sglang/test/srt/openai_server/features/test_json_mode.py

"""
python3 -m unittest openai_server.features.test_json_mode.TestJSONModeOutlines.test_json_mode_response
python3 -m unittest openai_server.features.test_json_mode.TestJSONModeOutlines.test_json_mode_with_streaming

python3 -m unittest openai_server.features.test_json_mode.TestJSONModeXGrammar.test_json_mode_response
python3 -m unittest openai_server.features.test_json_mode.TestJSONModeXGrammar.test_json_mode_with_streaming

python3 -m unittest openai_server.features.test_json_mode.TestJSONModeLLGuidance.test_json_mode_response
python3 -m unittest openai_server.features.test_json_mode.TestJSONModeLLGuidance.test_json_mode_with_streaming
"""

import json
import unittest

import openai

from sglang.srt.utils import kill_process_tree
from sglang.test.test_utils import (
    DEFAULT_SMALL_MODEL_NAME_FOR_TEST,
    DEFAULT_TIMEOUT_FOR_SERVER_LAUNCH,
    DEFAULT_URL_FOR_TEST,
    popen_launch_server,
)


def setup_class(cls, backend):
    cls.model = DEFAULT_SMALL_MODEL_NAME_FOR_TEST
    cls.base_url = DEFAULT_URL_FOR_TEST

    other_args = [
        "--max-running-requests",
        "10",
        "--grammar-backend",
        backend,
    ]

    cls.process = popen_launch_server(
        cls.model,
        cls.base_url,
        timeout=DEFAULT_TIMEOUT_FOR_SERVER_LAUNCH,
        other_args=other_args,
    )
    cls.client = openai.Client(api_key="EMPTY", base_url=f"{cls.base_url}/v1")


class TestJSONModeOutlines(unittest.TestCase):
    @classmethod
    def setUpClass(cls):
        setup_class(cls, "outlines")

    @classmethod
    def tearDownClass(cls):
        kill_process_tree(cls.process.pid)

    def test_json_mode_response(self):
        """Test that response_format json_object (also known as "json mode") produces valid JSON, even without a system prompt that mentions JSON."""
        response = self.client.chat.completions.create(
            model=self.model,
            messages=[
                # We are deliberately omitting "That produces JSON" or similar phrases from the assistant prompt so that we don't have misleading test results
                {
                    "role": "system",
                    "content": "You are a helpful AI assistant that gives a short answer.",
                },
                {"role": "user", "content": "What is the capital of Bulgaria?"},
            ],
            temperature=0,
            max_tokens=128,
            response_format={"type": "json_object"},
        )
        text = response.choices[0].message.content

        print(f"Response ({len(text)} characters): {text}")

        # Verify the response is valid JSON
        try:
            js_obj = json.loads(text)
        except json.JSONDecodeError as e:
            self.fail(f"Response is not valid JSON. Error: {e}. Response: {text}")

        # Verify it's actually an object (dict)
        self.assertIsInstance(js_obj, dict, f"Response is not a JSON object: {text}")

    def test_json_mode_with_streaming(self):
        """Test that streaming with json_object response (also known as "json mode") format works correctly, even without a system prompt that mentions JSON."""
        stream = self.client.chat.completions.create(
            model=self.model,
            messages=[
                # We are deliberately omitting "That produces JSON" or similar phrases from the assistant prompt so that we don't have misleading test results
                {
                    "role": "system",
                    "content": "You are a helpful AI assistant that gives a short answer.",
                },
                {"role": "user", "content": "What is the capital of Bulgaria?"},
            ],
            temperature=0,
            max_tokens=128,
            response_format={"type": "json_object"},
            stream=True,
        )

        # Collect all chunks
        chunks = []
        for chunk in stream:
            if chunk.choices[0].delta.content is not None:
                chunks.append(chunk.choices[0].delta.content)
        full_response = "".join(chunks)

        print(
            f"Concatenated Response ({len(full_response)} characters): {full_response}"
        )

        # Verify the combined response is valid JSON
        try:
            js_obj = json.loads(full_response)
        except json.JSONDecodeError as e:
            self.fail(
                f"Streamed response is not valid JSON. Error: {e}. Response: {full_response}"
            )

        self.assertIsInstance(js_obj, dict)


class TestJSONModeXGrammar(TestJSONModeOutlines):
    @classmethod
    def setUpClass(cls):
        setup_class(cls, backend="xgrammar")


class TestJSONModeLLGuidance(TestJSONModeOutlines):
    @classmethod
    def setUpClass(cls):
        setup_class(cls, backend="llguidance")


if __name__ == "__main__":
    unittest.main()