Detect, and fix, template tags broken over multiple lines

[jarshwah]

Description

Template tags that are broken over multiple lines are rendered as text by DTL:

{% tagname ...
%}  <-- uh, oh! closed on a different line

It's a source of many innocuous bugs. Is this something that could be detected and fixed by djade?

[EmilStenstrom]

This is patched to work across many projects and some libraries (including django-components), so I suggest not applying this to avoid errors either way.

[adamchainz]

Yes, also there's ongoing work to add support for this to Django: https://forum.djangoproject.com/t/allow-newlines-inside-tags/36040

But a lint rule could be useful. I actually filed a duplicate the day after @jarshwah : #99.

[meshy]

This is a nice idea. It'd be great if this could detect accidental multi-line tags, and fix them.

A word of caution, though: until Django supports multi-line tags, automatic fixes should be opt-in, to make sure formatting doesn't accidentally change the semantics of a file.