pyproject RPM macros
====================

This is a provisional implementation of pyproject RPM macros for Fedora 30+.

These macros are useful for packaging Python projects that use the [PEP 517] `pyproject.toml` file, which specifies the package's build dependencies (including the build system, such as setuptools, flit or poetry).


Usage
-----

If your upstream sources include `pyproject.toml` and you want to use these macros, BuildRequire them:

    BuildRequires: pyproject-rpm-macros

This will bring in python3-devel, so you don't need to require python3-devel explicitly.

In order to get automatic build dependencies on Fedora 31+, run `%pyproject_buildrequires` in the `%generate_buildrequires` section:

    %generate_buildrequires
    %pyproject_buildrequires

Only build dependencies according to [PEP 517] and [PEP 518] will be added.
All other build dependencies (such as non-Python libraries or test dependencies) still need to be specified manually.

Then, build a wheel in `%build` with `%pyproject_wheel`:

    %build
    %pyproject_wheel

And install the wheel in `%install` with `%pyproject_install`:

    %install
    %pyproject_install


Adding run-time and test-time dependencies
------------------------------------------

To run tests in the `%check` section, the package's runtime dependencies
often need to also be included as build requirements.
If the project's build system supports the [`prepare-metadata-for-build-wheel`
hook](https://www.python.org/dev/peps/pep-0517/#prepare-metadata-for-build-wheel),
this can be done using the `-r` flag:

    %generate_buildrequires
    %pyproject_buildrequires -r

For projects that specify test requirements using an [`extra`
provide](https://packaging.python.org/specifications/core-metadata/#provides-extra-multiple-use),
these can be added using the `-x` flag.
For example, if upstream suggests installing test dependencies with
`pip install mypackage[testing]`, the test deps would be generated by:

    %generate_buildrequires
    %pyproject_buildrequires -r -x testing

For projects that specify test requirements in their [tox] configuration,
these can be added using the `-t` flag followed by the tox environment.
For example, if upstream suggests running the tests on Python 3.7 with `tox -e py37`,
the test deps would be generated by:

    %generate_buildrequires
    %pyproject_buildrequires -t py37

Note that `-t` implies `-r`, because tox normally assumes the package is installed
including all the runtime dependencies.

The `-t` option uses [tox-current-env]'s `--print-deps-only` behind the scenes.

[tox]: https://tox.readthedocs.io/
[tox-current-env]: https://github.com/fedora-python/tox-current-env/

Limitations
-----------

`%pyproject_install` currently installs all wheels in `$PWD`. We are working on a more explicit solution.

This macro changes shebang lines of every Python script in `%{buildroot}%{_bindir}` to `#! %{__python3} %{py3_shbang_opt}` (`#! /usr/bin/python3 -s`).
We plan to preserve existing Python flags in shebangs, but the work is not yet finished.

Extras are currently ignored.

Some valid Python version specifiers are not supported.

The `-x` flag does not yet support multiple (comma-separated) extras.

The `-t` flag does not yet support a reasonable default.

[PEP 517]: https://www.python.org/dev/peps/pep-0517/
[PEP 518]: https://www.python.org/dev/peps/pep-0518/