python: Reinstate lazy imports

[bachorp]

Addresses #19635, #18144
Depends on #21352
Critical commit: 94e39d6

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@cbornet @tomplus @krjakbrjak @fa0311 @multani

[wing328]

thanks for the pr

let me know if you need help updating the samples https://github.com/OpenAPITools/openapi-generator/actions/runs/15953926978/job/44997747683?pr=21486

[bachorp]

@wing328 Done.

[wing328]

thanks. will review and try to get it merged this weekend.

is it correct to say you've used this fix in your production environment and it's working as expected?

[bachorp]

No. I have tested this of course but I'm currently not using openapi-generator in a production setting. I originally wanted this feature to generate usable bindings for the Kubernetes API (the official python client, which is based on a very old version of openapi-generator, is rather poorly maintained) but by now more comprehensive libraries exist. So I don't know whether I will actually need this feature for myself. I have the patch ready nonetheless.

[bachorp]

Maybe some of the other users who reported problems with long import times want to have a look.
@fingon @lawrence-witt @fopinappb

[fopina]

In my case, I experimented very hacky lazy imports but turned into hell dealing with LazyObject so I went with fopina/defectdojo-api-generated#21

Validate_call being the heaviest thing done during import time, I just removed all of them and living happily ever since!

[wing328]

@bachorp thanks for sharing more with us

in this case, i'll let the Python Technical Committee decides whether to accept this enhancement or not.

@cbornet @tomplus @krjakbrjak @fa0311 @multani

[multani]

I'm happy to take a look, but can we clean up the change first? It touches it seems all the generators, although only the Python generator is (should be) changed.

[wing328]

Agreed with @multani

@bachorp Can you please update this one or file a new one with just the changes related to the Python client generator?

[bachorp]

This patch in it's current form is based and dependent on #21352, so I would like to discuss that one first. @wing328 you can find me on Slack.

(I thought I had filed this one as a draft, but apparently not, sorry!)

[wing328]

update: #21352 has been merged. thank you for your contribution.

[bachorp]

This PR now has a clean base.