Helper class to allow in process servers to use peer uids in test

binder/build.gradle

@@ -56,6 +56,7 @@ dependencies {
     testImplementation project(':grpc-testing')
     testImplementation project(':grpc-inprocess')
     testImplementation testFixtures(project(':grpc-core'))
+    testImplementation project(':grpc-binder')
 
     androidTestAnnotationProcessor libraries.auto.value
     androidTestImplementation project(':grpc-testing')

binder/src/test/java/io/grpc/binder/PeerUidTestHelperTest.java

@@ -0,0 +1,120 @@
+package io.grpc.binder;
+
+import static com.google.common.truth.Truth.assertThat;
+import static java.nio.charset.StandardCharsets.UTF_8;
+
+import com.google.common.collect.ImmutableList;
+import io.grpc.CallOptions;
+import io.grpc.Channel;
+import io.grpc.ClientInterceptors;
+import io.grpc.ManagedChannel;
+import io.grpc.Metadata;
+import io.grpc.MethodDescriptor;
+import io.grpc.ServerCallHandler;
+import io.grpc.ServerInterceptor;
+import io.grpc.ServerInterceptors;
+import io.grpc.ServerServiceDefinition;
+import io.grpc.inprocess.InProcessChannelBuilder;
+import io.grpc.inprocess.InProcessServerBuilder;
+import io.grpc.stub.ClientCalls;
+import io.grpc.stub.MetadataUtils;
+import io.grpc.stub.ServerCalls;
+import io.grpc.testing.GrpcCleanupRule;
+import java.io.ByteArrayInputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.concurrent.atomic.AtomicReference;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+@RunWith(JUnit4.class)
+public final class PeerUidTestHelperTest {
+    @Rule public final GrpcCleanupRule grpcCleanup = new GrpcCleanupRule();
+
+    private static final int FAKE_UID = 12345;
+
+    private final AtomicReference<PeerUid> clientUidCapture = new AtomicReference<>();
+
+    @Test
+    public void keyPopulatedWithInterceptorAndHeader() throws Exception {
+        makeServiceCall(/* includeInterceptor= */ true, /* includeUidInHeader= */ true, FAKE_UID);
+        assertThat(clientUidCapture.get()).isEqualTo(new PeerUid(FAKE_UID));
+    }
+
+    @Test
+    public void keyNotPopulatedWithInterceptorAndNoHeader() throws Exception {
+        makeServiceCall(/* includeInterceptor= */ true, /* includeUidInHeader= */ false, /* uid= */ -1);
+        assertThat(clientUidCapture.get()).isNull();
+    }
+
+    @Test
+    public void keyNotPopulatedWithoutInterceptorAndWithHeader() throws Exception {
+        makeServiceCall(
+                /* includeInterceptor= */ false, /* includeUidInHeader= */ true, /* uid= */ FAKE_UID);
+        assertThat(clientUidCapture.get()).isNull();
+    }
+
+    private final MethodDescriptor<String, String> method =
+            MethodDescriptor.newBuilder(StringMarshaller.INSTANCE, StringMarshaller.INSTANCE)
+                    .setFullMethodName("test/method")
+                    .setType(MethodDescriptor.MethodType.UNARY)
+                    .build();
+
+    private void makeServiceCall(boolean includeInterceptor, boolean includeUidInHeader, int uid)
+            throws Exception {
+        ServerCallHandler<String, String> callHandler =
+                ServerCalls.asyncUnaryCall(
+                        (req, respObserver) -> {
+                            clientUidCapture.set(PeerUids.REMOTE_PEER.get());
+                            respObserver.onNext(req);
+                            respObserver.onCompleted();
+                        });
+        ImmutableList<ServerInterceptor> interceptors;
+        if (includeInterceptor) {
+            interceptors = ImmutableList.of(PeerUidTestHelper.newTestPeerIdentifyingServerInterceptor());
+        } else {
+            interceptors = ImmutableList.of();
+        }
+        ServerServiceDefinition serviceDef =
+                ServerInterceptors.intercept(
+                        ServerServiceDefinition.builder("test").addMethod(method, callHandler).build(),
+                        interceptors);
+
+        InProcessServerBuilder server =
+                InProcessServerBuilder.forName("test").directExecutor().addService(serviceDef);
+
+        grpcCleanup.register(server.build().start());
+
+        Channel channel = InProcessChannelBuilder.forName("test").directExecutor().build();
+        grpcCleanup.register((ManagedChannel) channel);
+
+        if (includeUidInHeader) {
+            Metadata header = new Metadata();
+            header.put(PeerUidTestHelper.UID_KEY, uid);
+            channel =
+                    ClientInterceptors.intercept(channel, MetadataUtils.newAttachHeadersInterceptor(header));
+        }
+
+        ClientCalls.blockingUnaryCall(channel, method, CallOptions.DEFAULT, "hello");
+    }
+
+    private static class StringMarshaller implements MethodDescriptor.Marshaller<String> {
+        public static final StringMarshaller INSTANCE = new StringMarshaller();
+
+        @Override
+        public InputStream stream(String value) {
+            return new ByteArrayInputStream(value.getBytes(UTF_8));
+        }
+
+        @Override
+        public String parse(InputStream stream) {
+            try {
+                return new String(stream.readAllBytes(), UTF_8);
+            } catch (IOException ex) {
+                throw new RuntimeException(ex);
+            }
+        }
+    }
+}

binder/src/testFixtures/java/io/grpc/binder/PeerUidTestHelper.java

@@ -0,0 +1,56 @@
+package io.grpc.binder;
+
+import io.grpc.Context;
+import io.grpc.Contexts;
+import io.grpc.Metadata;
+import io.grpc.ServerCall;
+import io.grpc.ServerCallHandler;
+import io.grpc.ServerInterceptor;
+
+/** Class which helps set up {@link PeerUids} to be used in tests. */
+public class PeerUidTestHelper {
+
+    /** The UID of the calling package is set with the value of this key. */
+    public static final Metadata.Key<Integer> UID_KEY =
+            Metadata.Key.of("binder-remote-uid-for-unit-testing", PeerUidTestMarshaller.INSTANCE);
+
+    /**
+     * Creates an interceptor that associates the {@link PeerUids#REMOTE_PEER} key in the request
+     * {@link Context} with a UID provided by the client in the {@link #UID_KEY} request header, if
+     * present.
+     *
+     * <p>The returned interceptor works with any gRPC transport but is meant for in-process unit
+     * testing of gRPC/binder services that depend on {@link PeerUids}.
+     */
+    public static ServerInterceptor newTestPeerIdentifyingServerInterceptor() {
+        return new ServerInterceptor() {
+            @Override
+            public <ReqT, RespT> ServerCall.Listener<ReqT> interceptCall(
+                    ServerCall<ReqT, RespT> call, Metadata headers, ServerCallHandler<ReqT, RespT> next) {
+                Context context = Context.current();
+                if (headers.containsKey(UID_KEY)) {
+                    context = context.withValue(PeerUids.REMOTE_PEER, new PeerUid(headers.get(UID_KEY)));
+                }
+
+                return Contexts.interceptCall(context, call, headers, next);
+            }
+        };
+    }
+
+    private PeerUidTestHelper() {}
+
+    private static class PeerUidTestMarshaller implements Metadata.AsciiMarshaller<Integer> {
+        public static final PeerUidTestMarshaller INSTANCE = new PeerUidTestMarshaller();
+
+        @Override
+        public String toAsciiString(Integer value) {
+            return value.toString();
+        }
+
+        @Override
+        public Integer parseAsciiString(String serialized) {
+            return Integer.parseInt(serialized);
+        }
+    }
+    ;
+}