Fix 'WriteToConn' object has no attribute 'flush'

[meshy]

WriteToConn replaces stdout and stderr to capture output, but causes issues because it doesn't implement the TextIO API (as expected of sys.stdout and sys.stderr).

By stubbing the rest of the TextIO API we prevent issues with other code which uses more of the API than we had previously accounted for.

Fixes #16678

[github-actions]

According to mypy_primer, this change doesn't affect type check results on a corpus of open source code. ✅

[hauntsaninja]

Thanks for the fix!

[mattwedge]

Is there any chance this could make it into a 1.7.2 release? Or is 1.7 not really maintained any more?

[brianschubert]

@mattwedge Generally mypy doesn't backport bugfixes. Is there a reason you can't upgrade to a release that includes this fix (1.9+)?

[mattwedge]

@mattwedge Generally mypy doesn't backport bugfixes. Is there a reason you can't upgrade to a release that includes this fix (1.9+)?

It's for a Django project which uses django-stubs which as you can see at https://pypi.org/project/django-stubs/ requires that we use mypy 1.7.x for Django 4. It seems that in order to use the latest mypy we would have to upgrade to Django 5

[brianschubert]

You may have luck trying version combinations outside of the ones in that table. The latest version of that table now has this text below it, which gives some insight:

What "partial" support means, and why we don't pin to the exact Django/mypy version, is explained in
typeddjango/django-stubs#2101 (comment).

From skimming the linked discussion comment, it seems that the latest versions of django-stubs are still mostly compatible with Django 4, and should work fine with a range of mypy versions.

The reason django-stubs relies on particular versions of mypy is to guard against plugin API changes. From what I can tell, there were no plugin API changes between v1.4 and v1.11, so all versions from within that range should be equally compatible. (there was one plugin API change in v1.12, which would require using django-stubs v5.1.1 or later).