Support arbitrary json_object in OpenAI and Context Free Grammar (#3211)

tests/entrypoints/test_openai_server.py

@@ -660,5 +660,55 @@ async def test_guided_decoding_type_error(server, client: openai.AsyncOpenAI):
             extra_body=dict(guided_regex=TEST_REGEX, guided_json=TEST_SCHEMA))
 
 
+async def test_response_format_json_object(server, client: openai.AsyncOpenAI):
+    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}')
+        }],
+        response_format={"type": "json_object"})
+
+    content = resp.choices[0].message.content
+    loaded = json.loads(content)
+    assert loaded == {"result": 2}, loaded
+
+
+async def test_guided_grammar(server, client: openai.AsyncOpenAI):
+    simple_sql_grammar = """
+start: select_statement
+
+select_statement: "SELECT" column "from" table "where" condition
+
+column: "col_1" | "col_2"
+table: "table_1" | "table_2"
+condition: column "=" number
+
+number: "1" | "2"
+"""
+
+    completion = await client.completions.create(
+        model=MODEL_NAME,
+        prompt=("Generate a sql state that select col_1 from "
+                "table_1 where it is equals to 1"),
+        temperature=1.0,
+        max_tokens=500,
+        extra_body=dict(guided_grammar=simple_sql_grammar))
+
+    content = completion.choices[0].text
+
+    # use Lark to parse the output, and make sure it's a valid parse tree
+    from lark import Lark
+    parser = Lark(simple_sql_grammar)
+    parser.parse(content)
+
+    # remove spaces for comparison b/c we removed them in the grammar
+    ground_truth = "SELECT col_1 from table_1 where col_1 = 1".replace(" ", "")
+
+    assert content.strip() == ground_truth
+
+
 if __name__ == "__main__":
     pytest.main([__file__])