fix: Return resolved endpoint from StubSettings' Builder (#2715)

gax-java/gax-grpc/src/main/java/com/google/api/gax/grpc/GrpcCallContext.java

@@ -154,12 +154,8 @@ private GrpcCallContext(
     this.retryableCodes = retryableCodes == null ? null : ImmutableSet.copyOf(retryableCodes);
     // Attempt to create an empty, non-functioning EndpointContext by default. The client will have
     // a valid EndpointContext with user configurations after the client has been initialized.
-    try {
-      this.endpointContext =
-          endpointContext == null ? EndpointContext.newBuilder().build() : endpointContext;
-    } catch (IOException ex) {
-      throw new RuntimeException(ex);
-    }
+    this.endpointContext =
+        endpointContext == null ? EndpointContext.getDefaultInstance() : endpointContext;
   }
 
   /**

gax-java/gax-httpjson/src/main/java/com/google/api/gax/httpjson/HttpJsonCallContext.java

@@ -135,12 +135,8 @@ private HttpJsonCallContext(
         defaultRetryableCodes == null ? null : ImmutableSet.copyOf(defaultRetryableCodes);
     // Attempt to create an empty, non-functioning EndpointContext by default. The client will have
     // a valid EndpointContext with user configurations after the client has been initialized.
-    try {
-      this.endpointContext =
-          endpointContext == null ? EndpointContext.newBuilder().build() : endpointContext;
-    } catch (IOException ex) {
-      throw new RuntimeException(ex);
-    }
+    this.endpointContext =
+        endpointContext == null ? EndpointContext.getDefaultInstance() : endpointContext;
   }
 
   /**

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

@@ -126,24 +126,20 @@ public abstract class ClientContext {
 
   /** Create a new ClientContext with default values */
   public static Builder newBuilder() {
-    try {
-      return new AutoValue_ClientContext.Builder()
-          .setBackgroundResources(Collections.<BackgroundResource>emptyList())
-          .setExecutor(Executors.newScheduledThreadPool(0))
-          .setHeaders(Collections.<String, String>emptyMap())
-          .setInternalHeaders(Collections.<String, String>emptyMap())
-          .setClock(NanoClock.getDefaultClock())
-          .setStreamWatchdog(null)
-          .setStreamWatchdogCheckInterval(Duration.ZERO)
-          .setTracerFactory(BaseApiTracerFactory.getInstance())
-          .setQuotaProjectId(null)
-          .setGdchApiAudience(null)
-          // Attempt to create an empty, non-functioning EndpointContext by default. This is
-          // not exposed to the user via getters/setters.
-          .setEndpointContext(EndpointContext.newBuilder().build());
-    } catch (IOException e) {
-      throw new RuntimeException(e);
-    }
+    return new AutoValue_ClientContext.Builder()
+        .setBackgroundResources(Collections.<BackgroundResource>emptyList())
+        .setExecutor(Executors.newScheduledThreadPool(0))
+        .setHeaders(Collections.<String, String>emptyMap())
+        .setInternalHeaders(Collections.<String, String>emptyMap())
+        .setClock(NanoClock.getDefaultClock())
+        .setStreamWatchdog(null)
+        .setStreamWatchdogCheckInterval(Duration.ZERO)
+        .setTracerFactory(BaseApiTracerFactory.getInstance())
+        .setQuotaProjectId(null)
+        .setGdchApiAudience(null)
+        // Attempt to create an empty, non-functioning EndpointContext by default. This is
+        // not exposed to the user via getters/setters.
+        .setEndpointContext(EndpointContext.getDefaultInstance());
   }
 
   public abstract Builder toBuilder();

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

@@ -47,12 +47,28 @@
 @InternalApi
 @AutoValue
 public abstract class EndpointContext {
+
+  private static final EndpointContext INSTANCE;
+
+  // static block initialization for exception handling
+  static {
+    try {
+      INSTANCE = EndpointContext.newBuilder().setServiceName("").build();
+    } catch (IOException e) {
+      throw new RuntimeException("Unable to create a default empty EndpointContext", e);
+    }
+  }
+
   public static final String GOOGLE_CLOUD_UNIVERSE_DOMAIN = "GOOGLE_CLOUD_UNIVERSE_DOMAIN";
   public static final String INVALID_UNIVERSE_DOMAIN_ERROR_TEMPLATE =
       "The configured universe domain (%s) does not match the universe domain found in the credentials (%s). If you haven't configured the universe domain explicitly, `googleapis.com` is the default.";
   public static final String UNABLE_TO_RETRIEVE_CREDENTIALS_ERROR_MESSAGE =
       "Unable to retrieve the Universe Domain from the Credentials.";
 
+  public static EndpointContext getDefaultInstance() {
+    return INSTANCE;
+  }
+
   /**
    * ServiceName is host URI for Google Cloud Services. It follows the format of
    * `{ServiceName}.googleapis.com`. For example, speech.googleapis.com would have a ServiceName of

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

@@ -266,6 +266,7 @@ public abstract static class Builder<
     @Nonnull private ApiTracerFactory tracerFactory;
     private boolean deprecatedExecutorProviderSet;
     private String universeDomain;
+    private final EndpointContext endpointContext;
 
     /**
      * Indicate when creating transport whether it is allowed to use mTLS endpoint instead of the
@@ -300,6 +301,9 @@ protected Builder(StubSettings settings) {
       this.switchToMtlsEndpointAllowed =
           settings.getEndpointContext().switchToMtlsEndpointAllowed();
       this.universeDomain = settings.getEndpointContext().universeDomain();
+      // Store the EndpointContext that was already created. This is used to return the state
+      // of the EndpointContext prior to any new modifications
+      this.endpointContext = settings.getEndpointContext();
     }
 
     /** Get Quota Project ID from Client Context * */
@@ -327,16 +331,22 @@ protected Builder(ClientContext clientContext) {
         this.headerProvider = new NoHeaderProvider();
         this.internalHeaderProvider = new NoHeaderProvider();
         this.clock = NanoClock.getDefaultClock();
-        this.clientSettingsEndpoint = null;
-        this.transportChannelProviderEndpoint = null;
-        this.mtlsEndpoint = null;
         this.quotaProjectId = null;
         this.streamWatchdogProvider = InstantiatingWatchdogProvider.create();
         this.streamWatchdogCheckInterval = Duration.ofSeconds(10);
         this.tracerFactory = BaseApiTracerFactory.getInstance();
         this.deprecatedExecutorProviderSet = false;
         this.gdchApiAudience = null;
+
+        this.clientSettingsEndpoint = null;
+        this.transportChannelProviderEndpoint = null;
+        this.mtlsEndpoint = null;
+        this.switchToMtlsEndpointAllowed = false;
         this.universeDomain = null;
+        // Attempt to create an empty, non-functioning EndpointContext by default. The client will
+        // have
+        // a valid EndpointContext with user configurations after the client has been initialized.
+        this.endpointContext = EndpointContext.getDefaultInstance();
       } else {
         ExecutorProvider fixedExecutorProvider =
             FixedExecutorProvider.create(clientContext.getExecutor());
@@ -365,6 +375,9 @@ protected Builder(ClientContext clientContext) {
         this.switchToMtlsEndpointAllowed =
             clientContext.getEndpointContext().switchToMtlsEndpointAllowed();
         this.universeDomain = clientContext.getEndpointContext().universeDomain();
+        // Store the EndpointContext that was already created. This is used to return the state
+        // of the EndpointContext prior to any new modifications
+        this.endpointContext = clientContext.getEndpointContext();
       }
     }
 
@@ -584,8 +597,19 @@ public ApiClock getClock() {
       return clock;
     }
 
+    /**
+     * @return the resolved endpoint when the Builder was created. If invoked after
+     *     `StubSettings.newBuilder()` is called, it will return the clientSettingsEndpoint value.
+     *     If other parameters are then set in the builder, the resolved endpoint is not
+     *     automatically updated. The resolved endpoint will only be recomputed when the
+     *     StubSettings is built again.
+     */
     public String getEndpoint() {
-      return clientSettingsEndpoint;
+      // For the `StubSettings.newBuilder()` case
+      if (endpointContext.equals(EndpointContext.getDefaultInstance())) {
+        return clientSettingsEndpoint;
+      }
+      return endpointContext.resolvedEndpoint();
     }
 
     public String getMtlsEndpoint() {

gax-java/gax/src/test/java/com/google/api/gax/rpc/testing/FakeCallContext.java

@@ -44,7 +44,6 @@
 import com.google.common.base.Preconditions;
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.ImmutableSet;
-import java.io.IOException;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
@@ -88,12 +87,8 @@ private FakeCallContext(
     this.tracer = tracer;
     this.retrySettings = retrySettings;
     this.retryableCodes = retryableCodes == null ? null : ImmutableSet.copyOf(retryableCodes);
-    try {
-      this.endpointContext =
-          endpointContext == null ? EndpointContext.newBuilder().build() : endpointContext;
-    } catch (IOException e) {
-      throw new RuntimeException(e);
-    }
+    this.endpointContext =
+        endpointContext == null ? EndpointContext.getDefaultInstance() : endpointContext;
   }
 
   public static FakeCallContext createDefault() {

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

@@ -416,17 +416,33 @@ public void universeDomainValidation_noCredentials_userSetUniverseDomain() throw
   @Test
   public void endpointResolution_defaultViaBuilder() {
     EchoSettings.Builder echoSettingsBuilder = EchoSettings.newBuilder();
-    // The getter in the builder returns the user set value. No configuration
-    // means the getter will return null
+    // `StubSettings.newBuilder()` will return the clientSettingsEndpoint
     Truth.assertThat(echoSettingsBuilder.getEndpoint()).isEqualTo(null);
   }
 
   // User configuration in Builder
   @Test
   public void endpointResolution_userConfigurationViaBuilder() {
-    String customEndpoint = "test.com:123";
     EchoSettings.Builder echoSettingsBuilder =
-        EchoSettings.newBuilder().setEndpoint(customEndpoint);
-    Truth.assertThat(echoSettingsBuilder.getEndpoint()).isEqualTo(customEndpoint);
+        EchoSettings.newBuilder().setEndpoint("test.com:123");
+    // `StubSettings.newBuilder()` will return the clientSettingsEndpoint
+    Truth.assertThat(echoSettingsBuilder.getEndpoint()).isEqualTo("test.com:123");
+  }
+
+  @Test
+  public void endpointResolution_builderBuilderBackToBuilder() throws IOException {
+    String customEndpoint = "test.com:123";
+    EchoStubSettings.Builder echoStubSettingsBuilder =
+        EchoStubSettings.newBuilder().setEndpoint(customEndpoint);
+    // `StubSettings.newBuilder()` will return the clientSettingsEndpoint
+    Truth.assertThat(echoStubSettingsBuilder.getEndpoint()).isEqualTo(customEndpoint);
+
+    // EndpointContext is recomputed when the Builder is re-built
+    EchoStubSettings echoStubSettings = echoStubSettingsBuilder.build();
+    Truth.assertThat(echoStubSettings.getEndpoint()).isEqualTo(customEndpoint);
+
+    // Calling toBuilder on StubSettings keeps the configurations the same
+    echoStubSettingsBuilder = echoStubSettings.toBuilder();
+    Truth.assertThat(echoStubSettingsBuilder.getEndpoint()).isEqualTo(customEndpoint);
   }
 }