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pyproject.toml (PEP518), build isolation (PEP517) and optional build dependencies

See original GitHub issue

What’s the problem this feature will solve?

Projects that have build requirements and optional build requirements can not use pyproject.toml because of the build isolation.

Example (https://bitbucket.org/fluiddyn/fluidfft): depending if mpi4py is installed, MPI extensions are built or not. It’s very important to be able to install/use the package without MPI so mpi4py can not be added in build-system.requires.

If a pyproject.toml is used, we get ImportError when importing mpi4py in the setup.py even when mpi4py is installed because of the isolation! So the MPI extensions are never build.

Describe the solution you’d like

Something like this could work:

[build-system]
# Minimum requirements for the build system to execute.
requires = [
    "setuptools", "wheel", "numpy", "cython", "jinja2", "fluidpythran>=0.1.7"
]
# packages that are used during the build only if they are installed
optional = ["mpi4py", "pythran"]

Then mpi4py would be available during the build only if it is installed. We keep the advantages of the isolation (discussed in https://www.python.org/dev/peps/pep-0517/) but optional build dependencies are allowed.

Alternative Solutions

[build-system]
# Minimum requirements for the build system to execute.
requires = [
    "setuptools", "wheel", "numpy", "cython", "jinja2", "fluidpythran>=0.1.7"
]
isolation = False

Issue Analytics

State:
Created 5 years ago
Comments:48 (29 by maintainers)

Top GitHub Comments

5reactions

paugiercommented, Jan 17, 2019

Really, this option --no-isolation is not a solution for us.

I’d like to use the build-system.requires option of pyproject.toml. It would allow users to just do pip install fluidfft. Of course I don’t want to use --no-isolation because with this option, build-system.requires is not taken into account and we loose all the benefice of pyproject.toml.
We need to be able to detect in setup.py if some packages are installed and if they are installed to use them during the build.

4reactions

paugiercommented, Jan 17, 2019

Then packages with optional build dependencies CAN NOT (and won’t be able to) use pyproject.toml ?

it is a problem! it is not something completely crazy to have a try: import ... except ImportError: in a setup.py.

Note that the solution with build-system.optional seems very simple to implement.

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