Change response_format string literal to const

In `PlatformSubscriber`, a hardcoded `response_format` option is used,
but it's overridden by many bridges and probably more to come. This
changes it to a public const to avoid it becoming a PITA to replace all
the occurrences if we ever have to change it

Author: paulinevos

src/platform/src/Bridge/Gemini/Gemini/ModelClient.php

@@ -15,6 +15,7 @@
 use Symfony\AI\Platform\Model;
 use Symfony\AI\Platform\ModelClientInterface;
 use Symfony\AI\Platform\Result\RawHttpResult;
+use Symfony\AI\Platform\StructuredOutput\PlatformSubscriber;
 use Symfony\Component\HttpClient\EventSourceHttpClient;
 use Symfony\Contracts\HttpClient\Exception\TransportExceptionInterface;
 use Symfony\Contracts\HttpClient\HttpClientInterface;
@@ -49,10 +50,10 @@ public function request(Model $model, array|string $payload, array $options = []
             $options['stream'] ?? false ? 'streamGenerateContent' : 'generateContent',
         );
 
-        if (isset($options['response_format']['json_schema']['schema'])) {
+        if (isset($options[PlatformSubscriber::KEY_OUTPUT_STRUCTURE]['json_schema']['schema'])) {
             $options['responseMimeType'] = 'application/json';
-            $options['responseJsonSchema'] = $options['response_format']['json_schema']['schema'];
-            unset($options['response_format']);
+            $options['responseJsonSchema'] = $options[PlatformSubscriber::KEY_OUTPUT_STRUCTURE]['json_schema']['schema'];
+            unset($options[PlatformSubscriber::KEY_OUTPUT_STRUCTURE]);
         }
 
         $generationConfig = ['generationConfig' => $options];

src/platform/src/Bridge/Ollama/OllamaClient.php

@@ -15,6 +15,7 @@
 use Symfony\AI\Platform\Model;
 use Symfony\AI\Platform\ModelClientInterface;
 use Symfony\AI\Platform\Result\RawHttpResult;
+use Symfony\AI\Platform\StructuredOutput\PlatformSubscriber;
 use Symfony\Contracts\HttpClient\HttpClientInterface;
 
 /**
@@ -63,9 +64,9 @@ private function doCompletionRequest(array|string $payload, array $options = [])
         // Revert Ollama's default streaming behavior
         $options['stream'] ??= false;
 
-        if (\array_key_exists('response_format', $options) && \array_key_exists('json_schema', $options['response_format'])) {
-            $options['format'] = $options['response_format']['json_schema']['schema'];
-            unset($options['response_format']);
+        if (\array_key_exists(PlatformSubscriber::KEY_OUTPUT_STRUCTURE, $options) && \array_key_exists('json_schema', $options[PlatformSubscriber::KEY_OUTPUT_STRUCTURE])) {
+            $options['format'] = $options[PlatformSubscriber::KEY_OUTPUT_STRUCTURE]['json_schema']['schema'];
+            unset($options[PlatformSubscriber::KEY_OUTPUT_STRUCTURE]);
         }
 
         return new RawHttpResult($this->httpClient->request('POST', \sprintf('%s/api/chat', $this->hostUrl), [

src/platform/src/Bridge/OpenAi/DallE/ResultConverter.php

@@ -17,6 +17,7 @@
 use Symfony\AI\Platform\Result\RawResultInterface;
 use Symfony\AI\Platform\Result\ResultInterface;
 use Symfony\AI\Platform\ResultConverterInterface;
+use Symfony\AI\Platform\StructuredOutput\PlatformSubscriber;
 
 /**
  * @see https://platform.openai.com/docs/api-reference/images/create
@@ -40,7 +41,7 @@ public function convert(RawResultInterface $result, array $options = []): Result
 
         $images = [];
         foreach ($result['data'] as $image) {
-            if ('url' === $options['response_format']) {
+            if ('url' === $options[PlatformSubscriber::KEY_OUTPUT_STRUCTURE]) {
                 $images[] = new UrlImage($image['url']);
 
                 continue;

src/platform/src/Bridge/VertexAi/Gemini/ModelClient.php

@@ -14,6 +14,7 @@
 use Symfony\AI\Platform\Model as BaseModel;
 use Symfony\AI\Platform\ModelClientInterface;
 use Symfony\AI\Platform\Result\RawHttpResult;
+use Symfony\AI\Platform\StructuredOutput\PlatformSubscriber;
 use Symfony\Component\HttpClient\EventSourceHttpClient;
 use Symfony\Contracts\HttpClient\Exception\TransportExceptionInterface;
 use Symfony\Contracts\HttpClient\HttpClientInterface;
@@ -51,11 +52,11 @@ public function request(BaseModel $model, array|string $payload, array $options
             $options['stream'] ?? false ? 'streamGenerateContent' : 'generateContent',
         );
 
-        if (isset($options['response_format']['json_schema']['schema'])) {
+        if (isset($options[PlatformSubscriber::KEY_OUTPUT_STRUCTURE]['json_schema']['schema'])) {
             $options['generationConfig']['responseMimeType'] = 'application/json';
-            $options['generationConfig']['responseSchema'] = $options['response_format']['json_schema']['schema'];
+            $options['generationConfig']['responseSchema'] = $options[PlatformSubscriber::KEY_OUTPUT_STRUCTURE]['json_schema']['schema'];
 
-            unset($options['response_format']);
+            unset($options[PlatformSubscriber::KEY_OUTPUT_STRUCTURE]);
         }
 
         if (isset($options['generationConfig'])) {

src/platform/src/StructuredOutput/PlatformSubscriber.php

@@ -36,6 +36,7 @@
  */
 final class PlatformSubscriber implements EventSubscriberInterface
 {
+    public const KEY_OUTPUT_STRUCTURE = 'response_format';
     private string $outputStructure;
 
     public function __construct(
@@ -91,7 +92,7 @@ public function processInput(InvocationEvent $event): void
             throw new InvalidArgumentException('Streamed responses are not supported for structured output.');
         }
 
-        $options['response_format'] = $this->responseFormatFactory->create($options['output_structure']);
+        $options[self::KEY_OUTPUT_STRUCTURE] = $this->responseFormatFactory->create($options['output_structure']);
 
         $this->outputStructure = $options['output_structure'];
         unset($options['output_structure']);
@@ -103,7 +104,7 @@ public function processResult(ResultEvent $event): void
     {
         $options = $event->getOptions();
 
-        if (!isset($options['response_format'])) {
+        if (!isset($options[self::KEY_OUTPUT_STRUCTURE])) {
             return;
         }