flit+get_version requires all dependencies to be installed at build time

[grst]

I just noted that using get_version with flit requires all package dependencies to be installed at build time. This is because flit tries to derive the version from AST-parsing, if that fails it imports the module (and therefore all dependencies). See flit source code.

This is, for instance, annoying when building conda packages (all dependencies need to be included in the host section of meta.yml).

@flying-sheep, do you think there would be an elegant solution to this? The only thing I could think of are conditional imports in the __init__.py file, i.e. not importing dependencies when the package is imported from flit:

__init__.py

# To avoid that all dependencies need to be installed at build
# time:
import sys
if "flit" not in sys.argv[0]:
    from .foo import bar
    from .bar import foobar    

(However, in its current version, it's not very robust and might have side-effects)

[flying-sheep]

That’s even more elegant than what I came up with…

This issue is pypa/flit#253. I’m of the opinion that all dependencies should be available at build time.