How to implement custom build?

[brandon-leapyear]

• I have searched the issues of this repo and believe that this is not a duplicate.

Issue

Does poetry use the [build-system] section in pyproject.toml? I see it parsed in PyProjectTOML, but I don't see anything in poetry or poetry-core using that property.

I do see tool.poetry.build, which is used in WheelBuilder, but it isn't documented:

• poetry/tests/fixtures/extended_project_without_setup/pyproject.toml

  Lines 23 to 25 in b753aaf

  	[tool.poetry.build]
  	script = "build.py"
  	generate-setup-file = false

• https://python-poetry.org/docs/pyproject/

Ideally, I would want to be able to run poetry build -f wheel using a custom build.py backend (that does some actions before calling the usual build in poetry-core) with some version of:

# pyproject.toml
[build-system]
backend-path = ["."]
build-backend = "build"

If poetry doesn't use [build-system], why not? What should be used instead? Is tool.poetry.build the way to define a custom build? If so, why isn't it documented?

Related issues:

• poetry build -f wheel broken for C extensions #1332
  • Since this issue is closed, does that mean poetry does support building wheels with C extensions? Are the docs here outdated, saying only pure python wheels are supported?
• Poetry build does not install build dependencies (affects both install and build) #2789

[Secrus]

There are plans to add support for different build backends, but for now, there is no stable or documented API for that. You can try looking at Pendulum, it uses some hacks and build.py script to build C extensions.

[abn]

This is a duplicate of #2740 #5539. Also see #5401.

I suspect you are not really looking for "build-system". This section is not directly used by Poetry. It is used by PEP 517 front ends like pypa/build or pip.

[github-actions]

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