Added the array support for text/plain

src/Response/Elasticsearch.php

@@ -24,6 +24,7 @@
 use Elastic\Transport\Serializer\CsvSerializer;
 use Elastic\Transport\Serializer\JsonSerializer;
 use Elastic\Transport\Serializer\NDJsonSerializer;
+use Elastic\Transport\Serializer\TextSerializer;
 use Elastic\Transport\Serializer\XmlSerializer;
 use Psr\Http\Message\ResponseInterface;
 
@@ -113,6 +114,10 @@ public function asArray(): array
             $this->asArray = CsvSerializer::unserialize($this->asString());
             return $this->asArray;
         }
+        if (strpos($contentType, 'text/plain') !== false) {
+            $this->asArray = [$this->asString()];
+            return $this->asArray;
+        }
         throw new UnknownContentTypeException(sprintf(
             "Cannot deserialize the reponse as array with Content-Type: %s",
             $contentType

tests/Response/ElasticsearchTest.php

@@ -200,4 +200,20 @@ public function testAccessAsObject()
 
         $this->assertEquals($array['foo'], $this->elasticsearch->foo);
     }
+
+    /**
+     * @see https://github.com/elastic/elasticsearch-php/issues/1218
+     */
+    public function testAccessAsArrayWithTextPlainResponse()
+    {
+        $msg = "This is a text/plain response";
+        $body = $this->psr17Factory->createStream($msg);
+        $this->elasticsearch->setResponse(
+            $this->response200
+                ->withBody($body)
+                ->withHeader('Content-Type', 'text/plain')
+        );
+
+        $this->assertEquals($msg, $this->elasticsearch[0]);
+    }
 }