Correctly support custom gettext output templates

[jmbowman]

Subject: Correctly support custom gettext output templates

Feature or Bugfix

• Bugfix

Purpose

Resolves #10832 by allowing message.pot.jinja to be overridden by a custom template in the configured templates path. This allows output customization to be done once in the template rather than manually for each file every time the set of strings to be translated is updated.

Detail

• To satisfy mypy, the type of the template_path parameter in GettextRenderer had to be updated to match that of its parent class.

Relates

• Local GNU gettext template (message.pot.jinja) not used #10832 (the template file was renamed after the ticket was written)

[jayaddison]

This generally seems good to me - it allows projects to customize their gettext POT output when templates_path is configured for the project (by copying/placing and updating an appropriate message.pot.jinja file in one of those directories).

The difference-in-behaviour for gettext handling of templates_path -- the fact it will fallback automatically to the built-in Sphinx message.pot.jinja template -- I think is acceptable. Without that behaviour, many gettext builds would begin failing due to missing message.pot.jinja files.

I'll review again in a few days while thinking about any other side-effects and/or migration considerations.

[jayaddison]

I'm still OK with these changes as-is; no additional thoughts/concerns in the past couple of days.

cc @n-peugnet in case you have any feedback, from your experience with i18n topics?

[n-peugnet]

cc @n-peugnet in case you have any feedback, from your experience with i18n topics?

I don't have much experience with this specific part (the gettext extractor), but this is a useful feature that I already wished I could use.
The code, docs and test seems OK to me.

[jayaddison]

👍