Images management command to purge and regenerate renditions

Is your proposal related to a problem?

• Occasionally, you can create problems when syncing data from production environments or you just want to clear out unused renditions.
• There are also cases where there is a need to clear space on a server and we may want to intentionally only load image renditions when requested.

Describe the solution you’d like

A new management command, in the images app, that provides the ability to regenerate image renditions. With an optional argument to also purge any existing ones.

• manage.py update_image_renditions - will regenerate all the rendition images (not the DB entries)
• manage.py update_image_renditions --purge - will first purge all rendition images and then regenerate all the rendition images
• manage.py update_image_renditions --purge-only - will ONLY purge all rendition images

Describe alternatives you’ve considered

• Use something like rm -rf within the media folder, however this risks removing images that are not renditions, plus will mean that the next load for users will be slow for each image needed.

Additional context

• See the documented method of writing Django Management commands https://docs.djangoproject.com/en/4.0/howto/custom-management-commands/
• There is an old PR that started this https://github.com/wagtail/wagtail/pull/759 - could be a good reference
• There is also this PR that may be covering similar functionality https://github.com/wagtail/wagtail/pull/6595
• Use the Django documented self.stdout.write("Unterminated line", ending='') and self.stdout.write(self.style.SUCCESS('Successfully closed poll "%s"' % poll_id)) for messages, not print
• Should have documentation added to the page https://docs.wagtail.org/en/stable/reference/management_commands.html
• Needs unit tests

[lb-]

That makes sense and appears to summarise correctly @Hitansh-Shah

As noted above, feel free to start with a simple version of this that simply purges (deletes) renditions (even if that means a different name is needed.

Please also namespace the command. wagtail_update_image_renditions

See https://github.com/wagtail/wagtail/issues/8162 for context

[Hitansh-Shah]

Hey @lb- , so I looked into the resources and the requirements of this issue. So I am just confirming what I understood so far and what I am planning to do. For regenerating the renditions I will just loop through all the renditions and for each rendition I will use the get_rendition method on rendition.image with rendition.filter as the parameter (all of this in the command function obviously). This will regenerate each and every rendition. I don’t know if I have caught on to the problem, please correct me if I am wrong. If I am in the right direction do let me know so that I can open a draft Pr to work further. Thanks