id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
28144	Add allow_overwrite kwarg to FileSystemStorage._save	Jon Prindiville	nobody	"I want to be able to construct a filesystem storage backend that will let me overwrite files while still leveraging `FileSystemStorage`.

This set of changes (https://github.com/django/django/compare/master...jonprindiville:ticket_28144) would enable that without changing any of the default behaviour of `FileSystemStorage`. In addition to the new kwarg, this adds a test for the existing ''no-overwriting'' behaviour, and a test for the newly enabled ''overwriting'' behaviour.

I'm not sure about what I should enter here for ""Version"" (could go in anywhere, really) and ""Has patch"" (I don't have a patch, but I do have a PR-able branch, linked above. I am assuming that I should wait for review here before actually submitting a PR, though)

=== HOW?

Just add an `allow_overwrite` kwarg to `FileSystemStorage._save` that a subclasser can optionally take advantage of.


=== WHY?

You can't do this in a good way today.

A piece of advice I've seen in several places (see [#refs Refs]) for creating an overwriting storage backend is to create a subclass of `FileSystemStorage` where the `get_available_name` deletes an existing file of the same name. This, in my opinion, is a sneaky use of this function, based on the name. I guess it works, but that function is not called `get_available_name_and_maybe_delete_some_stuff_also`

A less sneaky (but more race-conditiony) implementation I have seen is to have `_save` delete the existing file before calling `FileSystemStorage._save`.

One of these is deceptive and one loops forever if you're unlucky.

=== [=#refs Refs]:

Various incarnations of this ""ovewriting"" implementation:
    - django-storages, marked as deprecated (https://github.com/jschneier/django-storages/blob/1.5.2/storages/backends/overwrite.py)
    - djangosnippets (https://djangosnippets.org/snippets/976/)
    - someone's gist (https://gist.github.com/fabiomontefuscolo/1584462)
    - django-overwrite-storage (https://github.com/ckot/django-overwrite-storage/blob/master/overwrite_storage/storage.py)"	New feature	new	File uploads/storage	1.11	Normal		file storage overwrite		Unreviewed	0	0	0	0	0	0