On Tuesday, 19 February 2013, M.-A. Lemburg wrote:
The only tool in wide spread use that understands part of the 1.2 data is setuptools/distribute, but it can only understand the Requires-Dist field of that version of the spec (only because the 1.1 Requires field was deprecated) and interprets a Provides-Extra field which isn't even standard. All other 1.2 fields are ignored. setuptools/distribute still writes 1.1 meta-data.
I've never seen environment markers being used or supported in the wild.
I'm not against modernizing the format, but given that version 1.2 has been out for around 8 years now, without much following, I think we need to make the implementation bit a requirement before accepting the PEP.
The wheel project uses metadata 2.0 and environment markers - indeed, the PEP was written to formalise what wheel was implementing (specifically so that pip was happy to incorporate support). Standard library support was hampered by the difficulty of changing Distutils - an issue which may have gone away now. I agree that standard library support would be good, either via Distutils or by incorporating distlib, but I don't think it is essential for acceptance. Paul