Error Handler: on CompletionException uses getCause()

fix #2452

Author: jknack

jooby/src/main/java/io/jooby/internal/handler/CompletionStageHandler.java

@@ -9,7 +9,10 @@
 import io.jooby.Route;
 
 import javax.annotation.Nonnull;
+
+import java.util.Optional;
 import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.CompletionException;
 import java.util.concurrent.CompletionStage;
 
 public class CompletionStageHandler implements LinkedHandler {
@@ -29,7 +32,11 @@ public CompletionStageHandler(Route.Handler next) {
       return ((CompletionStage) result).whenComplete((value, x) -> {
         try {
           if (x != null) {
-            ctx.sendError((Throwable) x);
+            Throwable exception = (Throwable) x;
+            if (exception instanceof CompletionException) {
+              exception = Optional.ofNullable(exception.getCause()).orElse(exception);
+            }
+            ctx.sendError(exception);
           } else {
             ctx.render(value);
           }

tests/src/test/java/io/jooby/i2452/Issue2452.java

@@ -0,0 +1,42 @@
+package io.jooby.i2452;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.util.concurrent.CompletableFuture;
+
+import org.jetbrains.annotations.NotNull;
+
+import io.jooby.Context;
+import io.jooby.ErrorHandler;
+import io.jooby.StatusCode;
+import io.jooby.WebClient;
+import io.jooby.exception.StatusCodeException;
+import io.jooby.junit.ServerTest;
+import io.jooby.junit.ServerTestRunner;
+
+public class Issue2452 {
+  @ServerTest
+  public void shouldHandleCompletableFutureError(ServerTestRunner runner) {
+    runner.define(app -> {
+      app.get("/2452", ctx -> CompletableFuture.supplyAsync(
+          () -> {
+            throw new StatusCodeException(StatusCode.NOT_FOUND);
+          }
+      ));
+
+      app.error((ctx, cause, code) -> {
+        ctx.setResponseCode(code);
+        ctx.send(cause.getClass().getSimpleName());
+      });
+    }).ready((WebClient http) -> {
+
+      http
+          .get("/2452", rsp -> {
+            assertEquals("StatusCodeException",
+                rsp.body().string());
+            assertEquals(StatusCode.NOT_FOUND.value(),
+                rsp.code());
+          });
+    });
+  }
+}