Signal onError instead of hanging when a reactive complex-output command errors

src/main/java/io/lettuce/core/RedisPublisher.java

@@ -761,13 +761,13 @@ protected void doOnComplete() {
 
             if (getOutput() != null) {
 
-                Object result = getOutput().get();
-
                 if (getOutput().hasError()) {
                     onError(ExceptionFactory.createExecutionException(getOutput().getError()));
                     return;
                 }
 
+                Object result = getOutput().get();
+
                 if (!(getOutput() instanceof StreamingOutput<?>) && result != null) {
 
                     if (dissolve && result instanceof Collection) {

src/test/java/io/lettuce/core/probabilistic/RedisCuckooFilterReactiveIntegrationTests.java

@@ -7,8 +7,10 @@
 package io.lettuce.core.probabilistic;
 
 import javax.inject.Inject;
+import java.time.Duration;
 import java.util.List;
 
+import io.lettuce.core.RedisCommandExecutionException;
 import io.lettuce.core.Value;
 import io.lettuce.core.api.StatefulRedisConnection;
 import io.lettuce.core.api.reactive.RedisReactiveCommands;
@@ -138,4 +140,16 @@ void cfInsertReturnsFalseWhenFilterIsFull() {
         }
     }
 
+    /**
+     * Reproduces the reactive hang on server errors: {@code RedisPublisher.SubscriptionCommand#doOnComplete()} used to call
+     * {@code getOutput().get()} before checking {@code getOutput().hasError()}, so a {@link CfInfoValueParser#parse} failure on
+     * a {@code null} payload (server error, no data) threw before the error signal could reach the subscriber, leaving the
+     * {@code Mono} hanging forever instead of erroring.
+     */
+    @Test
+    void cfInfoOnMissingKeyErrorsInsteadOfHanging() {
+        StepVerifier.create(reactive.cfInfo("does-not-exist-key")).expectError(RedisCommandExecutionException.class)
+                .verify(Duration.ofSeconds(5));
+    }
+
 }