interpret [] as all partitions for asign as well

src/Consumer/KafkaConsumerBuilder.php

@@ -124,6 +124,8 @@ public function withAdditionalSubscription(
         array $partitions = [],
         int $offset = self::OFFSET_STORED
     ): KafkaConsumerBuilderInterface {
+        $this->validateSubscription($partitions, $offset);
+
         $that = clone $this;
 
         $that->topics[] = new TopicSubscription($topicName, $partitions, $offset);
@@ -145,7 +147,10 @@ public function withSubscription(
         array $partitions = [],
         int $offset = self::OFFSET_STORED
     ): KafkaConsumerBuilderInterface {
+        $this->validateSubscription($partitions, $offset);
+
         $that = clone $this;
+
         $that->topics = [new TopicSubscription($topicName, $partitions, $offset)];
 
         return $that;
@@ -359,4 +364,17 @@ private function registerCallbacks(KafkaConfiguration $conf): void
             $conf->setOffsetCommitCb($this->rebalanceCallback);
         }
     }
+
+    /**
+     * @param array $partitions
+     * @param int $offset
+     */
+    private function validateSubscription(array $partitions, int $offset): void
+    {
+        if (0 <= $offset && [] === $partitions) {
+            throw new KafkaConsumerBuilderException(
+                KafkaConsumerBuilderException::TOPIC_SUBSCRIPTION_OFFSET_WITHOUT_PARTITIONS
+            );
+        }
+    }
 }

src/Exception/KafkaConsumerBuilderException.php

@@ -9,4 +9,5 @@ class KafkaConsumerBuilderException extends \Exception
     public const NO_BROKER_EXCEPTION_MESSAGE = 'You need add at least one broker to connect to.';
     public const NO_TOPICS_EXCEPTION_MESSAGE = 'No topics defined to subscribe to.';
     public const UNSUPPORTED_CALLBACK_EXCEPTION_MESSAGE = 'The callback %s is not supported for %s';
+    public const TOPIC_SUBSCRIPTION_OFFSET_WITHOUT_PARTITIONS = 'If you define an offset for a topic subscription, partition(s) must be defined as well';
 }

tests/Unit/Consumer/KafkaConsumerBuilderTest.php

@@ -72,6 +72,17 @@ public function testSubscribeToTopic(): void
         self::isInstanceOf(TopicSubscription::class, $reflectionProperty->getValue($clone));
     }
 
+    /**
+     * @return void
+     */
+    public function testSubscribeWithOffsetWithoutPartitions(): void
+    {
+        self::expectException(KafkaConsumerBuilderException::class);
+        self::expectExceptionMessage(KafkaConsumerBuilderException::TOPIC_SUBSCRIPTION_OFFSET_WITHOUT_PARTITIONS);
+
+       $this->kafkaConsumerBuilder->withAdditionalSubscription('test-topic', [], 0);
+    }
+
     /**
      * @return void
      * @throws \ReflectionException