Deploy system check that DJANGO_ALLOW_ASYNC_UNSAFE is not set

[Adam Johnson]

Django's async-safety feature disable itself if the environment variable DJANGO_ALLOW_ASYNC_UNSAFE is set to any value. This is useful for jupyter notebooks and similar, however it can lead to data loss in production.

I suggest a deploy-tagged system check that returns an error if it is set, to guard against it being used for production web traffic.

[Carlton Gibson]

OK, a deployment (--deploy ) seems reasonable.

[Andrew Godwin]

I concur that we need this!

[Adam Johnson]

Anyone picking this up see previous system checks PR's for all the places to edit: ​https://github.com/django/django/pulls?q=is%3Apr+added+check+is%3Aclosed

[hashlash]

Check DJANGO_ALLOW_ASYNC_UNSAFE on deployment implementation

[Adam Johnson]

@hashlash please make a PR on GitHub

Also I think the tag should be 'async', if we even need to add a tag.

Please also add documentation and release note.

[hashlash]

Replying to Adam (Chainz) Johnson:

Also I think the tag should be 'async', if we even need to add a tag.

Something like this?

class Tags:
    ...
    async = 'async'
    ...

But async is a reserved word in Python. Or do you mean the string part only and leave the attribute as asyncio?

class Tags:
    ...
    asyncio = 'async'
    ...

[Adam Johnson]

Forgot it's a reserved word.

I think we want to avoid 'asyncio' since that's a specific library, and in theory async stuff can move to other async libraries like curio / trio. Maybe 'asgi' is a better tag, since that's the target framework for django async stuff. Or we could use async_ = 'async' as the tag, acknowledging it's a reserved word.

[hashlash]

Replying to Adam (Chainz) Johnson:

I think we want to avoid 'asyncio' since that's a specific library, and in theory async stuff can move to other async libraries like curio / trio. Maybe 'asgi' is a better tag, since that's the target framework for django async stuff. Or we could use async_ = 'async' as the tag, acknowledging it's a reserved word.

I'll take asgi and will make the PR. Tell me if anybody has any thoughts about the naming

[hashlash]

PR: ​https://github.com/django/django/pull/12596

Haven't submitted the documentation and release note yet. Will update soon

[hashlash]

Updated in PR

[Carlton Gibson]

There's just a couple of docs comments on the PR. (Then this looks good to go.)

@hashlash: Please uncheck Needs documentation when done, to make sure we see it quickly.

Thanks!

[hashlash]

Updated in PR

[Mariusz Felisiak <felisiak.mariusz@…>]

In 4a6f2b6:

Fixed #31380 -- Added deployment system check for DJANGO_ALLOW_ASYNC_UNSAFE environment variable.