Installing a python.extension_module into a venv

[8uurg]

When using meson install -C build, an extension_module marked with install: true will be installed for the global system installation, even when called from a virtualenv. From meson's source code there should exist an option python.install_env, which could be set to venv or auto to accomplish this. This option is however not configurable.

Are there any other alternatives for installing an extension module into a virtualenv?

[eli-schwartz]

I added this option in the Meson 0.62.0 development cycle, which means it does not exist yet in released versions of Meson.

You can install and test out yesterday's 0.62.0rc1 preview and see if it works for you. :)

[kaimast]

This seems to be broken now: ../meson.build:51:4: ERROR: Unknown method "install_env" in object <[PythonInstallation] holds [PythonExternalProgram]: <PythonExternalProgram 'python3' -> ['/usr/bin/python']>> of type PythonInstallation.

[eli-schwartz]

You're having the same issue as the post two above yours -- the post immediately above yours was a reference to the meson setup command line arguments indicating that what you are trying isn't supposed to work.

Meson doesn't allow you to conditionally set command line options dynamically in your build scripts. The value selected at configure time (via the command line or via a default value) is finalized and used everywhere.

Note that users might not want to install into a virtual environment so permitting it to be unconditionally overridden via a function would lead to problems anyway.

Pass -D options to meson setup instead. You can also set the default value in project(..., default_options: ['option=valuexxx']) which still allows users to set that option to something else if they really want.

[kaimast]

Oh, sorry. I figured this out right before you replied. Thank you for replying so quickly!!

I still get ../meson.build:49:26: ERROR: python.install_env cannot be set to "venv" unless you are in a venv! even though I am in a virtual environment.

[eli-schwartz]

Probably the detected Python program somehow ended up being the Python from out of the venv, e.g. it might have picked up the one that meson was installed with instead. You can enforce the correct python via a native file and meson-python does this automatically for you.

[kaimast]

meson-python seems to work. Thanks again for your help :)