Add minSdkVersion optimization to Blaze.

This optimization reduces the size of Android apps that use Proguard by ~0.2 - 0.3% depending on the minSdkVersion.

RELNOTES: None.
PiperOrigin-RevId: 160673030

3 files changed, 21 insertions, 0 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/bazel/rules/android/BazelAndroidSemantics.java b/src/main/java/com/google/devtools/build/lib/bazel/rules/android/BazelAndroidSemantics.java
index 31eedc4da4..e7fee2789b 100644
--- a/src/main/java/com/google/devtools/build/lib/bazel/rules/android/BazelAndroidSemantics.java
+++ b/src/main/java/com/google/devtools/build/lib/bazel/rules/android/BazelAndroidSemantics.java
@@ -91,6 +91,12 @@ public class BazelAndroidSemantics implements AndroidSemantics {
   }
 
   @Override
+  public ImmutableList<Artifact> getProguardSpecsForManifest(
+      RuleContext ruleContext, Artifact manifest) {
+    return ImmutableList.of();
+  }
+
+  @Override
   public void addCoverageSupport(RuleContext ruleContext, AndroidCommon common,
       JavaSemantics javaSemantics, boolean forAndroidTest, Builder attributes,
       JavaCompilationArtifacts.Builder artifactsBuilder) {
diff --git a/src/main/java/com/google/devtools/build/lib/rules/android/AndroidBinary.java b/src/main/java/com/google/devtools/build/lib/rules/android/AndroidBinary.java
index 438748c5ec..0be53c07f2 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/android/AndroidBinary.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/android/AndroidBinary.java
@@ -422,6 +422,18 @@ public abstract class AndroidBinary implements RuleConfiguredTargetFactory {
     ImmutableList<Artifact> proguardSpecs = ProguardHelper.collectTransitiveProguardSpecs(
         ruleContext, ImmutableList.of(resourceApk.getResourceProguardConfig()));
 
+    // NB: Order here is important. We're including generated Proguard specs before the user's specs
+    // so that they can override values.
+    if (!proguardSpecs.isEmpty()) {
+      proguardSpecs =
+          ImmutableList.<Artifact>builder()
+              .addAll(
+                  androidSemantics.getProguardSpecsForManifest(
+                      ruleContext, applicationManifest.getManifest()))
+              .addAll(proguardSpecs)
+              .build();
+    }
+
     boolean rexEnabled =
         ruleContext.getFragment(AndroidConfiguration.class).useRexToCompressDexFiles()
         || (ruleContext.attributes().get("rewrite_dexes_with_rex", Type.BOOLEAN));
diff --git a/src/main/java/com/google/devtools/build/lib/rules/android/AndroidSemantics.java b/src/main/java/com/google/devtools/build/lib/rules/android/AndroidSemantics.java
index b791b69f01..cd2e1eeecc 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/android/AndroidSemantics.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/android/AndroidSemantics.java
@@ -97,6 +97,9 @@ public interface AndroidSemantics {
    */
   Artifact getApkDebugSigningKey(RuleContext ruleContext);
 
+  /** Given an Android {@code manifest}, returns a list of relevant Proguard specs. */
+  ImmutableList<Artifact> getProguardSpecsForManifest(RuleContext ruleContext, Artifact manifest);
+
   /**
    * Add coverage instrumentation to the Java compilation of an Android binary.
    * @throws InterruptedException