidDataMerger merger = AndroidDataMerger.createWithDefaults();
 
-    merger.merge(transitiveDependency, directDependency, primary, false);
+    merger.merge(transitiveDependency, directDependency, primary, false, false);
 
     FullyQualifiedName fullyQualifiedName = fqnFactory.parse("string/exit");
     assertThat(loggingHandler.warnings)
         .containsExactly(
             MergeConflict.of(
-                    fullyQualifiedName,
-                    DataResourceXml.createWithNoNamespace(
-                        directRoot.resolve("res/values/strings.xml"),
-                        SimpleXmlResourceValue.createWithValue(Type.STRING, "no way out")),
-                    DataResourceXml.createWithNoNamespace(
-                        transitiveRoot.resolve("res/values/strings.xml"),
-                        SimpleXmlResourceValue.createWithValue(Type.STRING, "wrong way out")))
+                fullyQualifiedName,
+                DataResourceXml.createWithNoNamespace(
+                    directRoot.resolve("res/values/strings.xml"),
+                    SimpleXmlResourceValue.createWithValue(Type.STRING, "no way out")),
+                DataResourceXml.createWithNoNamespace(
+                    transitiveRoot.resolve("res/values/strings.xml"),
+                    SimpleXmlResourceValue.createWithValue(Type.STRING, "wrong way out")))
                 .toConflictMessage());
   }
 
   @Test
+  public void mergeDirectTransitivePrimaryConflictWithThrowOnConflict() throws Exception {
+    Path primaryRoot = fileSystem.getPath("primary");
+    Path directRoot = fileSystem.getPath("direct");
+    Path transitiveRoot = fileSystem.getPath("transitive");
+
+    ParsedAndroidData transitiveDependency =
+        ParsedAndroidDataBuilder.buildOn(transitiveRoot, fqnFactory)
+            .overwritable(
+                xml("string/exit")
+                    .source("values/strings.xml")
+                    .value(SimpleXmlResourceValue.createWithValue(Type.STRING, "no way out")))
+            .build();
+
+    ParsedAndroidData directDependency =
+        ParsedAndroidDataBuilder.buildOn(directRoot, fqnFactory)
+            .overwritable(
+                xml("string/exit")
+                    .source("values/strings.xml")
+                    .value(SimpleXmlResourceValue.createWithValue(Type.STRING, "wrong way out")))
+            .build();
+
+    UnvalidatedAndroidData primary =
+        AndroidDataBuilder.of(primaryRoot)
+            .createManifest("AndroidManifest.xml", "com.google.mergetest")
+            .addResource(
+                "values/strings.xml", ResourceType.VALUE, "<string name='exit'>way out</string>")
+            .buildUnvalidated();
+
+    AndroidDataMerger merger = AndroidDataMerger.createWithDefaults();
+
+    try {
+      merger.merge(transitiveDependency, directDependency, primary, false, true);
+      throw new Exception("Expected a MergeConflictException!");
+    } catch (MergeConflictException e) {
+      return;
+    }
+  }
+
+  @Test
   public void mergeDirectTransitivePrimaryConflictWithPrimaryOverride() throws Exception {
     Path primaryRoot = fileSystem.getPath("primary");
     Path directRoot = fileSystem.getPath("direct");
@@ -629,7 +669,7 @@ public class AndroidDataMergerTest {
 
     UnwrittenMergedAndroidData data =
         AndroidDataMerger.createWithDefaults()
-            .merge(transitiveDependency, directDependency, primary, true);
+            .merge(transitiveDependency, directDependency, primary, true, true);
 
     UnwrittenMergedAndroidData expected =
         UnwrittenMergedAndroidData.of(
@@ -667,7 +707,7 @@ public class AndroidDataMergerTest {
             .buildUnvalidated();
 
     AndroidDataMerger merger = AndroidDataMerger.createWithDefaults();
-    merger.merge(transitiveDependency, directDependency, primary, false);
+    merger.merge(transitiveDependency, directDependency, primary, false, false);
 
     assertThat(loggingHandler.warnings)
         .containsExactly(
@@ -699,7 +739,7 @@ public class AndroidDataMergerTest {
     AndroidDataMerger merger = AndroidDataMerger.createWithDefaults();
 
     UnwrittenMergedAndroidData data =
-        merger.merge(transitiveDependency, directDependency, primary, false);
+        merger.merge(transitiveDependency, directDependency, primary, false, true);
 
     UnwrittenMergedAndroidData expected =
         UnwrittenMergedAndroidData.of(
@@ -753,7 +793,7 @@ public class AndroidDataMergerTest {
     AndroidDataMerger merger = AndroidDataMerger.createWithDefaults();
 
     UnwrittenMergedAndroidData data =
-        merger.merge(transitiveDependency, directDependency, primary, false);
+        merger.merge(transitiveDependency, directDependency, primary, false, true);
 
     UnwrittenMergedAndroidData expected =
         UnwrittenMergedAndroidData.of(
@@ -816,7 +856,7 @@ public class AndroidDataMergerTest {
     AndroidDataMerger merger = AndroidDataMerger.createWithDefaults();
 
     UnwrittenMergedAndroidData data =
-        merger.merge(transitiveDependency, directDependency, primary, false);
+        merger.merge(transitiveDependency, directDependency, primary, false, true);
 
     UnwrittenMergedAndroidData expected =
         UnwrittenMergedAndroidData.of(
@@ -885,7 +925,7 @@ public class AndroidDataMergerTest {
     AndroidDataMerger merger = AndroidDataMerger.createWithDefaults();
 
     UnwrittenMergedAndroidData data =
-        merger.merge(transitiveDependency, directDependency, primary, false);
+        merger.merge(transitiveDependency, directDependency, primary, false, true);
 
     UnwrittenMergedAndroidData expected =
         UnwrittenMergedAndroidData.of(
@@ -948,7 +988,7 @@ public class AndroidDataMergerTest {
     AndroidDataMerger merger = AndroidDataMerger.createWithDefaults();
 
     UnwrittenMergedAndroidData data =
-        merger.merge(transitiveDependency, directDependency, primary, false);
+        merger.merge(transitiveDependency, directDependency, primary, false, true);
 
     UnwrittenMergedAndroidData expected =
         UnwrittenMergedAndroidData.of(
@@ -996,7 +1036,7 @@ public class AndroidDataMergerTest {
     AndroidDataMerger merger = AndroidDataMerger.createWithDefaults();
 
     UnwrittenMergedAndroidData data =
-        merger.merge(transitiveDependency, directDependency, primary, false);
+        merger.merge(transitiveDependency, directDependency, primary, false, true);
 
     UnwrittenMergedAndroidData expected =
         UnwrittenMergedAndroidData.of(
@@ -1034,7 +1074,7 @@ public class AndroidDataMergerTest {
 
     AndroidDataMerger merger = AndroidDataMerger.createWithDefaults();
 
-    merger.merge(transitiveDependency, directDependency, primary, false);
+    merger.merge(transitiveDependency, directDependency, primary, false, false);
     assertThat(loggingHandler.warnings)
         .containsExactly(
             MergeConflict.of(
@@ -1073,7 +1113,7 @@ public class AndroidDataMergerTest {
 
     AndroidDataMerger merger = AndroidDataMerger.createWithDefaults();
     UnwrittenMergedAndroidData data =
-        merger.merge(transitiveDependency, directDependency, primary, true);
+        merger.merge(transitiveDependency, directDependency, primary, true, true);
     UnwrittenMergedAndroidData expected =
         UnwrittenMergedAndroidData.of(
             primary.getManifest(),
@@ -1109,7 +1149,7 @@ public class AndroidDataMergerTest {
 
     AndroidDataMerger merger = AndroidDataMerger.createWithDefaults();
 
-    merger.merge(transitiveDependency, directDependency, primary, false);
+    merger.merge(transitiveDependency, directDependency, primary, false, false);
     assertThat(loggingHandler.warnings)
         .containsExactly(
             MergeConflict.of(
@@ -1140,7 +1180,7 @@ public class AndroidDataMergerTest {
 
     AndroidDataMerger merger = AndroidDataMerger.createWithDefaults();
     UnwrittenMergedAndroidData data =
-        merger.merge(transitiveDependency, directDependency, primary, true);
+        merger.merge(transitiveDependency, directDependency, primary, true, true);
     UnwrittenMergedAndroidData expected =
         UnwrittenMergedAndroidData.of(
             primary.getManifest(),
@@ -1174,7 +1214,7 @@ public class AndroidDataMergerTest {
 
     AndroidDataMerger merger = AndroidDataMerger.createWithDefaults();
 
-    merger.merge(transitiveDependency, directDependency, primary, false);
+    merger.merge(transitiveDependency, directDependency, primary, false, false);
     assertThat(loggingHandler.warnings)
         .containsExactly(
             MergeConflict.of(
@@ -1209,7 +1249,7 @@ public class AndroidDataMergerTest {
 
     AndroidDataMerger merger = AndroidDataMerger.createWithDefaults();
 
-    merger.merge(transitiveDependency, directDependency, primary, false);
+    merger.merge(transitiveDependency, directDependency, primary, false, false);
     assertThat(loggingHandler.warnings)
         .containsExactly(
             MergeConflict.of(
@@ -1248,7 +1288,7 @@ public class AndroidDataMergerTest {
 
     UnwrittenMergedAndroidData data =
         AndroidDataMerger.createWithDefaults()
-            .merge(transitiveDependency, directDependency, primary, true);
+            .merge(transitiveDependency, directDependency, primary, true, true);
     
     UnwrittenMergedAndroidData expected =
         UnwrittenMergedAndroidData.of(
diff --git a/src/test/java/com/google/devtools/build/lib/rules/android/AndroidBinaryTest.java b/src/test/java/com/google/devtools/build/lib/rules/android/AndroidBinaryTest.java
index 9be5e5ca7f..704d6a4ee9 100644
--- a/src/test/java/com/google/devtools/build/lib/rules/android/AndroidBinaryTest.java
+++ b/src/test/java/com/google/devtools/build/lib/rules/android/AndroidBinaryTest.java
@@ -1569,6 +1569,24 @@ public class AndroidBinaryTest extends AndroidBuildViewTestCase {
     }
   }
 
+  @Test
+  public void testThrowOnResourceConflictFlagGetsPropagated() throws Exception {
+    scratch.file(
+        "java/r/android/BUILD",
+        "android_binary(",
+        "  name = 'r',",
+        "  manifest = 'AndroidManifest.xml',",
+        "  resource_files = ['res/values/foo.xml'],",
+        ")");
+    useConfiguration("--experimental_android_throw_on_resource_conflict");
+    ConfiguredTarget binary = getConfiguredTarget("//java/r/android:r");
+
+    List<String> resourceProcessingArgs =
+        resourceGeneratingAction(getResourceContainer(binary)).getArguments();
+
+    assertThat(resourceProcessingArgs).contains("--throwOnResourceConflict");
+  }
+
   /**
    * Gets the paths of matching artifacts contained within a resource container
    *
diff --git a/src/tools/android/java/com/google/devtools/build/android/AarGeneratorAction.java b/src/tools/android/java/com/google/devtools/build/android/AarGeneratorAction.java
index 7a6947d698..16091348c1 100644
--- a/src/tools/android/java/com/google/devtools/build/android/AarGeneratorAction.java
+++ b/src/tools/android/java/com/google/devtools/build/android/AarGeneratorAction.java
@@ -19,6 +19,7 @@ import com.google.common.base.Joiner;
 import com.google.common.base.Stopwatch;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Ordering;
+import com.google.devtools.build.android.AndroidDataMerger.MergeConflictException;
 import com.google.devtools.build.android.AndroidResourceMerger.MergingException;
 import com.google.devtools.build.android.Converters.ExistingPathConverter;
 import com.google.devtools.build.android.Converters.PathConverter;
@@ -124,6 +125,14 @@ public class AarGeneratorAction {
       help = "Path to write the archive."
     )
     public Path aarOutput;
+
+    @Option(name = "throwOnResourceConflict",
+        defaultValue = "false",
+        category = "config",
+        documentationCategory = OptionDocumentationCategory.UNCATEGORIZED,
+        effectTags = {OptionEffectTag.UNKNOWN},
+        help = "If passed, resource merge conflicts will be treated as errors instead of warnings")
+    public boolean throwOnResourceConflict;
   }
 
   public static void main(String[] args) {
@@ -153,12 +162,17 @@ public class AarGeneratorAction {
               null,
               VariantType.LIBRARY,
               null,
-              /* filteredResources= */ ImmutableList.<String>of());
+              /* filteredResources= */ ImmutableList.<String>of(),
+              options.throwOnResourceConflict
+          );
       logger.fine(String.format("Merging finished at %dms", timer.elapsed(TimeUnit.MILLISECONDS)));
 
       writeAar(options.aarOutput, mergedData, options.manifest, options.rtxt, options.classes);
       logger.fine(
           String.format("Packaging finished at %dms", timer.elapsed(TimeUnit.MILLISECONDS)));
+    } catch (MergeConflictException e) {
+      logger.log(Level.SEVERE, e.getMessage());
+      System.exit(1);
     } catch (IOException | MergingException e) {
       logger.log(Level.SEVERE, "Error during merging resources", e);
       System.exit(1);
diff --git a/src/tools/android/java/com/google/devtools/build/android/AndroidDataMerger.java b/src/tools/android/java/com/google/devtools/build/android/AndroidDataMerger.java
index 44967168b9..f5b0b0040e 100644
--- a/src/tools/android/java/com/google/devtools/build/android/AndroidDataMerger.java
+++ b/src/tools/android/java/com/google/devtools/build/android/AndroidDataMerger.java
@@ -36,6 +36,17 @@ import java.util.logging.Logger;
 /** Handles the Merging of ParsedAndroidData. */
 class AndroidDataMerger {
 
+  public static class MergeConflictException extends RuntimeException {
+
+    private MergeConflictException(String message) {
+      super(message);
+    }
+
+    static MergeConflictException withMessage(String message) {
+      return new MergeConflictException(message);
+    }
+  }
+
   private static final Logger logger = Logger.getLogger(AndroidDataMerger.class.getCanonicalName());
 
   /** Interface for comparing paths. */
@@ -70,7 +81,7 @@ class AndroidDataMerger {
               // getFileSize did not return correct size.
               logger.severe(
                   String.format(
-                      "Filesystem size of %s (%s) or %s (%s) is inconsistant with bytes read %s.",
+                      "Filesystem size of %s (%s) or %s (%s) is inconsistent with bytes read %s.",
                       one, one.getFileSize(), two, two.getFileSize(), bytesRead));
               return false;
             }
@@ -131,15 +142,15 @@ class AndroidDataMerger {
    * ParsedAndroidData}.
    *
    * @see AndroidDataMerger#merge(ParsedAndroidData, ParsedAndroidData, UnvalidatedAndroidData,
-   *     boolean) for details.
+   *     boolean, boolean) for details.
    */
   UnwrittenMergedAndroidData loadAndMerge(
       List<? extends SerializedAndroidData> transitive,
       List<? extends SerializedAndroidData> direct,
       ParsedAndroidData primary,
       Path primaryManifest,
-      boolean allowPrimaryOverrideAll)
-      throws MergingException {
+      boolean allowPrimaryOverrideAll,
+      boolean throwOnResourceConflict) {
     Stopwatch timer = Stopwatch.createStarted();
     try {
       logger.fine(
@@ -150,7 +161,8 @@ class AndroidDataMerger {
           ParsedAndroidData.loadedFrom(direct, executorService, deserializer),
           primary,
           primaryManifest,
-          allowPrimaryOverrideAll);
+          allowPrimaryOverrideAll,
+          throwOnResourceConflict);
     } finally {
       logger.fine(String.format("Resources merged in %sms", timer.elapsed(TimeUnit.MILLISECONDS)));
     }
@@ -218,20 +230,26 @@ class AndroidDataMerger {
    *     the ultimate source of truth, provided it doesn't conflict with itself.
    * @return An UnwrittenMergedAndroidData, containing DataResource objects that can be written to
    *     disk for aapt processing or serialized for future merge passes.
-   * @throws MergingException if there are merge conflicts or issues with parsing resources from
+   * @throws MergingException if there are issues with parsing resources from
    *     primaryData.
+   * @throws MergeConflictException if there are merge conflicts
    */
   UnwrittenMergedAndroidData merge(
       ParsedAndroidData transitive,
       ParsedAndroidData direct,
       UnvalidatedAndroidData primaryData,
-      boolean allowPrimaryOverrideAll)
-      throws MergingException {
+      boolean allowPrimaryOverrideAll,
+      boolean throwOnResourceConflict) {
     try {
       // Extract the primary resources.
       ParsedAndroidData parsedPrimary = ParsedAndroidData.from(primaryData);
       return doMerge(
-          transitive, direct, parsedPrimary, primaryData.getManifest(), allowPrimaryOverrideAll);
+          transitive,
+          direct,
+          parsedPrimary,
+          primaryData.getManifest(),
+          allowPrimaryOverrideAll,
+          throwOnResourceConflict);
     } catch (IOException e) {
       throw MergingException.wrapException(e);
     }
@@ -242,15 +260,14 @@ class AndroidDataMerger {
       ParsedAndroidData direct,
       ParsedAndroidData parsedPrimary,
       Path primaryManifest,
-      boolean allowPrimaryOverrideAll)
-      throws MergingException {
+      boolean allowPrimaryOverrideAll,
+      boolean throwOnResourceConflict) {
     try {
       // Create the builders for the final parsed data.
       final ParsedAndroidData.Builder primaryBuilder = ParsedAndroidData.Builder.newBuilder();
       final ParsedAndroidData.Builder transitiveBuilder = ParsedAndroidData.Builder.newBuilder();
       final KeyValueConsumers transitiveConsumers = transitiveBuilder.consumers();
       final KeyValueConsumers primaryConsumers = primaryBuilder.consumers();
-
       final Set<MergeConflict> conflicts = new HashSet<>();
 
       // Find all internal conflicts.
@@ -286,7 +303,7 @@ class AndroidDataMerger {
         if (allowPrimaryOverrideAll && parsedPrimary.containsOverwritable(entry.getKey())) {
           continue;
         }
-        // If a transitive value is in the direct map report a conflict, as it is commonly
+        // If a transitive value is in the direct map, report a conflict, as it is commonly
         // unintentional.
         if (direct.containsOverwritable(entry.getKey())) {
           conflicts.add(direct.foundResourceConflict(entry.getKey(), entry.getValue()));
@@ -367,8 +384,11 @@ class AndroidDataMerger {
           }
         }
         if (!messages.isEmpty()) {
-          // TODO(corysmith): Turn these into errors.
-          logger.warning(Joiner.on("").join(messages));
+          String conflictMessage = Joiner.on("").join(messages);
+          if (throwOnResourceConflict) {
+            throw MergeConflictException.withMessage(conflictMessage);
+          }
+          logger.warning(conflictMessage);
         }
       }
       return UnwrittenMergedAndroidData.of(
diff --git a/src/tools/android/java/com/google/devtools/build/android/AndroidResourceMerger.java b/src/tools/android/java/com/google/devtools/build/android/AndroidResourceMerger.java
index 8fc6075382..eb7fd70711 100644
--- a/src/tools/android/java/com/google/devtools/build/android/AndroidResourceMerger.java
+++ b/src/tools/android/java/com/google/devtools/build/android/AndroidResourceMerger.java
@@ -64,8 +64,8 @@ public class AndroidResourceMerger {
       final VariantType type,
       @Nullable final Path symbolsOut,
       @Nullable AndroidResourceClassWriter rclassWriter,
-      AndroidDataDeserializer deserializer)
-      throws MergingException {
+      AndroidDataDeserializer deserializer,
+      boolean throwOnResourceConflict) {
     Stopwatch timer = Stopwatch.createStarted();
     final ListeningExecutorService executorService =
         MoreExecutors.listeningDecorator(Executors.newFixedThreadPool(15));
@@ -78,7 +78,8 @@ public class AndroidResourceMerger {
               primary,
               primaryManifest,
               type != VariantType.LIBRARY,
-              deserializer);
+              deserializer,
+              throwOnResourceConflict);
       timer.reset().start();
       if (symbolsOut != null) {
         AndroidDataSerializer serializer = AndroidDataSerializer.create();
@@ -114,14 +115,19 @@ public class AndroidResourceMerger {
       ParsedAndroidData primary,
       Path primaryManifest,
       boolean allowPrimaryOverrideAll,
-      AndroidDataDeserializer deserializer)
-      throws MergingException {
+      AndroidDataDeserializer deserializer,
+      boolean throwOnResourceConflict) {
     Stopwatch timer = Stopwatch.createStarted();
     try {
       AndroidDataMerger merger =
           AndroidDataMerger.createWithPathDeduplictor(executorService, deserializer);
       return merger.loadAndMerge(
-          transitive, direct, primary, primaryManifest, allowPrimaryOverrideAll);
+          transitive,
+          direct,
+          primary,
+          primaryManifest,
+          allowPrimaryOverrideAll,
+          throwOnResourceConflict);
     } finally {
       logger.fine(String.format("merge finished in %sms", timer.elapsed(TimeUnit.MILLISECONDS)));
     }
@@ -140,8 +146,8 @@ public class AndroidResourceMerger {
       @Nullable final PngCruncher cruncher,
       final VariantType type,
       @Nullable final Path symbolsOut,
-      final List<String> filteredResources)
-      throws MergingException {
+      final List<String> filteredResources,
+      boolean throwOnResourceConflict) {
     try {
       final ParsedAndroidData parsedPrimary = ParsedAndroidData.from(primary);
       return mergeData(
@@ -155,7 +161,8 @@ public class AndroidResourceMerger {
           type,
           symbolsOut,
           null /* rclassWriter */,
-          AndroidDataDeserializer.withFilteredResources(filteredResources));
+          AndroidDataDeserializer.withFilteredResources(filteredResources),
+          throwOnResourceConflict);
     } catch (IOException e) {
       throw MergingException.wrapException(e);
     }
@@ -175,8 +182,8 @@ public class AndroidResourceMerger {
       @Nullable final PngCruncher cruncher,
       final VariantType type,
       @Nullable final Path symbolsOut,
-      @Nullable final AndroidResourceClassWriter rclassWriter)
-      throws MergingException {
+      @Nullable final AndroidResourceClassWriter rclassWriter,
+      boolean throwOnResourceConflict) {
     final ParsedAndroidData.Builder primaryBuilder = ParsedAndroidData.Builder.newBuilder();
     final AndroidDataDeserializer deserializer = AndroidDataDeserializer.create();
     primary.deserialize(deserializer, primaryBuilder.consumers());
@@ -192,7 +199,8 @@ public class AndroidResourceMerger {
         type,
         symbolsOut,
         rclassWriter,
-        deserializer);
+        deserializer,
+        throwOnResourceConflict);
   }
 }
 
diff --git a/src/tools/android/java/com/google/devtools/build/android/AndroidResourceMergingAction.java b/src/tools/android/java/com/google/devtools/build/android/AndroidResourceMergingAction.java
index 9459ae6d99..4506fae73e 100644
--- a/src/tools/android/java/com/google/devtools/build/android/AndroidResourceMergingAction.java
+++ b/src/tools/android/java/com/google/devtools/build/android/AndroidResourceMergingAction.java
@@ -21,6 +21,7 @@ import com.google.common.base.Preconditions;
 import com.google.common.base.Stopwatch;
 import com.google.common.base.Strings;
 import com.google.common.io.Files;
+import com.google.devtools.build.android.AndroidDataMerger.MergeConflictException;
 import com.google.devtools.build.android.AndroidResourceMerger.MergingException;
 import com.google.devtools.build.android.AndroidResourceProcessor.AaptConfigOptions;
 import com.google.devtools.build.android.Converters.ExistingPathConverter;
@@ -180,6 +181,14 @@ public class AndroidResourceMergingAction {
       help = "Path to where data binding's layout info output should be written."
     )
     public Path dataBindingInfoOut;
+
+    @Option(name = "throwOnResourceConflict",
+        defaultValue = "false",
+        category = "config",
+        documentationCategory = OptionDocumentationCategory.UNCATEGORIZED,
+        effectTags = {OptionEffectTag.UNKNOWN},
+        help = "If passed, resource merge conflicts will be treated as errors instead of warnings")
+    public boolean throwOnResourceConflict;
   }
 
   public static void main(String[] args) throws Exception {
@@ -223,7 +232,8 @@ public class AndroidResourceMergingAction {
               new StubPngCruncher(),
               packageType,
               options.symbolsBinOut,
-              resourceClassWriter);
+              resourceClassWriter,
+              options.throwOnResourceConflict);
 
       logger.fine(String.format("Merging finished at %sms", timer.elapsed(TimeUnit.MILLISECONDS)));
 
@@ -268,6 +278,9 @@ public class AndroidResourceMergingAction {
             String.format(
                 "Create resources.zip finished at %sms", timer.elapsed(TimeUnit.MILLISECONDS)));
       }
+    } catch (MergeConflictException e) {
+      logger.log(Level.SEVERE, e.getMessage());
+      System.exit(1);
     } catch (MergingException e) {
       logger.log(Level.SEVERE, "Error during merging resources", e);
       throw e;
diff --git a/src/tools/android/java/com/google/devtools/build/android/AndroidResourceProcessingAction.java b/src/tools/android/java/com/google/devtools/build/android/AndroidResourceProcessingAction.java
index 13eb0f5c90..0dfd21e5f5 100644
--- a/src/tools/android/java/com/google/devtools/build/android/AndroidResourceProcessingAction.java
+++ b/src/tools/android/java/com/google/devtools/build/android/AndroidResourceProcessingAction.java
@@ -22,6 +22,7 @@ import com.android.ide.common.process.LoggedProcessOutputHandler;
 import com.android.utils.StdLogger;
 import com.google.common.base.Stopwatch;
 import com.google.common.collect.ImmutableSet;
+import com.google.devtools.build.android.AndroidDataMerger.MergeConflictException;
 import com.google.devtools.build.android.AndroidResourceMerger.MergingException;
 import com.google.devtools.build.android.AndroidResourceProcessor.AaptConfigOptions;
 import com.google.devtools.build.android.AndroidResourceProcessor.FlagAaptOptions;
@@ -295,6 +296,14 @@ public class AndroidResourceProcessingAction {
       help = "A list of resources that were filtered out in analysis."
     )
     public List<String> prefilteredResources;
+
+    @Option(name = "throwOnResourceConflict",
+        defaultValue = "false",
+        category = "config",
+        documentationCategory = OptionDocumentationCategory.UNCATEGORIZED,
+        effectTags = {OptionEffectTag.UNKNOWN},
+        help = "If passed, resource merge conflicts will be treated as errors instead of warnings")
+    public boolean throwOnResourceConflict;
   }
 
   private static AaptConfigOptions aaptConfigOptions;
@@ -346,7 +355,8 @@ public class AndroidResourceProcessingAction {
               selectPngCruncher(),
               options.packageType,
               options.symbolsOut,
-              options.prefilteredResources);
+              options.prefilteredResources,
+              options.throwOnResourceConflict);
 
       logger.fine(String.format("Merging finished at %sms", timer.elapsed(TimeUnit.MILLISECONDS)));
 
@@ -429,6 +439,9 @@ public class AndroidResourceProcessingAction {
       }
       logger.fine(
           String.format("Packaging finished at %sms", timer.elapsed(TimeUnit.MILLISECONDS)));
+    } catch (MergeConflictException e) {
+      logger.severe(e.getMessage());
+      System.exit(1);
     } catch (MergingException e) {
       logger.log(java.util.logging.Level.SEVERE, "Error during merging resources", e);
       throw e;