[Bugfix] Pass json-schema to GuidedDecodingParams and make test stronger (#9530)

tests/entrypoints/openai/test_chat.py

@@ -851,14 +851,28 @@ async def test_response_format_json_object(client: openai.AsyncOpenAI):
 
 @pytest.mark.asyncio
 async def test_response_format_json_schema(client: openai.AsyncOpenAI):
+    prompt = 'what is 1+1? The format is "result": 2'
+    # Check that this prompt cannot lead to a valid JSON without json_schema
     for _ in range(2):
         resp = await client.chat.completions.create(
             model=MODEL_NAME,
             messages=[{
-                "role":
-                "user",
-                "content": ('what is 1+1? please respond with a JSON object, '
-                            'the format is {"result": 2}')
+                "role": "user",
+                "content": prompt
+            }],
+        )
+        content = resp.choices[0].message.content
+        assert content is not None
+        with pytest.raises((json.JSONDecodeError, AssertionError)):
+            loaded = json.loads(content)
+            assert loaded == {"result": 2}, loaded
+
+    for _ in range(2):
+        resp = await client.chat.completions.create(
+            model=MODEL_NAME,
+            messages=[{
+                "role": "user",
+                "content": prompt
             }],
             response_format={
                 "type": "json_schema",