Ok/error protocol and failable ask #29186 (#29190)

New type StatusReply simplifies the very common use case of replying to a request with either a successful reply or an error reply which can be repetitive to define for every actor, with the additional overhead of having to make sure each such sealed top type + 2 concrete reply classes has working serialization.

akka-actor-tests/src/test/java/akka/pattern/StatusReplyTest.java

@@ -0,0 +1,123 @@
+/*
+ * Copyright (C) 2020 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package akka.pattern;
+
+import akka.actor.Actor;
+import akka.testkit.AkkaJUnitActorSystemResource;
+import akka.testkit.AkkaSpec;
+import akka.testkit.TestException;
+import akka.testkit.TestProbe;
+import org.junit.Assert;
+import org.junit.ClassRule;
+import org.junit.Test;
+import org.scalatestplus.junit.JUnitSuite;
+
+import java.time.Duration;
+import java.util.concurrent.CompletionStage;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.TimeUnit;
+
+import static akka.pattern.Patterns.askWithStatus;
+
+import static org.junit.Assert.*;
+
+public class StatusReplyTest extends JUnitSuite {
+
+  @ClassRule
+  public static AkkaJUnitActorSystemResource actorSystemResource =
+      new AkkaJUnitActorSystemResource("JavaAPI", AkkaSpec.testConf());
+
+  @Test
+  public void testSuccessApi() {
+    StatusReply<String> reply = StatusReply.success("woho");
+    assertTrue(reply.isSuccess());
+    assertFalse(reply.isError());
+    assertEquals("woho", reply.getValue());
+    try {
+      reply.getError();
+      Assert.fail("Calling get error on success did not throw");
+    } catch (IllegalArgumentException ex) {
+      // this is what we expect
+    }
+  }
+
+  @Test
+  public void testErrorMessageApi() {
+    StatusReply<String> reply = StatusReply.error("boho");
+    assertTrue(reply.isError());
+    assertFalse(reply.isSuccess());
+    assertEquals("boho", reply.getError().getMessage());
+    try {
+      reply.getValue();
+      Assert.fail("Calling get value on error did not throw");
+    } catch (StatusReply.ErrorMessage ex) {
+      // this is what we expect
+    } catch (Throwable th) {
+      Assert.fail("Unexpected exception type: " + th);
+    }
+  }
+
+  @Test
+  public void testErrorExceptionApi() {
+    StatusReply<String> reply = StatusReply.error(new TestException("boho"));
+    assertTrue(reply.isError());
+    assertFalse(reply.isSuccess());
+    assertEquals("boho", reply.getError().getMessage());
+    try {
+      reply.getValue();
+      Assert.fail("Calling get value on error did not throw");
+    } catch (TestException ex) {
+      // this is what we expect
+    } catch (Throwable th) {
+      Assert.fail("Unexpected exception type: " + th);
+    }
+  }
+
+  @Test
+  public void testAskWithStatusSuccess() throws Exception {
+    TestProbe probe = new TestProbe(actorSystemResource.getSystem());
+
+    CompletionStage<Object> response = askWithStatus(probe.ref(), "request", Duration.ofSeconds(3));
+    probe.expectMsg("request");
+    probe.lastSender().tell(StatusReply.success("woho"), Actor.noSender());
+
+    Object result = response.toCompletableFuture().get(3, TimeUnit.SECONDS);
+    assertEquals("woho", result);
+  }
+
+  @Test
+  public void testAskWithStatusErrorMessage() throws Exception {
+    TestProbe probe = new TestProbe(actorSystemResource.getSystem());
+
+    CompletionStage<Object> response = askWithStatus(probe.ref(), "request", Duration.ofSeconds(3));
+    probe.expectMsg("request");
+    probe.lastSender().tell(StatusReply.error("boho"), Actor.noSender());
+
+    try {
+      Object result = response.toCompletableFuture().get(3, TimeUnit.SECONDS);
+    } catch (ExecutionException ex) {
+      // what we expected
+      assertEquals(StatusReply.ErrorMessage.class, ex.getCause().getClass());
+      assertEquals("boho", ex.getCause().getMessage());
+    }
+  }
+
+  @Test
+  public void testAskWithStatusErrorException() throws Exception {
+    TestProbe probe = new TestProbe(actorSystemResource.getSystem());
+
+    CompletionStage<Object> response = askWithStatus(probe.ref(), "request", Duration.ofSeconds(3));
+    probe.expectMsg("request");
+    probe.lastSender().tell(StatusReply.error(new TestException("boho")), Actor.noSender());
+
+    try {
+      Object result = response.toCompletableFuture().get(3, TimeUnit.SECONDS);
+    } catch (ExecutionException ex) {
+      // what we expected
+      assertEquals(TestException.class, ex.getCause().getClass());
+      assertEquals("boho", ex.getCause().getMessage());
+    }
+  }
+}