Tests fail with login signal receiver which posts messages

[Mitar]

I have login signal receiver which posts a message:

@dispatch.receiver(auth_signals.user_logged_in)
def user_login_message(sender, request, user, **kwargs):
    messages.success(request, _("You have been successfully logged in."))

And in tests I want to create an authenticated client:

self.client = client.Client()
self.client.login(username=self.user_username, password=self.user_password)

But this fails as messages framework is not enabled at that point in the code.

[Claude Paroz]

Confirmed, the client.login method only fakes a basic request and doesn't apply the middlewares on it, hence request._messages is not set.

In the possible solutions, I see:

• try to apply all request middlewares to the request created in login
• special-casing (like it is done for sessions): test if messages middleware is active and manually apply MessageMiddleware.process_request to the request
• accept the limitation and document it

After having written this, I see that this is a duplicate of #15179, which tries to go with the first solution I mentioned.