claude-code-sdk-python/tests/test_subprocess_buffering.py

"""Tests for subprocess transport buffering edge cases."""

import json
from collections.abc import AsyncIterator
from typing import Any
from unittest.mock import AsyncMock, MagicMock

import anyio
import pytest

from claude_agent_sdk._errors import CLIJSONDecodeError
from claude_agent_sdk._internal.transport.subprocess_cli import (
    _DEFAULT_MAX_BUFFER_SIZE,
    SubprocessCLITransport,
)
from claude_agent_sdk.types import ClaudeAgentOptions

DEFAULT_CLI_PATH = "/usr/bin/claude"


def make_options(**kwargs: object) -> ClaudeAgentOptions:
    """Construct ClaudeAgentOptions with a default CLI path for tests."""

    cli_path = kwargs.pop("cli_path", DEFAULT_CLI_PATH)
    return ClaudeAgentOptions(cli_path=cli_path, **kwargs)


class MockTextReceiveStream:
    """Mock TextReceiveStream for testing."""

    def __init__(self, lines: list[str]) -> None:
        self.lines = lines
        self.index = 0

    def __aiter__(self) -> AsyncIterator[str]:
        return self

    async def __anext__(self) -> str:
        if self.index >= len(self.lines):
            raise StopAsyncIteration
        line = self.lines[self.index]
        self.index += 1
        return line


class TestSubprocessBuffering:
    """Test subprocess transport handling of buffered output."""

    def test_multiple_json_objects_on_single_line(self) -> None:
        """Test parsing when multiple JSON objects are concatenated on a single line.

        In some environments, stdout buffering can cause multiple distinct JSON
        objects to be delivered as a single line with embedded newlines.
        """

        async def _test() -> None:
            json_obj1 = {"type": "message", "id": "msg1", "content": "First message"}
            json_obj2 = {"type": "result", "id": "res1", "status": "completed"}

            buffered_line = json.dumps(json_obj1) + "\n" + json.dumps(json_obj2)

            transport = SubprocessCLITransport(prompt="test", options=make_options())

            mock_process = MagicMock()
            mock_process.returncode = None
            mock_process.wait = AsyncMock(return_value=None)
            transport._process = mock_process

            transport._stdout_stream = MockTextReceiveStream([buffered_line])  # type: ignore[assignment]
            transport._stderr_stream = MockTextReceiveStream([])  # type: ignore[assignment]

            messages: list[Any] = []
            async for msg in transport.read_messages():
                messages.append(msg)

            assert len(messages) == 2
            assert messages[0]["type"] == "message"
            assert messages[0]["id"] == "msg1"
            assert messages[0]["content"] == "First message"
            assert messages[1]["type"] == "result"
            assert messages[1]["id"] == "res1"
            assert messages[1]["status"] == "completed"

        anyio.run(_test)

    def test_json_with_embedded_newlines(self) -> None:
        """Test parsing JSON objects that contain newline characters in string values."""

        async def _test() -> None:
            json_obj1 = {"type": "message", "content": "Line 1\nLine 2\nLine 3"}
            json_obj2 = {"type": "result", "data": "Some\nMultiline\nContent"}

            buffered_line = json.dumps(json_obj1) + "\n" + json.dumps(json_obj2)

            transport = SubprocessCLITransport(prompt="test", options=make_options())

            mock_process = MagicMock()
            mock_process.returncode = None
            mock_process.wait = AsyncMock(return_value=None)
            transport._process = mock_process
            transport._stdout_stream = MockTextReceiveStream([buffered_line])
            transport._stderr_stream = MockTextReceiveStream([])

            messages: list[Any] = []
            async for msg in transport.read_messages():
                messages.append(msg)

            assert len(messages) == 2
            assert messages[0]["content"] == "Line 1\nLine 2\nLine 3"
            assert messages[1]["data"] == "Some\nMultiline\nContent"

        anyio.run(_test)

    def test_multiple_newlines_between_objects(self) -> None:
        """Test parsing with multiple newlines between JSON objects."""

        async def _test() -> None:
            json_obj1 = {"type": "message", "id": "msg1"}
            json_obj2 = {"type": "result", "id": "res1"}

            buffered_line = json.dumps(json_obj1) + "\n\n\n" + json.dumps(json_obj2)

            transport = SubprocessCLITransport(prompt="test", options=make_options())

            mock_process = MagicMock()
            mock_process.returncode = None
            mock_process.wait = AsyncMock(return_value=None)
            transport._process = mock_process
            transport._stdout_stream = MockTextReceiveStream([buffered_line])
            transport._stderr_stream = MockTextReceiveStream([])

            messages: list[Any] = []
            async for msg in transport.read_messages():
                messages.append(msg)

            assert len(messages) == 2
            assert messages[0]["id"] == "msg1"
            assert messages[1]["id"] == "res1"

        anyio.run(_test)

    def test_split_json_across_multiple_reads(self) -> None:
        """Test parsing when a single JSON object is split across multiple stream reads."""

        async def _test() -> None:
            json_obj = {
                "type": "assistant",
                "message": {
                    "content": [
                        {"type": "text", "text": "x" * 1000},
                        {
                            "type": "tool_use",
                            "id": "tool_123",
                            "name": "Read",
                            "input": {"file_path": "/test.txt"},
                        },
                    ]
                },
            }

            complete_json = json.dumps(json_obj)

            part1 = complete_json[:100]
            part2 = complete_json[100:250]
            part3 = complete_json[250:]

            transport = SubprocessCLITransport(prompt="test", options=make_options())

            mock_process = MagicMock()
            mock_process.returncode = None
            mock_process.wait = AsyncMock(return_value=None)
            transport._process = mock_process
            transport._stdout_stream = MockTextReceiveStream([part1, part2, part3])
            transport._stderr_stream = MockTextReceiveStream([])

            messages: list[Any] = []
            async for msg in transport.read_messages():
                messages.append(msg)

            assert len(messages) == 1
            assert messages[0]["type"] == "assistant"
            assert len(messages[0]["message"]["content"]) == 2

        anyio.run(_test)

    def test_large_minified_json(self) -> None:
        """Test parsing a large minified JSON (simulating the reported issue)."""

        async def _test() -> None:
            large_data = {"data": [{"id": i, "value": "x" * 100} for i in range(1000)]}
            json_obj = {
                "type": "user",
                "message": {
                    "role": "user",
                    "content": [
                        {
                            "tool_use_id": "toolu_016fed1NhiaMLqnEvrj5NUaj",
                            "type": "tool_result",
                            "content": json.dumps(large_data),
                        }
                    ],
                },
            }

            complete_json = json.dumps(json_obj)

            chunk_size = 64 * 1024
            chunks = [
                complete_json[i : i + chunk_size]
                for i in range(0, len(complete_json), chunk_size)
            ]

            transport = SubprocessCLITransport(prompt="test", options=make_options())

            mock_process = MagicMock()
            mock_process.returncode = None
            mock_process.wait = AsyncMock(return_value=None)
            transport._process = mock_process
            transport._stdout_stream = MockTextReceiveStream(chunks)
            transport._stderr_stream = MockTextReceiveStream([])

            messages: list[Any] = []
            async for msg in transport.read_messages():
                messages.append(msg)

            assert len(messages) == 1
            assert messages[0]["type"] == "user"
            assert (
                messages[0]["message"]["content"][0]["tool_use_id"]
                == "toolu_016fed1NhiaMLqnEvrj5NUaj"
            )

        anyio.run(_test)

    def test_buffer_size_exceeded(self) -> None:
        """Test that exceeding buffer size raises an appropriate error."""

        async def _test() -> None:
            huge_incomplete = '{"data": "' + "x" * (_DEFAULT_MAX_BUFFER_SIZE + 1000)

            transport = SubprocessCLITransport(prompt="test", options=make_options())

            mock_process = MagicMock()
            mock_process.returncode = None
            mock_process.wait = AsyncMock(return_value=None)
            transport._process = mock_process
            transport._stdout_stream = MockTextReceiveStream([huge_incomplete])
            transport._stderr_stream = MockTextReceiveStream([])

            with pytest.raises(Exception) as exc_info:
                messages: list[Any] = []
                async for msg in transport.read_messages():
                    messages.append(msg)

            assert isinstance(exc_info.value, CLIJSONDecodeError)
            assert "exceeded maximum buffer size" in str(exc_info.value)

        anyio.run(_test)

    def test_buffer_size_option(self) -> None:
        """Test that the configurable buffer size option is respected."""

        async def _test() -> None:
            custom_limit = 512
            huge_incomplete = '{"data": "' + "x" * (custom_limit + 10)

            transport = SubprocessCLITransport(
                prompt="test",
                options=make_options(max_buffer_size=custom_limit),
            )

            mock_process = MagicMock()
            mock_process.returncode = None
            mock_process.wait = AsyncMock(return_value=None)
            transport._process = mock_process
            transport._stdout_stream = MockTextReceiveStream([huge_incomplete])
            transport._stderr_stream = MockTextReceiveStream([])

            with pytest.raises(CLIJSONDecodeError) as exc_info:
                async for _ in transport.read_messages():
                    pass

            assert f"maximum buffer size of {custom_limit} bytes" in str(exc_info.value)

        anyio.run(_test)

    def test_mixed_complete_and_split_json(self) -> None:
        """Test handling a mix of complete and split JSON messages."""

        async def _test() -> None:
            msg1 = json.dumps({"type": "system", "subtype": "start"})

            large_msg = {
                "type": "assistant",
                "message": {"content": [{"type": "text", "text": "y" * 5000}]},
            }
            large_json = json.dumps(large_msg)

            msg3 = json.dumps({"type": "system", "subtype": "end"})

            lines = [
                msg1 + "\n",
                large_json[:1000],
                large_json[1000:3000],
                large_json[3000:] + "\n" + msg3,
            ]

            transport = SubprocessCLITransport(prompt="test", options=make_options())

            mock_process = MagicMock()
            mock_process.returncode = None
            mock_process.wait = AsyncMock(return_value=None)
            transport._process = mock_process
            transport._stdout_stream = MockTextReceiveStream(lines)
            transport._stderr_stream = MockTextReceiveStream([])

            messages: list[Any] = []
            async for msg in transport.read_messages():
                messages.append(msg)

            assert len(messages) == 3
            assert messages[0]["type"] == "system"
            assert messages[0]["subtype"] == "start"
            assert messages[1]["type"] == "assistant"
            assert len(messages[1]["message"]["content"][0]["text"]) == 5000
            assert messages[2]["type"] == "system"
            assert messages[2]["subtype"] == "end"

        anyio.run(_test)