PEP 806: Mixed sync/async context managers with precise async marking

[Zac-HD]

With thanks to everyone who I've discussed this with; especially to Rob Rolls on Discuss for the ultimate proposal here, and to Jelle for offering to sponsor the PEP here.

Basic requirements (all PEP Types)

• Read and followed PEP 1 & PEP 12
• File created from the latest PEP template
• PEP has next available number, & set in filename (pep-NNNN.rst), PR title (PEP 123: <Title of PEP>) and PEP header
• Title clearly, accurately and concisely describes the content in 79 characters or less
• Core dev/PEP editor listed as Author or Sponsor, and formally confirmed their approval
• Author, Status (Draft), Type and Created headers filled out correctly
• PEP-Delegate, Topic, Requires and Replaces headers completed if appropriate
• Required sections included
  • Abstract (first section)
  • Copyright (last section; exact wording from template required)
• Code is well-formatted (PEP 7/PEP 8) and is in code blocks, with the right lexer names if non-Python
• PEP builds with no warnings, pre-commit checks pass and content displays as intended in the rendered HTML
• Authors/sponsor added to .github/CODEOWNERS for the PEP

Standards Track requirements

• PEP topic discussed in a suitable venue with general agreement that a PEP is appropriate
• Suggested sections included (unless not applicable)
  • Motivation
  • Rationale
  • Specification
  • Backwards Compatibility
  • Security Implications (none identified for this syntactic sugar)
  • How to Teach This
  • Reference Implementation (none yet)
  • Rejected Ideas
  • Open Issues (n/a)
• Python-Version set to valid (pre-beta) future Python version, if relevant
• Any project stated in the PEP as supporting/endorsing/benefiting from the PEP formally confirmed such
• Right before or after initial merging, PEP discussion thread created and linked to in Discussions-To and Post-History

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📚 Documentation preview 📚: https://pep-previews--4581.org.readthedocs.build/

[JelleZijlstra]

Looks good, thanks! A couple minor points left.

Are you already working on a reference implementation? I started fiddling with the grammar a bit but not sure I'll have time to fully implement the PEP.

[Zac-HD]

I'm not working on a reference implementation at the moment, but of course if you want to sponsor the PEP without implementing it that's totally fine!

[AA-Turner]

@Zac-HD please don't force push if you can avoid it.

A

[hugovk]

I've added the new PEP checklist from https://github.com/python/peps/blob/main/.github/PULL_REQUEST_TEMPLATE/Add%20a%20new%20PEP.md to the top post, please could you go through it and mark off those that apply?