PEP 785: New methods for easier handling of ExceptionGroups

[Zac-HD]

I've discussed this fairly extensively with @gpshead, and we've been using related functions at work for some time now. I'm therefore posting the PR now to get the process rolling; I also expect to polish the prose (especially the footnotes) a little further before merging.

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
  (apologies for the intitial confusion here)
• 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)
  • How to Teach This
  • Reference Implementation
  • Rejected Ideas
  • Open Issues
    (none identified)
• 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--4357.org.readthedocs.build/

[JelleZijlstra]

Why not use the next available number (785)?

[Zac-HD]

Why not use the next available number (785)?

Because I've also got PEP-789, and I was worried about getting them mixed up in conversation 😅

[JelleZijlstra]

Overall looks good, left some feedback inline.

[AA-Turner]

Why not use the next available number (785)?

Because I've also got PEP-789, and I was worried about getting them mixed up in conversation 😅

From PEP 1:

NNNN should be the next available PEP number not used by a published or in-PR PEP.

I don't have strong feelings, but I think we should encourage authors to keep PEP numbers in order, we've had recent confusion with gaps etc in the assigned numbers (777, 789).

A

[hugovk]

I don't have strong feelings, but I think we should encourage authors to keep PEP numbers in order, we've had recent confusion with gaps etc in the assigned numbers (777, 789).

I agree, we don't want authors jumping to the next tens if they already have a PEP in the current one, it'll be tricky to defrag (and we don't want to run out of integers 🙃).

[AA-Turner]

Initial brief review:

[AA-Turner]

I don't have strong feelings, but I think we should encourage authors to keep PEP numbers in order, we've had recent confusion with gaps etc in the assigned numbers (777, 789).

I agree, we don't want authors jumping to the next tens if they already have a PEP in the current one, it'll be tricky to defrag (and we don't want to run out of integers 🙃).

This has again caused confusion, see #4365, where the author chose PEP 791 as the 'next' number.

@Zac-HD please could you renumber this PEP to 785, and then we can assign #4365 as PEP 786 (assuming it gets a sponsor)?

A

[Zac-HD]

Thank you all for the reviews - I've fixed the PEP number, and also implemented the suggestions from first-pass review. (even deleting the second space after each period!)

Looking at the build failure, I don't think that's me - it hasn't even read that far yet:

reading sources... [ 28%] pep-0343 .. pep-0383

Sphinx parallel build error:
AttributeError: 'Values' object has no attribute 'env'
make: *** [Makefile:24: html] Error 2
reading sources... [ 33%] pep-0384 .. pep-0425

[hugovk]

Ready to merge?

[Zac-HD]

Did a final self-review and fixed some formatting and minor expression issues; I'm now ready to merge. Thanks again to everyone above!

[hugovk]

Hmm, GitHub says all comments must be resolved, but as far as I can see, they all are?

we believe all comments were addressed and github just isn't gettin' it.

[gpshead]

I used Claude Code to find the comments on the PR that GitHub refused to expose in its UI and make Github GraphQL API calls to mark them as resolved.

there were two stranded review comments unresolved from hugo 5 days ago that the force push'es had garbage collected from git so the github UI wouldn't allow you to see them from the files changes -> conversations view other than linking to broken links to them.

[gpshead]

(if you're a claude user, ask it to use the gh command line and to use the github GraphQL API and it'll start figuring out the magic...)

[hugovk]

@Zac-HD Please could you open a quick PR to add the discussion thread to Discussions-To and Post-History? Thank you!