add a make_cache_key parameter

[buckley-w-david]

This PR is essentially a more considered version of #76

After the additional discussion with @bzed I changed my stance on the functionality, but actually even further it seemed like what the library actually needed was a way to allow the consumer complete control over the cache key generation if they so wished.

I have added a make_cache_key parameter to the cached decorator for this purpose.

This should allow for use cases such as #71, an example of which is in the test added in this PR

[buckley-w-david]

Hmm, CI has failed some tests that are passing locally for me, I guess I'll have to figure out why first

[gergelypolonkai]

Other than the failing tests, it looks good to me. Let us know if you need help with the tests, i might be able to help tomorrow (CET)

[buckley-w-david]

Thanks for the offer, but I think I'm fine to figure it out on my own, I'm able to reproduce the failures in a docker container, so I'll just debug them and then push a fix

[coveralls]

Coverage remained the same at 80.02% when pulling 8880c10 on buckley-w-david:master into b8e2fa6 on sh4nks:master.

[buckley-w-david]

I figured out the problem, but unfortunately the fix technically makes this a very small API change that could technically result in incompatibilities with previous versions.

The make_cache_key function previously set the use_request argument of _make_cache_key to False always, now it respects the caller setting that themselves. In almost all cases this will result in it working fine for anyone who was using make_cache_key previously.

There is however a case where this will break a previously valid use case, where the caller was using the make_cache_key attribute of the returned decorator for a view function that accepts an argument named use_request.

That is a very specific and probably unlikely scenario, but it is technically possible that this would now break existing code.

We'll have to decide if that's okay or not.

[buckley-w-david]

I've pushed a change so that this no longer works off of the make_cache_key attribute of the decorator and instead is simply a argument passed to the decorator.

This isn't as slick a solution as the previous one, but after thinking it over there's no real reason to break compatibility, even in a very small corner case, when it can just be done this way. Especially since if it ever did affect anyone, it would be almost impossible to debug on their part without inspecting the source of this library and really understanding what it was doing.

Also I noticed a bug in the test, so that has also been fixed.

I've edit the PR name/description to reflect this.

[buckley-w-david]

Not sure why the tests are timing out in the first memcached test, I get no problems with them on my machine

...
tests/test_backend_cache.py::TestRedisCache::test_empty_host SKIPPED                                                             [ 46%]
tests/test_backend_cache.py::TestMemcachedCache::test_generic_get_dict PASSED                                                    [ 47%]
tests/test_backend_cache.py::TestMemcachedCache::test_generic_set_get PASSED                                                     [ 47%]
tests/test_backend_cache.py::TestMemcachedCache::test_generic_get_set PASSED                                                     [ 48%]
tests/test_backend_cache.py::TestMemcachedCache::test_generic_get_many PASSED                                                    [ 48%]
tests/test_backend_cache.py::TestMemcachedCache::test_generic_set_many PASSED                                                    [ 49%]
tests/test_backend_cache.py::TestMemcachedCache::test_generic_add PASSED                                                         [ 49%]
tests/test_backend_cache.py::TestMemcachedCache::test_generic_delete PASSED                                                      [ 50%]
tests/test_backend_cache.py::TestMemcachedCache::test_generic_delete_many PASSED                                                 [ 50%]
tests/test_backend_cache.py::TestMemcachedCache::test_generic_inc_dec PASSED                                                     [ 51%]
tests/test_backend_cache.py::TestMemcachedCache::test_generic_true_false PASSED                                                  [ 51%]
tests/test_backend_cache.py::TestMemcachedCache::test_generic_timeout PASSED                                                     [ 52%]
tests/test_backend_cache.py::TestMemcachedCache::test_generic_has PASSED                                                         [ 52%]
tests/test_backend_cache.py::TestMemcachedCache::test_compat PASSED                                                              [ 53%]
tests/test_backend_cache.py::TestMemcachedCache::test_huge_timeouts PASSED                                                       [ 53%]
tests/test_backend_cache.py::TestUWSGICache::test_generic_get_dict SKIPPED                                                       [ 54%]
...

[JimCurryWang]

Wanna ask when will flask-caching merge this PR, this feature is life-saver.

[sh4nks]

Not sure why the tests are timing out in the first memcached test, I get no problems with them on my machine

...
tests/test_backend_cache.py::TestRedisCache::test_empty_host SKIPPED                                                             [ 46%]
tests/test_backend_cache.py::TestMemcachedCache::test_generic_get_dict PASSED                                                    [ 47%]
tests/test_backend_cache.py::TestMemcachedCache::test_generic_set_get PASSED                                                     [ 47%]
tests/test_backend_cache.py::TestMemcachedCache::test_generic_get_set PASSED                                                     [ 48%]
tests/test_backend_cache.py::TestMemcachedCache::test_generic_get_many PASSED                                                    [ 48%]
tests/test_backend_cache.py::TestMemcachedCache::test_generic_set_many PASSED                                                    [ 49%]
tests/test_backend_cache.py::TestMemcachedCache::test_generic_add PASSED                                                         [ 49%]
tests/test_backend_cache.py::TestMemcachedCache::test_generic_delete PASSED                                                      [ 50%]
tests/test_backend_cache.py::TestMemcachedCache::test_generic_delete_many PASSED                                                 [ 50%]
tests/test_backend_cache.py::TestMemcachedCache::test_generic_inc_dec PASSED                                                     [ 51%]
tests/test_backend_cache.py::TestMemcachedCache::test_generic_true_false PASSED                                                  [ 51%]
tests/test_backend_cache.py::TestMemcachedCache::test_generic_timeout PASSED                                                     [ 52%]
tests/test_backend_cache.py::TestMemcachedCache::test_generic_has PASSED                                                         [ 52%]
tests/test_backend_cache.py::TestMemcachedCache::test_compat PASSED                                                              [ 53%]
tests/test_backend_cache.py::TestMemcachedCache::test_huge_timeouts PASSED                                                       [ 53%]
tests/test_backend_cache.py::TestUWSGICache::test_generic_get_dict SKIPPED                                                       [ 54%]
...

I am having the same problem on my machine but when I started the tests a second time everything went fine. I believe it has something to do with the startup of the memcache server.

Thanks for this PR @buckley-w-david!

[bzed]

Thanks a lot @buckley-w-david @sh4nks @gergelypolonkai 👍