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AssertionError with middleware and TemplateResponse

See original GitHub issue

diff --git i/tests/test_templates.py w/tests/test_templates.py
index b48373e..57dee91 100644
--- i/tests/test_templates.py
+++ w/tests/test_templates.py
@@ -20,6 +20,11 @@ def test_templates(tmpdir):
     async def homepage(request):
         return templates.TemplateResponse("index.html", {"request": request})

+    @app.middleware("http")
+    async def noop(request, call_next):
+        response = await call_next(request)
+        return response
+
     client = TestClient(app)
     response = client.get("/")
     assert response.text == "<html>Hello, <a href='http://testserver/'>world</a></html>"

causes:

tests/test_templates.py:29: in test_templates
    response = client.get("/")
.venv/lib/python3.7/site-packages/requests/sessions.py:546: in get
    return self.request('GET', url, **kwargs)
starlette/testclient.py:421: in request
    json=json,
.venv/lib/python3.7/site-packages/requests/sessions.py:533: in request
    resp = self.send(prep, **send_kwargs)
.venv/lib/python3.7/site-packages/requests/sessions.py:646: in send
    r = adapter.send(request, **kwargs)
starlette/testclient.py:238: in send
    raise exc from None
starlette/testclient.py:235: in send
    loop.run_until_complete(self.app(scope, receive, send))
/usr/lib/python3.7/asyncio/base_events.py:584: in run_until_complete
    return future.result()
starlette/applications.py:134: in __call__
    await self.error_middleware(scope, receive, send)
starlette/middleware/errors.py:122: in __call__
    raise exc from None
starlette/middleware/errors.py:100: in __call__
    await self.app(scope, receive, _send)
starlette/middleware/base.py:25: in __call__
    response = await self.dispatch_func(request, self.call_next)
tests/test_templates.py:21: in noop
    response = await call_next(request)
starlette/middleware/base.py:47: in call_next
    assert message["type"] == "http.response.start"
E   AssertionError

message is {'type': 'http.response.template', 'template': <Template 'index.html'>, 'context': {'request': <starlette.requests.Request object at 0x7ff4a2d21e48>}} there.

This appears to be an issue with the test client only though. Do I understand it correctly that the “http.response.template” extension is only used with tests?

Issue Analytics

State:
Created 4 years ago
Reactions:15
Comments:14 (7 by maintainers)

Top GitHub Comments

4reactions

fgimiancommented, Oct 6, 2020

A slightly neater solution, which can be injected into any test which already has the client injected:

@pytest.fixture
def exclude_middleware():
    user_middleware = app.user_middleware.copy()
    app.user_middleware = []
    app.middleware_stack = app.build_middleware_stack()
    yield
    app.user_middleware = user_middleware
    app.middleware_stack = app.build_middleware_stack()

Keeping my fingers crossed that this problem gets fixed soon 😄

Huge thanks Fotis

4reactions

samuelcolvincommented, Apr 11, 2020

I currently have a hacky workaround for this.

Subclass Jinja2Templates and modify it to not send the context, this means you can’t test against the template context, but at least doesn’t fail. Does anyone have a better workaround than this (e.g. doesn’t involve changing anything in the application code, still allows tests with context)?

from starlette.responses import Response
from starlette.templating import Jinja2Templates as _Jinja2Templates, _TemplateResponse


class TestableJinja2Templates(_Jinja2Templates):
    def TemplateResponse(
        self,
        name: str,
        context: dict,
        status_code: int = 200,
        headers: dict = None,
        media_type: str = None,
        background=None,
    ) -> _TemplateResponse:
        if "request" not in context:
            raise ValueError('context must include a "request" key')
        template = self.get_template(name)
        return CustomTemplateResponse(
            template,
            context,
            status_code=status_code,
            headers=headers,
            media_type=media_type,
            background=background,
        )


class CustomTemplateResponse(_TemplateResponse):
    async def __call__(self, scope, receive, send) -> None:
        # context sending removed
        await Response.__call__(self, scope, receive, send)

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