xds: Handle empty target URI authorities the same as null.

MODULE.bazel

@@ -41,6 +41,7 @@ IO_GRPC_GRPC_JAVA_ARTIFACTS = [
     "io.opencensus:opencensus-contrib-grpc-metrics:0.31.0",
     "io.perfmark:perfmark-api:0.27.0",
     "junit:junit:4.13.2",
+    "org.mockito:mockito-core:4.4.0",
     "org.checkerframework:checker-qual:3.49.5",
     "org.codehaus.mojo:animal-sniffer-annotations:1.26",
 ]

api/BUILD.bazel

@@ -15,3 +15,21 @@ java_library(
         artifact("com.google.guava:guava"),
     ],
 )
+
+java_library(
+    name = "test_fixtures",
+    testonly = 1,
+    srcs = glob([
+        "src/testFixtures/java/io/grpc/**/*.java",
+    ]),
+    visibility = ["//xds:__pkg__"],
+    deps = [
+        "//core",
+        artifact("com.google.code.findbugs:jsr305"),
+        artifact("com.google.errorprone:error_prone_annotations"),
+        artifact("com.google.guava:guava"),
+        artifact("com.google.truth:truth"),
+        artifact("junit:junit"),
+        artifact("org.mockito:mockito-core"),
+    ],
+)

repositories.bzl

@@ -45,6 +45,7 @@ IO_GRPC_GRPC_JAVA_ARTIFACTS = [
     "io.opencensus:opencensus-contrib-grpc-metrics:0.31.0",
     "io.perfmark:perfmark-api:0.27.0",
     "junit:junit:4.13.2",
+    "org.mockito:mockito-core:4.4.0",
     "org.checkerframework:checker-qual:3.49.5",
     "org.codehaus.mojo:animal-sniffer-annotations:1.26",
 ]

xds/BUILD.bazel

@@ -343,6 +343,7 @@ java_library(
         ":xds",
         ":xds_java_proto",
         "//api",
+        "//api:test_fixtures",
         "//core:internal",
         "//stub",
         "//testing-proto:simpleservice_java_grpc",

xds/src/main/java/io/grpc/xds/XdsNameResolver.java

@@ -138,6 +138,13 @@ final class XdsNameResolver extends NameResolver {
   private CallCounterProvider callCounterProvider;
   private ResolveState resolveState;
 
+  /**
+   * Constructs a new instance.
+   *
+   * @param target the target URI to resolve
+   * @param targetAuthority the authority component of `target`, possibly the empty string, or null
+   *     if 'target' has no such component
+   */
   XdsNameResolver(
       String target, @Nullable String targetAuthority, String name,
       @Nullable String overrideAuthority, ServiceConfigParser serviceConfigParser,
@@ -208,7 +215,9 @@ public void start(Listener2 listener) {
     }
     BootstrapInfo bootstrapInfo = xdsClient.getBootstrapInfo();
     String listenerNameTemplate;
-    if (targetAuthority == null) {
+    if (targetAuthority == null || targetAuthority.isEmpty()) {
+      // Both https://github.com/grpc/proposal/blob/master/A27-xds-global-load-balancing.md and
+      // A47-xds-federation.md seem to treat an empty authority the same as an undefined one.
       listenerNameTemplate = bootstrapInfo.clientDefaultListenerResourceNameTemplate();
     } else {
       AuthorityInfo authorityInfo = bootstrapInfo.authorities().get(targetAuthority);

xds/src/main/java/io/grpc/xds/XdsNameResolverProvider.java

@@ -87,7 +87,11 @@ public XdsNameResolver newNameResolver(URI targetUri, Args args) {
           targetPath,
           targetUri);
       String name = targetPath.substring(1);
-      return newNameResolver(targetUri.toString(), targetUri.getAuthority(), name, args);
+      // TODO(jdcormie): java.net.URI#getAuthority incorrectly returns null for both xds:///service
+      //  and xds:/service. This doesn't matter for now since XdsNameResolver treats them the same
+      //  anyway and all this code will go away once newNameResolver(io.grpc.Uri) launches.
+      String targetAuthority = targetUri.getAuthority();
+      return newNameResolver(targetUri.toString(), targetAuthority, name, args);
     }
     return null;
   }

xds/src/test/java/io/grpc/xds/FakeControlPlaneXdsIntegrationTest.java

@@ -50,8 +50,10 @@
 import io.grpc.ClientCall;
 import io.grpc.ClientInterceptor;
 import io.grpc.ClientStreamTracer;
+import io.grpc.FlagResetRule;
 import io.grpc.ForwardingClientCall.SimpleForwardingClientCall;
 import io.grpc.ForwardingClientCallListener;
+import io.grpc.InternalFeatureFlags;
 import io.grpc.LoadBalancerRegistry;
 import io.grpc.ManagedChannel;
 import io.grpc.Metadata;
@@ -60,10 +62,14 @@
 import io.grpc.testing.protobuf.SimpleResponse;
 import io.grpc.testing.protobuf.SimpleServiceGrpc;
 import java.net.InetSocketAddress;
+import java.util.Arrays;
+import org.junit.Before;
 import org.junit.Rule;
 import org.junit.Test;
 import org.junit.runner.RunWith;
-import org.junit.runners.JUnit4;
+import org.junit.runners.Parameterized;
+import org.junit.runners.Parameterized.Parameter;
+import org.junit.runners.Parameterized.Parameters;
 
 /**
  * Xds integration tests using a local control plane, implemented in {@link
@@ -85,13 +91,28 @@
  * 3) Construct EDS config w/ test server address from 2). Set CDS and EDS Config at the Control
  * Plane. Then start the test xDS client (requires EDS to do xDS name resolution).
  */
-@RunWith(JUnit4.class)
+@RunWith(Parameterized.class)
 public class FakeControlPlaneXdsIntegrationTest {
 
   @Rule(order = 0)
   public ControlPlaneRule controlPlane = new ControlPlaneRule();
   @Rule(order = 1)
   public DataPlaneRule dataPlane = new DataPlaneRule(controlPlane);
+  @Rule(order = 2)
+  public final FlagResetRule flagResetRule = new FlagResetRule();
+
+  @Parameters(name = "enableRfc3986UrisParam={0}")
+  public static Iterable<Object[]> data() {
+    return Arrays.asList(new Object[][] {{true}, {false}});
+  }
+
+  @Parameter public boolean enableRfc3986UrisParam;
+
+  @Before
+  public void setupRfc3986UrisFeatureFlag() throws Exception {
+    flagResetRule.setFlagForTest(
+        InternalFeatureFlags::setRfc3986UrisEnabled, enableRfc3986UrisParam);
+  }
 
   @Test
   public void pingPong() throws Exception {

xds/src/test/java/io/grpc/xds/XdsNameResolverTest.java

@@ -297,6 +297,40 @@ public void resolving_noTargetAuthority_templateWithoutXdstp() {
     verify(mockListener, never()).onError(any(Status.class));
   }
 
+  @Test
+  public void resolving_emptyTargetAuthority_templateWithXdstp() {
+    bootstrapInfo =
+        BootstrapInfo.builder()
+            .servers(
+                ImmutableList.of(
+                    ServerInfo.create("td.googleapis.com", InsecureChannelCredentials.create())))
+            .node(Node.newBuilder().build())
+            .clientDefaultListenerResourceNameTemplate(
+                "xdstp://xds.authority.com/envoy.config.listener.v3.Listener/%s?id=1")
+            .build();
+    String serviceAuthority = "[::FFFF:129.144.52.38]:80";
+    expectedLdsResourceName =
+        "xdstp://xds.authority.com/envoy.config.listener.v3.Listener/"
+            + "%5B::FFFF:129.144.52.38%5D:80?id=1";
+    resolver =
+        new XdsNameResolver(
+            "xds:///foo.googleapis.com",
+            "",
+            serviceAuthority,
+            null,
+            serviceConfigParser,
+            syncContext,
+            scheduler,
+            xdsClientPoolFactory,
+            mockRandom,
+            FilterRegistry.getDefaultRegistry(),
+            rawBootstrap,
+            metricRecorder,
+            nameResolverArgs);
+    resolver.start(mockListener);
+    verify(mockListener, never()).onError(any(Status.class));
+  }
+
   @Test
   public void resolving_noTargetAuthority_templateWithXdstp() {
     bootstrapInfo = BootstrapInfo.builder()