HTML responses generated by the Browsable API otherwise generate
inconsistent ETAGs -- due to the presence of CSRF tokens in the response
-- even when the API is read-only, (and as such when the response
contains no resource-modifying forms, i.e. neither POST nor PUT forms,
which might require the CSRF token).
While the template was appropriately including CSRF tokens only within
POST and PUT forms, its AJAX overlay included the CSRF token in *every*
response, regardless of whether it would be needed.
This change brings the logic of the `script` block into line with that
of the rest of the template -- and such that read-only APIs (and really
the Browsable API pages of *any* read-only resources) will not
needlessly include the CSRF token, and will now be safely cachable -- by
both back-end systems and by the user agent.
There were recent updates to the `@action` decorator calling a little more attention to the kwargs it accepts.
I thought it would be useful to also provide an example in the throttling section of how those kwargs can be used to define/override throttle_classes through the action decorator as well.
In the `to_internal_value` method of the primary key and slug related fields, `TypeError`s and `ValueError`s are caught from `self.get_queryset().get(...)` and presented to the user. This works fine for most cases, but can cause problems if the exception is coming from `self.get_queryset()` rather than from the `.get(...)`.
It means errors in the `get_queryset` method can be hidden and presented back to the user as though, for example, the input provided to the `to_internal_value` was the wrong type, whereas in reality there's a bug in the `get_queryset` method and therefore it should bubble up and be exposed as a server error.
I've decided to fix this because twice now I've had to debug why I'm seeing `invalid_type` errors from my serializer (errors like `wrong pk type - int` when the `pk` type on my model is `int`) when the real problem was a bug in my custom `get_queryset` method.
Erroring on deprecation or pending deprecation warnings means they are caught early. This will avoid the cycle of releasing with 'support for Django X', then chasing all the deprecation warnings one-by-one. Instead, when a new Django version is added to the test matrix, it will fail until all the relevant warnings are fixed. This avoids passing these warnings on to users, some of whom don't upgrade until they are all fixed.
The test suite raises warnings when tested against Python 3.9
`DeprecationWarning: NotImplemented should not be used in a boolean context`
Where `r` returns `NotImplemented` then this change returns `NotImplemented` first to avoid the comparison test.
Fixes#7417.
Fixes all these issues seen with `tox -e py38-django31`:
```
/Users/chainz/Documents/Projects/django-rest-framework/tests/test_request.py:208: RemovedInDjango40Warning: Passing None for the middleware get_response argument is deprecated.
SessionMiddleware().process_request(self.wrapped_request)
tests/test_requests_client.py: 1 test with warning
tests/test_testing.py: 4 tests with warnings
tests/test_throttling.py: 1 test with warning
tests/authentication/test_authentication.py: 4 tests with warnings
tests/browsable_api/test_browsable_api.py: 4 tests with warnings
/Users/chainz/Documents/Projects/django-rest-framework/rest_framework/authentication.py:139: RemovedInDjango40Warning: Passing None for the middleware get_response argument is deprecated.
check = CSRFCheck()
```
