bpo-44456: Improve the syntax error when mixing keyword and positional patterns #26793
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Hm, maybe we should loosen this rule to catch any time a positional pattern follows a keyword one. We also want to catch cases like |
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Grammar/python.gram
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| invalid_class_argument_pattern[asdl_pattern_seq*]: | ||
| | positional_patterns ',' keyword_patterns ',' a=positional_patterns { a } | ||
| | keyword_patterns ',' a=positional_patterns ',' keyword_patterns { a } | ||
| | keyword_patterns ',' a=positional_patterns { a } |
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Hm. Would something like this (untested) catch all invalid cases where a positional pattern follows a keyword one?
| invalid_class_argument_pattern[asdl_pattern_seq*]: | |
| | positional_patterns ',' keyword_patterns ',' a=positional_patterns { a } | |
| | keyword_patterns ',' a=positional_patterns ',' keyword_patterns { a } | |
| | keyword_patterns ',' a=positional_patterns { a } | |
| invalid_class_argument_pattern[asdl_pattern_seq*]: | |
| | [positional_patterns ','] keyword_patterns ',' a=positional_patterns (',' keyword_patterns ',' positional_patterns)* [',' keyword_patterns] { a } |
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I'm imagining an arbitrarily-long pathological case like C(a=b, c, d=e, f, g=h, i, j=k, ...), for example. Maybe it's not worth catching, but it seems like it would be easy enough to do.
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I think we can cover that if we rely on eager parsing on the rule above:
>>> match x:
... case C(a=b, c, d=e, f, g=h, i, j=k, ...):
File "<stdin>", line 2
case C(a=b, c, d=e, f, g=h, i, j=k, ...):
^
SyntaxError: positional patterns follow keyword patterns
with
diff --git a/Grammar/python.gram b/Grammar/python.gram
index df49d5de63..8f0bb70fc3 100644
--- a/Grammar/python.gram
+++ b/Grammar/python.gram
@@ -980,7 +980,7 @@ invalid_as_pattern:
| or_pattern 'as' a="_" { RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "cannot use '_' as a target") }
| or_pattern 'as' !NAME a=expression { RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "invalid pattern target") }
invalid_class_pattern:
- | name_or_attr '(' a=invalid_class_argument_pattern ','? ')' { RAISE_SYNTAX_ERROR_KNOWN_RANGE(
+ | name_or_attr '(' a=invalid_class_argument_pattern { RAISE_SYNTAX_ERROR_KNOWN_RANGE(
PyPegen_first_item(a, pattern_ty),
PyPegen_last_item(a, pattern_ty),
"positional patterns follow keyword patterns") }|
Gotcha. So then |
Yup |
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Thanks @pablogsal for the PR 🌮🎉.. I'm working now to backport this PR to: 3.10. |
…l patterns (pythonGH-26793) (cherry picked from commit 0acc258) Co-authored-by: Pablo Galindo <Pablogsal@gmail.com>
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GH-26900 is a backport of this pull request to the 3.10 branch. |
https://bugs.python.org/issue44456