Use TOML syntax for tox configuration

[redeboer]

Possible since Tox v4.21.0, see https://tox.wiki/en/4.21.0/config.html#pyproject-toml-native. Example:

[tool.tox]
requires = ["tox>=4.19"]
env_list = ["3.13", "3.12", "type"]

[tool.tox.env_run_base]
description = "Run test under {base_python}"
commands = [["pytest"]]

[tool.tox.env.type]
description = "run type check on code base"
deps = ["mypy==1.11.2", "types-cachetools>=5.5.0.20240820", "types-chardet>=5.0.4.6"]
commands = [["mypy", "src{/}tox"], ["mypy", "tests"]]

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1. VSCode extension is outdated tamasfe/taplo#624
   +0
2. Merge tox.ini into pyproject.toml with legacy method #409
   5 of 18
   🔨 Maintenance 🖱️ DX +2
   
3. Set minimal tox version to v4.21.0
4. Define tox.ini to pyproject.toml converter

[redeboer]

Closing this for now until tox configs supports native TOML syntax.

[redeboer]

Since tox v4.21.0, it should be possible to merge the job definitions under tox.ini into pyproject.toml 🎉

[redeboer]

The commands key in the native pyproject.toml configuration uses nested arrays. Since we set Taplo to sort arrays, we would have to use Rules to prevent the commands key from being sorted. In .taplo.toml:

[[rule]]
include = ["**/pyproject.toml"]
keys = ["tool.tox"]

[rule.formatting]
reorder_arrays = false

Rules are a new feature in Taplo v0.9 though, which is not yet available in VS Code, see tamasfe/taplo#624. So long as that is not the case, we get situations where a configuration like

[tool.tox.env.example]
commands = [
    ["pytest", "--no-header"],
]

is autoformatted as

[tool.tox.env.example]
commands = [
    ["--no-header", "pytest"],
]