I'm posting here to raise awareness about a new Draft packaging interoperability PEP I am proposing .
This document originated from the need to implement pip issue #609 , ie improving the behavior of pip freeze in presence of distributions installed from direct URL references.
In a thread  on discuss.python.org it was suggested a new PEP was needed to standardize the recording of the required information in .dist-info.
After investigation, I found out PEP426 (now withdrawn) had a concept of source_url metadata, which almost satisfied the requirement.  is therefore a revival of source_url, with a different storage format to allow for additional use cases.
Looking forward to reading your comments.