Improve Caching Schema

[Archmonger]

• Use Django async caching API
  • Note: This limits us to Django 4.0+, Python 3.8+.
• Remove async_lru_cache.
  • Django's default cache engine is functionally equivalent.
• Fix Rename cache backend to "idom" #46
• Use aiofile for async file operations.
• Protect against malicious file paths (ex ../../../etc/passwd)
• Use cache versioning to invalidate old web module files stored in cache

[Archmonger]

This now uses aiofile as well, which means fetching IDOM web modules is fully async.

Should be performant enough to where we can put off #4 for a while.

[Archmonger]

I had a concept to use cache versioning to help invalidate old web module files stored in cache.

But, unfortunately this doesn't work since the temp directory names are randomized, thus we have no easily cross-platform replicable cache key.

[rmorshea]

temp directory names are randomized

By default IDOM_WEB_MODULES_DIR is a temp dir, but that can be changed. For example you could set it using appdirs. That way it would be static.

[rmorshea]

A note on changing IDOM_WEB_MODULES_DIR: since there may already be files there at the time you change the directory you should copy over any existing files into the new location.

[Archmonger]

Is the default behavior within Core to not override existing files, even if they have different contents?

If not, then I think I should hold off on implementing anything related to cache invalidation until that takes place.

[rmorshea]

The default behavior does not overwrite. The code there is a little messy though so I just put up a PR to clean that up: reactive-python/reactpy#586

[Archmonger]

Alright. I'll handle app directory stuff when reactive-python/reactpy#586 is closed and made into a PyPI release.

In that case this PR is ready for merge. You need to make Python 3.7 tests non-required on your end for that to happen though.

[rmorshea]

IDOM core can continue supporting 3.7, you'll just need to constrain the supported versions in setup.py for this package. I'll make a note of that since I missed it earlier.

[rmorshea]

@Archmonger the latest version of IDOM has been released with the changes from reactive-python/reactpy#586. Is there anything else to do here?

[Archmonger]

This PR should be feature complete, can't be merged without making 3.7 not required. I'm assuming that's in the project settings?

I'll make a separate PR to bump IDOM in here to the new version.

[rmorshea]

Feel free to merge