#23939: SessionAuthenticationMiddleware causes "Vary: Cookie" header no matter
what
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Reporter: andrewbadr | Owner: nobody
Type: Bug | Status: new
Component: contrib.auth | Version: 1.7
Severity: Normal | Resolution:
Keywords: cookies | Triage Stage: Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by carljm):
I don't think "document the limitation" is an acceptable answer here.
Adding `Vary: Cookie` unconditionally to all requests has massive
implications for caching of requests that otherwise would not vary per-
user. I know some large sites work hard to avoid `Vary: Cookie` on certain
responses in order to make them cacheable without having to cache
separately per-client.
I think `SessionAuthenticationMiddleware` should be implemented quite
differently, probably not as a middleware at all, but rather as code that
runs lazily when `request.user` is first used (that is, in the `get_user`
helper function).
We should also add a simple test somewhere in the test suite that sets up
a view which never accesses the session (or `request.user`, which
implicitly accesses the session), and then calls that view with an end-to-
end test passing through all the default middleware, and asserts that
`Vary: Cookie' is not added to its responses. These bugs are way too easy
to introduce, and we need a general test like that to prevent regressions
of this type.
--
Ticket URL: <https://code.djangoproject.com/ticket/23939#comment:4>
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