Description

johnslavik

opened on Feb 26, 2026

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Feature or enhancement

Proposal:

Consider a specialized syntax error for these cases:

with item,: pass
with item as x,: pass

whereas this would be correct syntax:

with (item,): pass
with (item as x,): pass

This was taken from https://github.com/astral-sh/ruff/blob/6ff4da454c448f01eb0b71728f3941870c811bfc/crates/ruff_python_parser/resources/invalid/statements/with/unparenthesized_with_items.py. 2+ years in Ruff's parser.

I'm not sure what the better message could be. Maybe one of these:

❯ ./python.exe t.py
  File "/Users/bartosz.slawecki/Python/cpython/t.py", line 1
    with item,: pass
              ^
SyntaxError: single 'with' item has a trailing comma                 # this tells me what's wrong
SyntaxError: single 'with' item is followed by a comma               # this tells me about a violated rule
SyntaxError: this 'with' statement cannot end with a trailing comma  # this sets a rule
SyntaxError: single 'with' item cannot be followed by a comma        # this is not always true :-)

Only this specific case seems to require parentheses to pass.
For instance, I could also do:

with a, b: pass

Or maybe we could allow no parentheses at all? But that's probably much more work for an edge case, would it be worth it?

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Links to previous discussion of this feature:

No response

Linked PRs

• gh-145241: specialize SyntaxError for single trailing-comma with item #145282

Activity

1. johnslavik

   self-assigned this

   on Feb 26, 2026
2. johnslavik

   added

   type-featureA feature request or enhancementA feature request or enhancement

   interpreter-core(Objects, Python, Grammar, and Parser dirs)(Objects, Python, Grammar, and Parser dirs)

   topic-parser

   on Feb 26, 2026
3. johnslavik

   changed the title [-]Specialize `match` syntax error for unary addition in pattern[/-] [+]Specialize `match` syntax error for unparenthesized comma-delimited 'with' item[/+] on Feb 26, 2026
4. johnslavik

   removed their assignment

   on Feb 26, 2026
5. johnslavik commented on Feb 26, 2026

   

   johnslavik

   on Feb 26, 2026

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   cc @sobolevn @Eclips4 @pablogsal
6. terryjreedy

   changed the title [-]Specialize `match` syntax error for unparenthesized comma-delimited 'with' item[/-] [+]Specialize syntax error for unparenthesized comma-delimited 'with' item[/+] on Feb 26, 2026
7. terryjreedy commented on Feb 26, 2026

   

   terryjreedy

   on Feb 26, 2026

   Member

   More actions

   Verified standard message SyntaxError: invalid syntax on 3.15.0a6.
8. pablogsal

   added 2 commits that reference this issue on Feb 26, 2026

   pythongh-145241: specialize SyntaxError for single trailing-comma wit…

   3433bc5

   pythongh-145241: specialize SyntaxError for single trailing-comma wit…

   4994e57
9. johnslavik

   changed the title [-]Specialize syntax error for unparenthesized comma-delimited 'with' item[/-] [+]Specialize syntax error for trailing comma of last item in `with`[/+] on Feb 26, 2026
10. johnslavik commented on Feb 26, 2026

    

    johnslavik

    on Feb 26, 2026

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    While reviewing the PR, I've learned that this can be triggered by more than one with item as well. See #145282 (review).
11. pablogsal

    added a commit that references this issue on Feb 28, 2026

    gh-145241: specialize SyntaxError for single trailing-comma with item (…

    09e8c38
12. johnslavik commented on Feb 28, 2026

    

    johnslavik

    on Feb 28, 2026

    MemberAuthor

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    I'd command backports according to #142236 (comment). EDIT: Couldn't cleanly backport, I gave up.
13. johnslavik

    closed this as completedon Feb 28, 2026
14. brijkapadia

    added a commit that references this issue on Feb 28, 2026

    pythongh-145241: specialize SyntaxError for single trailing-comma wit…

    0d13a6e
15. ljfp

    added a commit that references this issue on Apr 25, 2026

    pythongh-145241: specialize SyntaxError for single trailing-comma wit…

    172eb81

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