Fix newExternalWorkflowStub on a interfaces without a WorkflowMethod (#2531)

Fix a bug causing newExternalWorkflowStub to fail on interfaces without WorkflowMethod

Author: Quinn-With-Two-Ns

temporal-sdk/src/main/java/io/temporal/internal/sync/ExternalWorkflowInvocationHandler.java

@@ -20,7 +20,7 @@ public ExternalWorkflowInvocationHandler(
       WorkflowExecution execution,
       WorkflowOutboundCallsInterceptor workflowOutboundCallsInterceptor,
       Functions.Proc1<String> assertReadOnly) {
-    this.workflowMetadata = POJOWorkflowInterfaceMetadata.newInstance(workflowInterface);
+    this.workflowMetadata = POJOWorkflowInterfaceMetadata.newInstance(workflowInterface, false);
     this.stub =
         new ExternalWorkflowStubImpl(execution, workflowOutboundCallsInterceptor, assertReadOnly);
   }

temporal-sdk/src/test/java/io/temporal/workflow/ExternalWorkflowInterfaceInheritanceTest.java

@@ -0,0 +1,81 @@
+package io.temporal.workflow;
+
+import static org.junit.Assert.assertEquals;
+
+import io.temporal.api.common.v1.WorkflowExecution;
+import io.temporal.client.WorkflowClient;
+import io.temporal.client.WorkflowOptions;
+import io.temporal.client.WorkflowStub;
+import io.temporal.testing.internal.SDKTestWorkflowRule;
+import java.time.Duration;
+import org.junit.Rule;
+import org.junit.Test;
+
+public class ExternalWorkflowInterfaceInheritanceTest {
+
+  @Rule
+  public SDKTestWorkflowRule testWorkflowRule =
+      SDKTestWorkflowRule.newBuilder()
+          .setWorkflowTypes(TargetWorkflowImpl.class, SignalerWorkflowImpl.class)
+          .build();
+
+  @Test
+  public void testSignalWithParentInterface() {
+    WorkflowOptions options =
+        WorkflowOptions.newBuilder()
+            .setWorkflowRunTimeout(Duration.ofSeconds(30))
+            .setWorkflowTaskTimeout(Duration.ofSeconds(2))
+            .setTaskQueue(testWorkflowRule.getTaskQueue())
+            .build();
+    TargetWorkflow target =
+        testWorkflowRule.getWorkflowClient().newWorkflowStub(TargetWorkflow.class, options);
+    WorkflowExecution execution = WorkflowClient.start(target::execute);
+
+    SignalerWorkflow signaler =
+        testWorkflowRule.newWorkflowStubTimeoutOptions(SignalerWorkflow.class);
+    signaler.execute(execution.getWorkflowId());
+
+    String result = WorkflowStub.fromTyped(target).getResult(String.class);
+    assertEquals("retried", result);
+  }
+
+  public interface Retryable {
+    @SignalMethod
+    void retryNow();
+  }
+
+  @WorkflowInterface
+  public interface TargetWorkflow extends Retryable {
+    @WorkflowMethod
+    String execute();
+  }
+
+  public static class TargetWorkflowImpl implements TargetWorkflow {
+    private String status = "started";
+
+    @Override
+    public String execute() {
+      Workflow.await(() -> status.equals("retried"));
+      return status;
+    }
+
+    @Override
+    public void retryNow() {
+      status = "retried";
+    }
+  }
+
+  @WorkflowInterface
+  public interface SignalerWorkflow {
+    @WorkflowMethod
+    void execute(String workflowId);
+  }
+
+  public static class SignalerWorkflowImpl implements SignalerWorkflow {
+    @Override
+    public void execute(String workflowId) {
+      Retryable stub = Workflow.newExternalWorkflowStub(Retryable.class, workflowId);
+      stub.retryNow();
+    }
+  }
+}