22.5.0: pep517 build fails because is requires `hatch-fancy-pypi-readme` during build

[kloczek]

Looks like now hatch-fancy-pypi-readme requires its own code to pass pep517 build

+ /usr/bin/python3 -sBm build -w --no-isolation
* Getting dependencies for wheel...

ERROR Missing dependencies:
        hatch-fancy-pypi-readme>=22.4.0

Why not use during build `hatch-fancy-pypi-readme1 code from build tree? 🤔

[ofek]

Works for me:

❯ python -m build -w
* Creating virtualenv isolated environment...
* Installing packages in isolated environment... (hatch-fancy-pypi-readme>=22.4.0, hatchling)
* Getting dependencies for wheel...
* Building wheel...
Successfully built hatch_fancy_pypi_readme-22.6.0.dev0-py3-none-any.whl

[kloczek]

So you have installed in build env hatch-fancy-pypi-readme>=22.4.0.
I cannot build 22.0.4 either ..

But again: code of requires version is in build tree and many other modules is possible to build self bootstrapping (whey, build)

[ofek]

This isn't a build backend it's a plugin

[kloczek]

hatch-fancy-pypi-readme is required in exact minimum version so it cannot be used over PYTHONPATH=$PWD/src python -m build -w --no-isolation because in src/ there is no module metadata.
Other thing is that evebn after build it will be no metadata in src/ because hatchling as same as whey and poetry is not producing metadata in any other place than generated .whl archive.

It works for you because you executed build without --no-isolation which is causing that missing hatch-fancy-pypi-readme*.whl is downloaded duting build execution from pypi repo.
Try use that with --no-isolation to relay only what you have installed in build env and before that please uninstall hatch-fancy-pypi-readme module.

[hynek]

@ofek is there a way around this or is every distro gonna complain about this now? :-/

[kloczek]

No as long as you are requiring in pyprojest.toml module build needs metadata of tjose mofdules somewhere in build env. Just checked my +1k spec files with python moduls. Try to have look on buildd, calver, dbusmockandflit` code. In those cases I've managed to prepare build procedure which would not require installed in build env those moduels by use

%build
export PYTHONPATH=$PWD/src
%pyproject_wheel

or

%build
export PYTHONPATH=$PWD
%pyproject_wheel

to break self dependencies.

[hynek]

fixed by 2f17c36 💔

[ofek]

cc other Linux distro experts @musicinmybrain @frenzymadness @stefanor @hroncok

Is there really no way for a package to depend on itself? I wanted Hatchling to start using hatch-vcs so I can version using Git. Is that impossible?

[hroncok]

It should be possible to:

1. not list the self-dependency
2. use the https://peps.python.org/pep-0517/#in-tree-build-backends feature

[Czaki]

Is there really no way for a package to depend on itself

it may be possible, but such a package cannot depend on itself in build-system.requires section so in the case of hatch there should be introduced to detect plugins stored locally in the filesystem, not only installed packages.

[hroncok]

or if there is a a Python way to "register" a hatch plugin, the build backend could be set to a local script that imports the plugin, registers it and "returns" the hatch backend

[Czaki]

It looks like a place to touch: https://github.com/pypa/hatch/blob/master/backend/src/hatchling/plugin/manager.py#L97

[hroncok]

Pseudo-code:

[build-system]
requires = ["hatch"]
build-backend = "intree_plugin_loader:build"
backend-path = ["tools", "src"]

# tools/intree_plugin_loader.py

from hatchling import build as build_original
from hatch import register_plugin_xxx
__all__ = ['build']

def build(*args, **kwargs):
    register_plugin_xxx(...)
    return build_original(*args, **kwargs)