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bpo-43017: Improve error message for unparenthesised tuples in comprehensions #24314

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Merged
pablogsal merged 3 commits into from
Jan 31, 2021
Merged

bpo-43017: Improve error message for unparenthesised tuples in comprehensions #24314

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8c84ffc
bpo-43017: Improve error message for unparenthesised tuples in compre…
pablogsal Jan 24, 2021
e11786b
Update Grammar/python.gram
pablogsal Jan 26, 2021
b3aefe7
fixup! Update Grammar/python.gram
pablogsal Jan 28, 2021
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8 changes: 5 additions & 3 deletions Grammar/python.gram
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Original file line number Diff line number Diff line change
Expand Up @@ -507,7 +507,7 @@ strings[expr_ty] (memo): a=STRING+ { _PyPegen_concatenate_strings(p, a) }
list[expr_ty]:
| '[' a=[star_named_expressions] ']' { _Py_List(a, Load, EXTRA) }
listcomp[expr_ty]:
| '[' a=named_expression ~ b=for_if_clauses ']' { _Py_ListComp(a, b, EXTRA) }
| '[' a=named_expression b=for_if_clauses ']' { _Py_ListComp(a, b, EXTRA) }
| invalid_comprehension
tuple[expr_ty]:
| '(' a=[y=star_named_expression ',' z=[star_named_expressions] { _PyPegen_seq_insert_in_front(p, y, z) } ] ')' {
Expand All @@ -516,11 +516,11 @@ group[expr_ty]:
| '(' a=(yield_expr | named_expression) ')' { a }
| invalid_group
genexp[expr_ty]:
| '(' a=named_expression ~ b=for_if_clauses ')' { _Py_GeneratorExp(a, b, EXTRA) }
| '(' a=named_expression b=for_if_clauses ')' { _Py_GeneratorExp(a, b, EXTRA) }
| invalid_comprehension
set[expr_ty]: '{' a=star_named_expressions '}' { _Py_Set(a, EXTRA) }
setcomp[expr_ty]:
| '{' a=named_expression ~ b=for_if_clauses '}' { _Py_SetComp(a, b, EXTRA) }
| '{' a=named_expression b=for_if_clauses '}' { _Py_SetComp(a, b, EXTRA) }
| invalid_comprehension
dict[expr_ty]:
| '{' a=[double_starred_kvpairs] '}' {
Expand Down Expand Up @@ -692,6 +692,8 @@ invalid_primary:
invalid_comprehension:
| ('[' | '(' | '{') a=starred_expression for_if_clauses {
RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "iterable unpacking cannot be used in comprehension") }
| ('[' | '{') a=star_named_expression ',' [star_named_expressions] {
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RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "did you forget parentheses around the comprehension target?") }
invalid_dict_comprehension:
| '{' a='**' bitwise_or for_if_clauses '}' {
RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "dict unpacking cannot be used in dict comprehension") }
Expand Down
3 changes: 2 additions & 1 deletion Lib/test/test_named_expressions.py
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Expand Up @@ -101,7 +101,8 @@ def test_named_expression_invalid_16(self):
def test_named_expression_invalid_17(self):
code = "[i := 0, j := 1 for i, j in [(1, 2), (3, 4)]]"

with self.assertRaisesRegex(SyntaxError, "invalid syntax"):
with self.assertRaisesRegex(SyntaxError,
"did you forget parentheses around the comprehension target?"):
exec(code, {}, {})

def test_named_expression_invalid_in_class_body(self):
Expand Down
15 changes: 15 additions & 0 deletions Lib/test/test_syntax.py
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Expand Up @@ -235,6 +235,21 @@
Traceback (most recent call last):
SyntaxError: invalid syntax

Comprehensions creating tuples without parentheses
should produce a specialized error message:

>>> [x,y for x,y in range(100)]
Traceback (most recent call last):
SyntaxError: did you forget parentheses around the comprehension target?

>>> {x,y for x,y in range(100)}
Traceback (most recent call last):
SyntaxError: did you forget parentheses around the comprehension target?

>>> {x,y: None for x,y in range(100)}
Traceback (most recent call last):
SyntaxError: did you forget parentheses around the comprehension target?

From compiler_complex_args():

>>> def f(None=1):
Expand Down
2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Core and Builtins/2021-01-24-18-02-05.bpo-43017.emEcXX.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Improve error message in the parser when using un-parenthesised tuples in
comprehensions. Patch by Pablo Galindo.
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