Poetry project using `project.dependencies` in `pyproject.toml` or using no dependencies: `project: `Error: key "packages" not found in dictionary`

[sin-ack]

Environment info

Bazel version: 9.0.0rc3
rules_python: 1.6.3
rules_pycross: 0.8.1

Description

I just created a Poetry project with poetry init and integrated it with rules_pycross right away. However, because I haven't started working on it, it doesn't have any dependencies yet. As a result, it appears that both raw_lock.json and lock.json in the generated repository omit the packages key, and I get the following error:

ERROR: /home/agni/.cache/bazel/_bazel_agni/72d70f606e4bf63ec51519992d448765/external/rules_pycross+/pycross/private/package_repo.bzl:198:20: An error occurred during the fetch of repository 'rules_pycross++lock_repos+project_requirements':
   Traceback (most recent call last):
        File "/home/agni/.cache/bazel/_bazel_agni/72d70f606e4bf63ec51519992d448765/external/rules_pycross+/pycross/private/package_repo.bzl", line 198, column 20, in _package_repo_impl
                packages = lock["packages"].values()
Error: key "packages" not found in dictionary

Later, I added a dependency using poetry add pyyaml, but kept getting the same error. Recent versions of Poetry seem to be using the project.dependencies section of pyproject.toml, with this syntax:

[project]
# ...
dependencies = [
    "pyyaml (>=6.0.3,<7.0.0)"
]

I changed it to be a tool.poetry.dependencies section again, and this time rules_pycross worked.

I think there's one bug and one missing feature here:

• Fix handling of zero-dependency packages.
• Handle project.dependencies in pyproject.toml.