TestNoIO

test_noio.py

import itertools

from django.conf import settings
from django.http import HttpResponse
from django.template import engines
from django.utils.module_loading import import_string

import pytest


@pytest.mark.django_db
@pytest.mark.parametrize(
    "fn",
    itertools.chain(
        *(backend.engine.template_context_processors for backend in engines.all())
    ),
)
def test_no_io(fn, rf, admin_user, django_db_blocker):
    """
    Requests to redirect views MUST NOT perform any I/O operations.

    Ensure no middleware or other part of the request handling stack
    performs any I/O operations, thereby slowing down the request processing.

    A common culprit is a middleware or context_processor eagerly accessing request.user.
    """
    request = rf.get("/")
    response = HttpResponse(b"", status=200)
    with django_db_blocker.block():
        for middleware_path in settings.MIDDLEWARE:
            middleware = import_string(middleware_path)
            try:
                response = middleware(get_response=lambda req: response)(request)  # noqa: B023
            except RuntimeError:
                pytest.fail(
                    f"Middleware {middleware_path} performed I/O during request processing"
                )
        try:
            fn(request)
        except RuntimeError:
            pytest.fail(
                f"Context processor {fn.__module__}.{fn.__name__} performed I/O"
            )