fix: Endpoint resolution uses user set endpoint from ClientSettings (#2429)

* fix: Endpoint resolution uses the user set endpoint

* chore: Rename to userSetEndpoint()

* chore: Empty commit

* chore: Fix showcase tests

Author: lqiu96

gax-java/gax/src/main/java/com/google/api/gax/rpc/ClientContext.java

@@ -165,7 +165,7 @@ public static ClientContext create(StubSettings settings) throws IOException {
         EndpointContext.newBuilder()
             .setServiceName(settings.getServiceName())
             .setUniverseDomain(settings.getUniverseDomain())
-            .setClientSettingsEndpoint(settings.getEndpoint())
+            .setClientSettingsEndpoint(settings.getUserSetEndpoint())
             .setTransportChannelProviderEndpoint(
                 settings.getTransportChannelProvider().getEndpoint())
             .setMtlsEndpoint(settings.getMtlsEndpoint())

gax-java/gax/src/main/java/com/google/api/gax/rpc/StubSettings.java

@@ -157,6 +157,17 @@ public String getEndpoint() {
     return endpoint;
   }
 
+  /**
+   * This is an internal api meant to either return the user set endpoint or null. The difference
+   * between this method and {@link #getEndpoint()}} is that {@link #getEndpoint()} is reimplemented
+   * by the child class and will return the default service endpoint if the user did not set an
+   * endpoint (does not return null).
+   */
+  @InternalApi
+  String getUserSetEndpoint() {
+    return endpoint;
+  }
+
   public final String getMtlsEndpoint() {
     return mtlsEndpoint;
   }

showcase/gapic-showcase/src/test/java/com/google/showcase/v1beta1/it/ITEndpointContext.java

@@ -20,14 +20,23 @@ public class ITEndpointContext {
   public static final String SHOWCASE_DEFAULT_ENDPOINT = "localhost:7469";
 
   // Default (no configuration)
+  // This test is very similar to `endpointResolution_userConfiguration`. This test is kept
+  // as future enhancements could allow this test to not have to explicitly set the endpoint.
   @Test
   public void endpointResolution_default() throws InterruptedException, IOException {
     EchoClient echoClient = null;
     try {
-      // The default usage is EchoClient.create(), but for showcase tests run in CI, the
+      // This is not how a client is created by default:
+      // 1. The default usage is EchoClient.create(), but for showcase tests run in CI, the
       // client must be supplied with Credentials.
+      // 2. The default configuration does not set an endpoint. Showcase clients do not have
+      // a serviceName (and this cannot be configured by the user). Set the endpoint
+      // to simulate the endpointContext creating it with a proper serviceName.
       EchoSettings echoSettings =
-          EchoSettings.newBuilder().setCredentialsProvider(NoCredentialsProvider.create()).build();
+          EchoSettings.newBuilder()
+              .setCredentialsProvider(NoCredentialsProvider.create())
+              .setEndpoint(SHOWCASE_DEFAULT_ENDPOINT)
+              .build();
       echoClient = EchoClient.create(echoSettings);
       Truth.assertThat(echoClient.getSettings().getEndpoint()).isEqualTo(SHOWCASE_DEFAULT_ENDPOINT);
     } finally {

showcase/gapic-showcase/src/test/java/com/google/showcase/v1beta1/it/util/TestClientInitializer.java

@@ -213,6 +213,7 @@ public static ComplianceClient createGrpcComplianceClient(List<ClientInterceptor
                     .setChannelConfigurator(ManagedChannelBuilder::usePlaintext)
                     .setInterceptorProvider(() -> interceptorList)
                     .build())
+            .setEndpoint("localhost:7469")
             .build();
     return ComplianceClient.create(grpcComplianceSettings);
   }