Fix "HttpResponse" has no attribute "data" on TestCases

[XF-FW]

I have made things!

Related issues

Fixes #204

[XF-FW]

Ok, this is me trying to ensure myself, that this fix is the correct one and to help anyone reading to interpret this as well:

The root of the issue is this error:
"_MonkeyPatchedWSGIResponse" has no attribute "data"

I think it's worth mentioning that the error has changed slightly, due to changes made in typeddjango/django-stubs#925.

Anyway, we can see that the revealed type is wrong, by this partial example:

response = self.client.get(self.url, format="json")
reveal_type(self.client)  
# Revealed type is "django.test.client.Client"
# Expected type would be "rest_framework.test.APIClient"

Ok, let me put out some links here, so we can quickly check whatever I'm writing:

Here we have the definition for the different testcases classes that DRF provides:
https://github.com/encode/django-rest-framework/blob/e5fb9af0eaffde683fa0af3987085f86cf0d2640/rest_framework/test.py#L345
And the equivalent stubs:

djangorestframework-stubs/rest_framework-stubs/test.pyi

Line 82 in 61b1035

class APITransactionTestCase(testcases.TransactionTestCase):

The stubs for the parent testcase class that Django provides:
https://github.com/typeddjango/django-stubs/blob/42d8e18bf8d35482cdb4935866bd35304a74fc9d/django-stubs/test/testcases.pyi#L65

And stubs for Django's Client class:
https://github.com/typeddjango/django-stubs/blob/42d8e18bf8d35482cdb4935866bd35304a74fc9d/django-stubs/test/client.pyi#L150

Finally, for completeness, for the curious ones, this is where client is assigned to an instance of client_class
https://github.com/django/django/blob/8c0886b068ba4e224dd78104b93c9638b860b398/django/test/testcases.py#L432

Oof. I promise that's everything.
Ok, the problem here, seems to be that django-stubs declares the following:

class SimpleTestCase(unittest.TestCase):
    client_class: Type[Client] = ...
    client: Client

Client is typed as:

class Client(ClientMixin, _RequestFactory[_MonkeyPatchedWSGIResponse]):
    ...
    def request(self, **request: Any) -> _MonkeyPatchedWSGIResponse: ...

The initial error, now makes sense. It's using Django Client type for the client instance variable, instead of APIClient. Let's just check how are the stubs of APIClient defined:

from rest_framework.response import Response

...

class APIClient(APIRequestFactory, DjangoClient):
    ...
    def request(self, **kwargs: Any) -> Response: ...  # type: ignore[override]

Although it's pretty trivial knowledge, but we have our hands dirty, so,
while we're at it, we can confirm that rest_framework.response.Response has indeed a data attribute:

class Response(SimpleTemplateResponse):
    data: Any = ...
    ...

Anyway, back to reality. The problem is that we're using the parent class for the client type. This doesn't allow us to use the methods only defined in the child class. We need to narrow the type. I think that's what I did with this PR, by simply declaring client as having the narrower type.

Let's wrap this up, because this has like 100x times the size of the PR.

PS: Wrote an accompanying test.

[sobolevn]

Great explanation ;)

[sobolevn]

What about this case?

[XF-FW]

URLPatternsTestCase does not define a custom client as far as I can tell:
https://github.com/encode/django-rest-framework/blob/e5fb9af0eaffde683fa0af3987085f86cf0d2640/rest_framework/test.py#L368

[sobolevn]

Can you please check other types as well? You can use https://github.com/typeddjango/pytest-mypy-plugins#2-parametrized

[XF-FW]

Done!

[XF-FW]

Thanks for the link, btw. It was pretty helpful.

[sobolevn]

Thank you!