Fixed #30446 -- Resolved Value.output_field for stdlib types.

[charettes]

No description provided.

[charettes]

This still needs a bit of work when combining fields from different type (e.g. (Avg('float_field') + 2) * 3) must resolve to FloatField but right now it errors out with FieldError('Expression contains mixed types. You must set output_field.').

This last problem has a bit of overlap with #6395.

[adamchainz]

This is really cool and tidies up a bunch of use cases!

[charettes]

The last commit in the series serves more as an example of what kind of simplification this allows. It could be reverted if we want to preserve the original nature of tests, just thought it could be worth removing a bit of boilerplate.

This PR makes most of the remaining Value usages unnecessary (except for str wrapping since the ORM defaults to column references) just like explicit passing of Value(output_field). I believe it might be worth a mention in the release notes that I'm happy to write given the nice improvements of life it brings but I'll defer to the reviewers before committing to it.

I guess we could expose an API for contrib apps to register type -> output_field mapping (e.g. List[T] -> contrib.postgres.ArrayField[T]) but this can be done in a following PR/ticket.

Finally, kind of rant but I really wish we named this abstraction Literal instead of Value which doesn't really convey it's purpose and cause language gymnastic due to its vagueness (e.g. is_direct_value instead of is_literal). Not convinced we should rename it given the limited benefit it would bring at this point though.

[adamchainz]

I believe it might be worth a mention in the release notes that I'm happy to write given the nice improvements of life it brings but I'll defer to the reviewers before committing to it.

This is definitely worth mentioning with a short example. I think most Django projects end up using Value() somewhere.

I really wish we named this abstraction Literal instead of Value which doesn't really convey it's purpose

Yes Literal is a marginally better name but probably not worth the change. It would also conflict with typing.Literal if anyone uses that in the same file.

[felixxm]

@charettes Thanks 👍 I will try to first handle all cleanups. I moved the first one to the #13070.

[felixxm]

Merged two commits in ea3beb4, 5227101.

[charettes]

Thanks for the merges @felixxm I should have time to address the remaining points regarding documentation and for_save this week-end.

[charettes]

Alright pushed a commit that restored the for_save = False and details its reasoning and docs and release notes.

[charettes]

buildbot, test on oracle.

[felixxm]

I moved GIS cleanup to the #13185 and merged two cleanups in f783a99 and 9c5c9bd.

[felixxm]

@charettes Thanks 👍 I pushed small edits and removed output_field in some tests.

[charettes]

Thanks for the adjustments and merge Mariusz!