Introduce a NameResolver for Android's intent: URIs (#12248)

Let grpc-binder clients find on-device services by [implicit Intent](https://developer.android.com/guide/components/intents-filters#Types) target URI, lifting the need to hard code a server's package name.

Author: jdcormie

api/src/main/java/io/grpc/NameResolverRegistry.java

@@ -166,6 +166,11 @@ static List<Class<?>> getHardCodedClasses() {
     } catch (ClassNotFoundException e) {
       logger.log(Level.FINE, "Unable to find DNS NameResolver", e);
     }
+    try {
+      list.add(Class.forName("io.grpc.binder.internal.IntentNameResolverProvider"));
+    } catch (ClassNotFoundException e) {
+      logger.log(Level.FINE, "Unable to find IntentNameResolverProvider", e);
+    }
     return Collections.unmodifiableList(list);
   }
 

binder/src/androidTest/AndroidManifest.xml

@@ -11,11 +11,13 @@
     <service android:name="io.grpc.binder.HostServices$HostService1" android:exported="false">
       <intent-filter>
         <action android:name="action1"/>
+        <data android:scheme="scheme" android:host="authority" android:path="/path"/>
       </intent-filter>
     </service>
     <service android:name="io.grpc.binder.HostServices$HostService2" android:exported="false">
       <intent-filter>
         <action android:name="action2"/>
+        <data android:scheme="scheme" android:host="authority" android:path="/path"/>
       </intent-filter>
     </service>
   </application>

binder/src/androidTest/java/io/grpc/binder/BinderChannelSmokeTest.java

@@ -23,6 +23,7 @@
 
 import android.content.Context;
 import android.content.Intent;
+import android.net.Uri;
 import android.os.Parcel;
 import android.os.Parcelable;
 import androidx.test.core.app.ApplicationProvider;
@@ -39,7 +40,6 @@
 import io.grpc.ManagedChannel;
 import io.grpc.Metadata;
 import io.grpc.MethodDescriptor;
-import io.grpc.NameResolverRegistry;
 import io.grpc.ServerCall;
 import io.grpc.ServerCall.Listener;
 import io.grpc.ServerCallHandler;
@@ -49,7 +49,6 @@
 import io.grpc.Status.Code;
 import io.grpc.StatusRuntimeException;
 import io.grpc.internal.GrpcUtil;
-import io.grpc.internal.testing.FakeNameResolverProvider;
 import io.grpc.stub.ClientCalls;
 import io.grpc.stub.MetadataUtils;
 import io.grpc.stub.ServerCalls;
@@ -77,7 +76,6 @@ public final class BinderChannelSmokeTest {
 
   private static final int SLIGHTLY_MORE_THAN_ONE_BLOCK = 16 * 1024 + 100;
   private static final String MSG = "Some text which will be repeated many many times";
-  private static final String SERVER_TARGET_URI = "fake://server";
   private static final Metadata.Key<PoisonParcelable> POISON_KEY =
       ParcelableUtils.metadataKey("poison-bin", PoisonParcelable.CREATOR);
 
@@ -99,7 +97,6 @@ public final class BinderChannelSmokeTest {
           .setType(MethodDescriptor.MethodType.BIDI_STREAMING)
           .build();
 
-  FakeNameResolverProvider fakeNameResolverProvider;
   ManagedChannel channel;
   AtomicReference<Metadata> headersCapture = new AtomicReference<>();
   AtomicReference<PeerUid> clientUidCapture = new AtomicReference<>();
@@ -138,8 +135,6 @@ public void setUp() throws Exception {
             PeerUids.newPeerIdentifyingServerInterceptor());
 
     AndroidComponentAddress serverAddress = HostServices.allocateService(appContext);
-    fakeNameResolverProvider = new FakeNameResolverProvider(SERVER_TARGET_URI, serverAddress);
-    NameResolverRegistry.getDefaultRegistry().register(fakeNameResolverProvider);
     HostServices.configureService(
         serverAddress,
         HostServices.serviceParamsBuilder()
@@ -166,7 +161,6 @@ public void setUp() throws Exception {
   @After
   public void tearDown() throws Exception {
     channel.shutdownNow();
-    NameResolverRegistry.getDefaultRegistry().deregister(fakeNameResolverProvider);
     HostServices.awaitServiceShutdown();
   }
 
@@ -235,7 +229,11 @@ public void testStreamingCallOptionHeaders() throws Exception {
 
   @Test
   public void testConnectViaTargetUri() throws Exception {
-    channel = BinderChannelBuilder.forTarget(SERVER_TARGET_URI, appContext).build();
+    // Compare with the <intent-filter> mapping in AndroidManifest.xml.
+    channel =
+        BinderChannelBuilder.forTarget(
+                "intent://authority/path#Intent;action=action1;scheme=scheme;end;", appContext)
+            .build();
     assertThat(doCall("Hello").get()).isEqualTo("Hello");
   }
 
@@ -245,7 +243,10 @@ public void testConnectViaIntentFilter() throws Exception {
     channel =
         BinderChannelBuilder.forAddress(
                 AndroidComponentAddress.forBindIntent(
-                    new Intent().setAction("action1").setPackage(appContext.getPackageName())),
+                    new Intent()
+                        .setAction("action1")
+                        .setData(Uri.parse("scheme://authority/path"))
+                        .setPackage(appContext.getPackageName())),
                 appContext)
             .build();
     assertThat(doCall("Hello").get()).isEqualTo("Hello");

binder/src/main/java/io/grpc/binder/ApiConstants.java

@@ -34,6 +34,18 @@ private ApiConstants() {}
    */
   public static final String ACTION_BIND = "grpc.io.action.BIND";
 
+  /**
+   * Gives a {@link NameResolver} access to its Channel's "source" {@link android.content.Context},
+   * the entry point to almost every other Android API.
+   *
+   * <p>This argument is set automatically by {@link BinderChannelBuilder}. Any value passed to
+   * {@link io.grpc.ManagedChannelBuilder#setNameResolverArg} will be ignored.
+   *
+   * <p>See {@link BinderChannelBuilder#forTarget(String, android.content.Context)} for more.
+   */
+  public static final NameResolver.Args.Key<android.content.Context> SOURCE_ANDROID_CONTEXT =
+      NameResolver.Args.Key.create("source-android-context");
+
   /**
    * Specifies the Android user in which target URIs should be resolved.
    *

binder/src/main/java/io/grpc/binder/BinderChannelBuilder.java

@@ -321,6 +321,8 @@ public BinderChannelBuilder idleTimeout(long value, TimeUnit unit) {
   public ManagedChannel build() {
     transportFactoryBuilder.setOffloadExecutorPool(
         managedChannelImplBuilder.getOffloadExecutorPool());
+    setNameResolverArg(
+        ApiConstants.SOURCE_ANDROID_CONTEXT, transportFactoryBuilder.getSourceContext());
     return super.build();
   }
 }

binder/src/main/java/io/grpc/binder/internal/BinderClientTransportFactory.java

@@ -142,6 +142,10 @@ public Builder setSourceContext(Context sourceContext) {
       return this;
     }
 
+    public Context getSourceContext() {
+      return sourceContext;
+    }
+
     public Builder setOffloadExecutorPool(ObjectPool<? extends Executor> offloadExecutorPool) {
       this.offloadExecutorPool = checkNotNull(offloadExecutorPool, "offloadExecutorPool");
       return this;