feat(poetry): support PEP 621 in Poetry 2.0+

[mkniewallner]

Closes #1002.
Blocked by #1007.

PR Checklist

• A description of the changes is added to the description of this PR.
• If there is a related issue, make sure it is linked to this PR.
• If you've fixed a bug or added code that should be tested, add tests!
• If you've added or modified a feature, documentation in docs is updated

Description of changes

Support PEP 621 syntax that Poetry 2.0 supports by implementing the suggested solution from #1002.

PoetryDependencyGetter now extends PEP621DependencyGetter, which makes it possible to parse PEP 621 dependencies even though a [tool.poetry] section is defined.

Whether projects actually use PEP 621 syntax or not, or only partially, allows parsing Poetry specific sections, similarly to other managers that define their own syntax for defining development dependencies, on top of PEP 621.

Specificities of the implementation

Poetry 2.0 is a bit more different than other PEP 621 managers, as per documented here, it is still possible to define dependencies under [project.dependencies] and have some specific parts of the data in [tool.poetry.dependencies] that enrich the dependencies that are defined in [project.dependencies], while disallowing defining new dependencies in [tool.poetry.dependencies].

For instance, given:

[project]
name = "foo"
dependencies = ["httpx", "urllib3==2.3.0"]

[tool.poetry.dependencies]
httpx = { git = "https://github.com/encode/httpx", tag = "0.28.0" }
mypy = "1.14.1"

[tool.poetry]
package-mode = false

• httpx from [tool.poetry.dependencies] enriches the data in httpx from [project.dependencies]
• mypy is NOT installed as a dependency at all by Poetry and simply skipped

This is handled in the changes by not extracting [tool.poetry.dependencies] section at all if there is at least one dependency defined under [poetry.dependencies], since in that case, we can assume that keys under [tool.poetry.dependencies] will only be duplicate of keys under [project.dependencies], expect for new dependencies, which are skipped by Poetry anyway, so we do not want to extract them.

Note that the documentation mentions that dynamic = ["dependencies"] could be used, but on my local tests, it did not change anything to set it or not, whether using Poetry as an environment manager or as a build system for building packages through poetry build.

Test plan

Additionally to the added unit and functional tests, I've also did some local tests on a dummy project to check Poetry's behaviour.

Documentation changes

It wasn't easy to update the documentation to highlight the new behaviour. I wasn't sure at first if we should separate Poetry into 2 "sections" in the page that lists supported package managers, one for "PEP 621" syntax and one for the legacy one, but since it's possible to mix both, I think this is less confusing overall to have everything as a subsection of "PEP 621".

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.0%. Comparing base (26511d8) to head (3dda700).
Report is 1 commits behind head on main.

Additional details and impacted files

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  Coverage   93.0%   93.0%           
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  Files         37      37           
  Lines        994     994           
  Branches      98      99    +1     
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  Hits         925     925           
  Misses        55      55           
  Partials      14      14           

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[mkniewallner]

The failing tests are unrelated to the changes, and are likely caused by the functional tests using Poetry 2.0, and failing somehow. Getting the same failure in #1004.

Funny how when random failures appear, it's often only on Windows 💀

[mkniewallner]

Alright, it took a bit of time, but CI is now fixed, so this is definitely ready for review now 😄