It seems that when dependency-graph support for python was implemented it was missed to read existing PEPs and thus the most important place to store requirements was missing: setup.cfg file.
Example of complex requirements in setup.cfg:
https://github.com/pyscaffold/pyscaffold/blob/master/setup.cfg -- which happens to be a very good starting template for new python libraries.
The req.txt parser should easily be re-used because the syntax is kep compatible, the only difference being that now the lists are stores in that standardized ini file.
Thanks for the feedback! I've taken your suggestion and passed it along to the appropriate teams.
I don't have an ETA on when or if this request will be implemented but this is in good hands.
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