gh-133346: Make theming support in _colorize extensible

[ambv]

See issue for design details.

• Issue: Theming support for _colorize #133346

[ambv]

I'm a little sad about this but currently Python typing cannot construct a type that is "a set of string literals from this type's attributes" and I didn't feel like repeating myself in _colorize.

[pablogsal]

:(

[hugovk]

Thanks, it's much nicer to specify semantic meanings rather than colours in the code.

[pablogsal]

This LGTM I left some comments and questions but nothing blocking.

I have a request though: I think we should explore offering some semi-final non-experimental way to support this in 3.14 with proper documentation. If @hugovk is fine with this, I would like to propose a discussion in an issue and maybe with the SC. I don't particularly thing this needs a PEP by any means (my personal opinion non SC hat on) but I think that releasing 3.14 with colorize.set_theme() with the docs being a comment is not great and maybe it is worth an exception.

[hugovk]

I have a request though: I think we should explore offering some semi-final non-experimental way to support this in 3.14 with proper documentation. If @hugovk is fine with this, I would like to propose a discussion in an issue and maybe with the SC. I don't particularly thing this needs a PEP by any means (my personal opinion non SC hat on) but I think that releasing 3.14 with colorize.set_theme() with the docs being a comment is not great and maybe it is worth an exception.

Fine by me.

[tomasr8]

Exciting stuff! Json changes look good 🙂

[danielhollas]

It's a little unfortunate for import times that this will bring a dependency on dataclasses module to all modules that import this. :-(