Modify urls for nested routers

[merll]

drf-spectacular uses the coerce_path method of the Django Rest Framework, replacing pk path parameters with id (or the appropriate primary key). When using the drf-nested-routers library for extending URL actions to related objects, auto-generated URL paths are created with {object_pk} patterns.

Since these are not valid fields on the queryet model, they require a manual definition of URL path parameters using @extend_schema. This PR replaces such _pk suffixes with _id (or the appropriate primary key), so that further introspection is also able to guess the parameter type.

The included test is based on a manually-created URL path, since it seemed unnecessary to add nested-routers as a dependency just for this purpose.

[codecov]

Codecov Report

Merging #251 (56d9b93) into master (882ade7) will increase coverage by 0.02%.
The diff coverage is 97.43%.

@@            Coverage Diff             @@
##           master     #251      +/-   ##
==========================================
+ Coverage   98.32%   98.34%   +0.02%     
==========================================
  Files          53       53              
  Lines        4233     4539     +306     
==========================================
+ Hits         4162     4464     +302     
- Misses         71       75       +4     

Impacted Files	Coverage Δ
tests/test_extend_schema_view.py	98.57% <92.85%> (-1.43%)	⬇️
drf_spectacular/generators.py	97.28% <100.00%> (+0.73%)	⬆️
tests/test_regressions.py	99.86% <0.00%> (-0.14%)	⬇️
drf_spectacular/types.py	100.00% <0.00%> (ø)
tests/test_polymorphic.py	100.00% <0.00%> (ø)
drf_spectacular/serializers.py	100.00% <0.00%> (ø)
tests/contrib/test_django_filters.py	100.00% <0.00%> (ø)
drf_spectacular/openapi.py	96.29% <0.00%> (+0.40%)	⬆️
drf_spectacular/utils.py	99.53% <0.00%> (+0.82%)	⬆️
... and 2 more

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[kingy04]

@tfranzel Can we look at having this merged?, i am also hitting this issue. Many thanks

[tfranzel]

i'm sorry that this fell off the waggon. i had an issue with some aspects and wasn't able to follow up on it. will give it another go

[tfranzel]

sry this took so long, but as you probably figured yourself this is more complicated than it looks. i had to rebuild the change myself to get a decent understanding on whats going on here.

• this only works for one extra variable not multiple, which looks common if you use that lib. readme example
• rel_model turns out to not be the related model but the viewset model, thus ref_pk_name is also not correct.
• the distinction that is made in the orig. coerce_path with getting the pk field_name does not apply to relations, thus usage of get_pk_name there makes no sense.
• on that note, the _id suffix for relations is baked into django and can only be changed by changing the column name in the field. your proposal would do this: relation_xyz with xyz as the PK for the related model. afaik that is not what django is doing internally. you could say the PR is doing the right thing by accident due to the above mentioned bug.
• i prefer dedicated test for these things - not complicating the already complicated tests - unless it is covering fundamental functionality.

i prepared a separate PR #369 on top of this PR. @merll @kingy04 please review if those changes work for you. it is basically a simplification of this PR. waiting for feedback from you guys as i'm not a drf-nested-router user

[kingy04]

Thanks for spending some time on this @tfranzel, i have tested #369 and it is working well for my use case, the correct field types are showing in the schema and also any django filters are correctly showing now.