Bug: Using structlog's KeyValueRenderer causes an error on every message

[xeals]

Description

This is the same symptoms as #2151, but occurs with structlog.processors.KeyValueRenderer as well. Specifically it only occurs when not attached to a TTY, such as being run through nohup or a system service manager.

URL to code causing the issue

No response

MCVE

import structlog
from litestar import Litestar, Request, get
from litestar.logging import StructLoggingConfig
from litestar.plugins.structlog import StructlogConfig, StructlogPlugin

logger = structlog.get_logger()


@get("/")
async def my_router_handler(request: Request) -> None:
    logger.info("inside a request")
    return None


# Only change to base example, added two parameters to config.
logging_config = StructlogConfig(
    structlog_logging_config=StructLoggingConfig(
        processors=[structlog.processors.KeyValueRenderer()],
        log_exceptions="always",
    ),
)

app = Litestar(
    route_handlers=[my_router_handler],
    plugins=[StructlogPlugin(logging_config)],
)

Steps to reproduce

1. nohup uvicorn mvce:app
2. curl localhost:8000
3. Observe Internal Server Error and confirm backtrace in nohup.log

Screenshots

No response

Logs

ERROR:    Exception in ASGI application
Traceback (most recent call last):
  File "/nix/store/ggwbxm2ambk0ihill7r12c8vvjsiszxr-dev-env/lib/python3.13/site-packages/litestar/middleware/_internal/
exceptions/middleware.py", line 158, in __call__
    await self.app(scope, receive, capture_response_started)
  File "/nix/store/ggwbxm2ambk0ihill7r12c8vvjsiszxr-dev-env/lib/python3.13/site-packages/litestar/_asgi/asgi_router.py"
, line 100, in __call__
    await asgi_app(scope, receive, send)
  File "/nix/store/ggwbxm2ambk0ihill7r12c8vvjsiszxr-dev-env/lib/python3.13/site-packages/litestar/middleware/base.py",
line 147, in wrapped_call
    await original__call__(self, scope, receive, send)  # pyright: ignore
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/nix/store/ggwbxm2ambk0ihill7r12c8vvjsiszxr-dev-env/lib/python3.13/site-packages/litestar/middleware/logging.py
", line 110, in __call__
    await self.log_request(scope=scope, receive=receive)
  File "/nix/store/ggwbxm2ambk0ihill7r12c8vvjsiszxr-dev-env/lib/python3.13/site-packages/litestar/middleware/logging.py
", line 125, in log_request
    self.log_message(values=extracted_data)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^
  File "/nix/store/ggwbxm2ambk0ihill7r12c8vvjsiszxr-dev-env/lib/python3.13/site-packages/litestar/middleware/logging.py
", line 150, in log_message
    self.logger.info(message, **values)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^
  File "/nix/store/ggwbxm2ambk0ihill7r12c8vvjsiszxr-dev-env/lib/python3.13/site-packages/structlog/_native.py", line 16
4, in meth
    return self._proxy_to_logger(
           ~~~~~~~~~~~~~~~~~~~~~^
        name, _maybe_interpolate(event, args), **kw
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    )
    ^
  File "/nix/store/ggwbxm2ambk0ihill7r12c8vvjsiszxr-dev-env/lib/python3.13/site-packages/structlog/_base.py", line 223,
 in _proxy_to_logger
    return getattr(self._logger, method_name)(*args, **kw)
           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^
  File "/nix/store/ggwbxm2ambk0ihill7r12c8vvjsiszxr-dev-env/lib/python3.13/site-packages/structlog/_output.py", line 32
1, in msg
    self._write(message + b"\n")
                ~~~~~~~~^~~~~~~
TypeError: can only concatenate str (not "bytes") to str

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/nix/store/ggwbxm2ambk0ihill7r12c8vvjsiszxr-dev-env/lib/python3.13/site-packages/uvicorn/protocols/http/httptools_impl.py", line 409, in run_asgi
    result = await app(  # type: ignore[func-returns-value]
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        self.scope, self.receive, self.send
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    )
    ^
  File "/nix/store/ggwbxm2ambk0ihill7r12c8vvjsiszxr-dev-env/lib/python3.13/site-packages/uvicorn/middleware/proxy_heade
rs.py", line 60, in __call__
    return await self.app(scope, receive, send)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/nix/store/ggwbxm2ambk0ihill7r12c8vvjsiszxr-dev-env/lib/python3.13/site-packages/litestar/app.py", line 623, in
 __call__
    await self.asgi_handler(scope, receive, self._wrap_send(send=send, scope=scope))  # type: ignore[arg-type]
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/nix/store/ggwbxm2ambk0ihill7r12c8vvjsiszxr-dev-env/lib/python3.13/site-packages/litestar/middleware/_internal/
exceptions/middleware.py", line 166, in __call__
    self.handle_exception_logging(logger=logger, logging_config=litestar_app.logging_config, scope=scope)
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/nix/store/ggwbxm2ambk0ihill7r12c8vvjsiszxr-dev-env/lib/python3.13/site-packages/litestar/middleware/_internal/
exceptions/middleware.py", line 270, in handle_exception_logging
    logging_config.exception_logging_handler(logger, scope, format_exception(*exc))
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/nix/store/ggwbxm2ambk0ihill7r12c8vvjsiszxr-dev-env/lib/python3.13/site-packages/litestar/logging/config.py", l
ine 137, in _default_exception_logging_handler
    logger.exception(
    ~~~~~~~~~~~~~~~~^
        "Uncaught exception",
        ^^^^^^^^^^^^^^^^^^^^^
        connection_type=scope["type"],
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        path=scope["path"],
        ^^^^^^^^^^^^^^^^^^^
    )
    ^
  File "/nix/store/ggwbxm2ambk0ihill7r12c8vvjsiszxr-dev-env/lib/python3.13/site-packages/structlog/_native.py", line 47
, in exception
    return self.error(event, *args, **kw)
           ~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^
  File "/nix/store/ggwbxm2ambk0ihill7r12c8vvjsiszxr-dev-env/lib/python3.13/site-packages/structlog/_native.py", line 16
4, in meth
    return self._proxy_to_logger(
           ~~~~~~~~~~~~~~~~~~~~~^
        name, _maybe_interpolate(event, args), **kw
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    )
    ^
  File "/nix/store/ggwbxm2ambk0ihill7r12c8vvjsiszxr-dev-env/lib/python3.13/site-packages/structlog/_base.py", line 223, in _proxy_to_logger
    return getattr(self._logger, method_name)(*args, **kw)
           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^
  File "/nix/store/ggwbxm2ambk0ihill7r12c8vvjsiszxr-dev-env/lib/python3.13/site-packages/structlog/_output.py", line 321, in msg
    self._write(message + b"\n")
                ~~~~~~~~^~~~~~~
TypeError: can only concatenate str (not "bytes") to str

Litestar Version

2.19.0

Platform

• Linux
• Mac
• Windows
• Other (Please specify in the description above)