Installation of packages with build-time dependencies fail in some cases

[mbahri]

• I am on the latest Poetry version.
• I have searched the issues of this repo and believe that this is not a duplicate.
• If an exception occurs when executing a command, I executed it again in debug mode (-vvv option).

• OS version and name: Ubuntu 20.10
• Poetry version: 1.2.0a2
• Link of a Gist with the contents of your pyproject.toml file: https://gist.github.com/mbahri/e0f084f715178a3558d61dbc69b0a619

Issue

Installation of packages that have build-time dependencies fails in some cases.

Example here: mayavi depends on numpy at build time.

$ poetry add mayavi

RuntimeError:
          Numpy is required to build Mayavi correctly, please install it first.

Pre-installing numpy:

$ poetry add numpy
$ poetry add mayavi

RuntimeError:
          Numpy is required to build Mayavi correctly, please install it first.

Other example:

$ poetry add POT

Installation crashes due to being unable to import cython

pre-installing cython:

$ poetry add cython
$ poetry add POT

Installation crashes due to being unable to import cython

This problem seems to depend on the version of python used for the project. The POT examples both work fine with Python 3.7 but crash with Python 3.9. However:

$ poetry shell
$ pip install POT

Works with Python 3.9.

[finswimmer]

Hello @mbahri,

these packages doesn't provide a wheel in all cases. So it's necessary to build them from the sdist files. The build step happens in a temporary build environment. That's why you don't have success by installing the build-dependency manually. All these package doesn't provide a pyproject.toml containing build-system requirements according to PEP 518. Please report it to the maintainer of the projects.

There's nothing poetry can do here.

fin swimmer

[mbahri]

Hello @finswimmer

Thank you for the explanation, I will report the missing build-system requirements.

Do you have any idea why installation of POT works with poetry when using Python 3.7 but not with Python 3.9?

[finswimmer]

Do you have any idea why installation of POT works with poetry when using Python 3.7 but not with Python 3.9?

It looks like POT provide wheel files for python < 3.9. So there is no need to build the package.

[mbahri]

Reported the issue to both projects, thanks!

[github-actions]

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