Add fix for xdstp replacement for encoded authorities

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

@@ -105,6 +105,9 @@ final class XdsNameResolver extends NameResolver {
   @Nullable
   private final String targetAuthority;
   private final String serviceAuthority;
+  // Encoded version of the service authority as per 
+  // https://datatracker.ietf.org/doc/html/rfc3986#section-3.2.
+  private final String encodedServiceAuthority;
   private final String overrideAuthority;
   private final ServiceConfigParser serviceConfigParser;
   private final SynchronizationContext syncContext;
@@ -149,8 +152,9 @@ final class XdsNameResolver extends NameResolver {
     this.targetAuthority = targetAuthority;
 
     // The name might have multiple slashes so encode it before verifying.
-    String authority = GrpcUtil.AuthorityEscaper.encodeAuthority(checkNotNull(name, "name"));
-    serviceAuthority = GrpcUtil.checkAuthority(authority);
+    serviceAuthority = checkNotNull(name, "name");
+    this.encodedServiceAuthority = 
+      GrpcUtil.checkAuthority(GrpcUtil.AuthorityEscaper.encodeAuthority(serviceAuthority));
 
     this.overrideAuthority = overrideAuthority;
     this.serviceConfigParser = checkNotNull(serviceConfigParser, "serviceConfigParser");
@@ -169,7 +173,7 @@ final class XdsNameResolver extends NameResolver {
 
   @Override
   public String getServiceAuthority() {
-    return serviceAuthority;
+    return encodedServiceAuthority;
   }
 
   @Override

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

@@ -265,6 +265,31 @@ public void resolving_noTargetAuthority_templateWithXdstp() {
     verify(mockListener, never()).onError(any(Status.class));
   }
 
+  @Test
+  public void resolving_noTargetAuthority_xdstpWithMultipleSlashes() {
+    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 = "path/to/service";
+    expectedLdsResourceName =
+        "xdstp://xds.authority.com/envoy.config.listener.v3.Listener/"
+            + "path/to/service?id=1";
+    resolver = new XdsNameResolver(
+        null, serviceAuthority, null, serviceConfigParser, syncContext, scheduler,
+        xdsClientPoolFactory, mockRandom, FilterRegistry.getDefaultRegistry(), null);
+
+
+    // The Service Authority must be URL encoded, but unlike the LDS resource name.
+    assertThat(resolver.getServiceAuthority()).isEqualTo("path%2Fto%2Fservice");
+
+    resolver.start(mockListener);
+    verify(mockListener, never()).onError(any(Status.class));
+  }
+
   @Test
   public void resolving_targetAuthorityInAuthoritiesMap() {
     String targetAuthority = "xds.authority.com";