Feature or enhancement

Proposal:

Consider a specialized syntax error for these cases:

withitem,:passwithitemasx,:pass

whereas this would be correct syntax:

with (item,):passwith (itemasx,):pass

This was taken fromhttps://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 wrongSyntaxError: single 'with' item is followed by a comma               # this tells me about a violated ruleSyntaxError: this 'with' statement cannot end with a trailing comma  # this sets a ruleSyntaxError: 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:

witha,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