Native `pyproject.toml` configuration

[kieran-ryan]

What's the problem this feature will solve?

Provide native support for toml configuration to avail of rich types (and associated editor support), improve alignment across Python tooling; and remove a dependency on two configuration formats (toml & ini) within projects.

Describe the solution you'd like

Native toml support with a standalone pytest.toml and a [tool.pytest] section in pyproject.toml (PEP-518) - with the latter outlined as the intent within pytest configuration documentation.

One might wonder why [tool.pytest.ini_options] instead of [tool.pytest] as is the case with other tools

The reason is that the pytest team intends to fully utilize the rich TOML data format for configuration in the future, reserving the [tool.pytest] table for that. The ini_options table is being used, for now, as a bridge between the existing .ini configuration system and the future configuration format.

Alternative Solutions

Use INI configuration embedded within TOML through the [tool.pytest.ini_options] section within pyproject.toml.

Additional context

• implement support for PEP-518 - the tool.pytest key in pyproject.toml #1556
• deprecate setup.cfg support #3523
• xfail_strict has no effect in [tool.pytest] #3675
• Inheritable pytest configuration #13173
• tox implementation 1 October 2024 (native pyproject.toml config tox-dev/tox#999) - migrating from a legacy_tox_ini key within a [tool.tox] section. Note: yet to have full parity with all capabilities provided by the ini alternative.

Creating as unable to locate an associated open issue; feel free to close should one exist.