Deprecate abf and dot

[wjbenfold]

🚀 Pull Request

Description

See #4394

To do:

• Work out whether this is the right way to deprecate a module - the warning for abf at least currently shows up on import of fileformats, which we may want to avoid. Not sure where to put it instead though - in every function?
• Check wording of message and consider mentioning future mitigations (undo deprecation, use plugin architecture?)
• Fix doctest that's failing due to the deprecation warnings

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Consult Iris pull request check list

[pp-mo]

Looking good, but I agree we need to avoid the message when "just" importing iris.fileformats.

As with the other deprecations, I'd also like to be sure @lbdreyer had a chance to OK this.

That warning on any use of iris.fileformats happens because Iris imports abf to populate its file format handler structures.
I think it still makes sense to issue the warning whenever abf is imported, so I think the
nice way is to use a deferred import within a wrapper function.
I think I will propose something similar as a PR to your branch...

[pp-mo]

I think I will propose something

See wjbenfold#2

[wjbenfold]

I think I will propose something

See wjbenfold#2

I love the elegance of this solution

[lbdreyer]

As with the other deprecations, I'd also like to be sure @lbdreyer had a chance to OK this.

I'm fine with this. If we are happy to reverse the decision (or perhaps come up with an alternative!) should someone say they are still using it then that is fine.

[pp-mo]

hi @wjbenfold
something weird has happened here -- although you merged my suggestion wjbenfold#2 there is no change to iris.fileformats.__init__.py in the PR changed files
So I think something was wrong with the merge operation + you need to address it so we get what we need here

I think that's also why you are getting the docs-build fail :
We have a shim in all our code examples (e.g. here) that promotes warnings to errors,
just so we can ensure that our examples don't trigger any warnings

So the examples hit a deprecation warning when importing iris.fileformats, and that --> error in the docs build

[wjbenfold]

Ah, didn't pull before the rebase, will do that

[wjbenfold]

I believe that this is ready now @pp-mo

[pp-mo]

Ok now!