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gh-129545 Improve Syntax Error Message for Default Parameter Order #130937

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gh-129545 Improve Syntax Error Message for Default Parameter Order #130937

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a751060
Update python.gram
sharktide Mar 6, 2025
f996904
Update test_positional_only_arg.py
sharktide Mar 6, 2025
74ea7f6
gh-129545 Enhance error messages
sharktide Mar 7, 2025
a5c8ef5
Merge branch 'python:main' into patch-129545
sharktide Mar 7, 2025
db494fb
Update test_positional_only_arg.py
sharktide Mar 7, 2025
38b5230
Merge branch 'python:main' into patch-129545
sharktide Mar 7, 2025
6468fe8
📜🤖 Added by blurb_it.
blurb-it[bot] Mar 7, 2025
8d436d9
Update Misc/NEWS.d/next/C_API/2025-03-07-16-48-12.gh-issue-129545.t-9…
sharktide Mar 7, 2025
467ce0c
@lysnikolaou moved news entry to Core_and_Builtins
sharktide Mar 7, 2025
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4 changes: 2 additions & 2 deletions Grammar/python.gram
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Original file line number Diff line number Diff line change
Expand Up @@ -1259,7 +1259,7 @@ invalid_parameters:
| (slash_no_default | slash_with_default) param_maybe_default* a='/' {
RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "/ may appear only once") }
| slash_no_default? param_no_default* invalid_parameters_helper a=param_no_default {
RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "parameter without a default follows parameter with a default") }
RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "positional parameter without a default follows parameter with a default") }
| param_no_default* a='(' param_no_default+ ','? b=')' {
RAISE_SYNTAX_ERROR_KNOWN_RANGE(a, b, "Function parameters cannot be parenthesized") }
| (slash_no_default | slash_with_default)? param_maybe_default* '*' (',' | param_no_default) param_maybe_default* a='/' {
Expand Down Expand Up @@ -1287,7 +1287,7 @@ invalid_lambda_parameters:
| (lambda_slash_no_default | lambda_slash_with_default) lambda_param_maybe_default* a='/' {
RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "/ may appear only once") }
| lambda_slash_no_default? lambda_param_no_default* invalid_lambda_parameters_helper a=lambda_param_no_default {
RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "parameter without a default follows parameter with a default") }
RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "positional parameter without a default follows parameter with a default") }
| lambda_param_no_default* a='(' ','.lambda_param+ ','? b=')' {
RAISE_SYNTAX_ERROR_KNOWN_RANGE(a, b, "Lambda expression parameters cannot be parenthesized") }
| (lambda_slash_no_default | lambda_slash_with_default)? lambda_param_maybe_default* '*' (',' | lambda_param_no_default) lambda_param_maybe_default* a='/' {
Expand Down
30 changes: 15 additions & 15 deletions Lib/test/test_positional_only_arg.py
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Original file line number Diff line number Diff line change
Expand Up @@ -24,11 +24,11 @@ def assertRaisesSyntaxError(self, codestr, regex="invalid syntax"):
compile(codestr + "\n", "<test>", "single")

def test_invalid_syntax_errors(self):
check_syntax_error(self, "def f(a, b = 5, /, c): pass", "parameter without a default follows parameter with a default")
check_syntax_error(self, "def f(a = 5, b, /, c): pass", "parameter without a default follows parameter with a default")
check_syntax_error(self, "def f(a = 5, b=1, /, c, *, d=2): pass", "parameter without a default follows parameter with a default")
check_syntax_error(self, "def f(a = 5, b, /): pass", "parameter without a default follows parameter with a default")
check_syntax_error(self, "def f(a, /, b = 5, c): pass", "parameter without a default follows parameter with a default")
check_syntax_error(self, "def f(a, b = 5, /, c): pass", "positional parameter without a default follows parameter with a default")
check_syntax_error(self, "def f(a = 5, b, /, c): pass", "positional parameter without a default follows parameter with a default")
check_syntax_error(self, "def f(a = 5, b=1, /, c, *, d=2): pass", "positional parameter without a default follows parameter with a default")
check_syntax_error(self, "def f(a = 5, b, /): pass", "positional parameter without a default follows parameter with a default")
check_syntax_error(self, "def f(a, /, b = 5, c): pass", "positional parameter without a default follows parameter with a default")
check_syntax_error(self, "def f(*args, /): pass")
check_syntax_error(self, "def f(*args, a, /): pass")
check_syntax_error(self, "def f(**kwargs, /): pass")
Expand All @@ -46,11 +46,11 @@ def test_invalid_syntax_errors(self):
check_syntax_error(self, "def f(a, *, c, /, d, e): pass")

def test_invalid_syntax_errors_async(self):
check_syntax_error(self, "async def f(a, b = 5, /, c): pass", "parameter without a default follows parameter with a default")
check_syntax_error(self, "async def f(a = 5, b, /, c): pass", "parameter without a default follows parameter with a default")
check_syntax_error(self, "async def f(a = 5, b=1, /, c, d=2): pass", "parameter without a default follows parameter with a default")
check_syntax_error(self, "async def f(a = 5, b, /): pass", "parameter without a default follows parameter with a default")
check_syntax_error(self, "async def f(a, /, b = 5, c): pass", "parameter without a default follows parameter with a default")
check_syntax_error(self, "async def f(a, b = 5, /, c): pass", "positional parameter without a default follows parameter with a default")
check_syntax_error(self, "async def f(a = 5, b, /, c): pass", "positional parameter without a default follows parameter with a default")
check_syntax_error(self, "async def f(a = 5, b=1, /, c, d=2): pass", "positional parameter without a default follows parameter with a default")
check_syntax_error(self, "async def f(a = 5, b, /): pass", "positional parameter without a default follows parameter with a default")
check_syntax_error(self, "async def f(a, /, b = 5, c): pass", "positional parameter without a default follows parameter with a default")
check_syntax_error(self, "async def f(*args, /): pass")
check_syntax_error(self, "async def f(*args, a, /): pass")
check_syntax_error(self, "async def f(**kwargs, /): pass")
Expand Down Expand Up @@ -234,11 +234,11 @@ def test_lambdas(self):
self.assertEqual(x(1, 2), 3)

def test_invalid_syntax_lambda(self):
check_syntax_error(self, "lambda a, b = 5, /, c: None", "parameter without a default follows parameter with a default")
check_syntax_error(self, "lambda a = 5, b, /, c: None", "parameter without a default follows parameter with a default")
check_syntax_error(self, "lambda a = 5, b=1, /, c, *, d=2: None", "parameter without a default follows parameter with a default")
check_syntax_error(self, "lambda a = 5, b, /: None", "parameter without a default follows parameter with a default")
check_syntax_error(self, "lambda a, /, b = 5, c: None", "parameter without a default follows parameter with a default")
check_syntax_error(self, "lambda a, b = 5, /, c: None", "positional parameter without a default follows parameter with a default")
check_syntax_error(self, "lambda a = 5, b, /, c: None", "positional parameter without a default follows parameter with a default")
check_syntax_error(self, "lambda a = 5, b=1, /, c, *, d=2: None", "positional parameter without a default follows parameter with a default")
check_syntax_error(self, "lambda a = 5, b, /: None", "positional parameter without a default follows parameter with a default")
check_syntax_error(self, "lambda a, /, b = 5, c: None", "positional parameter without a default follows parameter with a default")
check_syntax_error(self, "lambda *args, /: None")
check_syntax_error(self, "lambda *args, a, /: None")
check_syntax_error(self, "lambda **kwargs, /: None")
Expand Down
8 changes: 4 additions & 4 deletions Lib/test/test_syntax.py
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Original file line number Diff line number Diff line change
Expand Up @@ -394,12 +394,12 @@
>>> def f(x, y=1, z):
... pass
Traceback (most recent call last):
SyntaxError: parameter without a default follows parameter with a default
SyntaxError: positional parameter without a default follows parameter with a default
>>> def f(x, /, y=1, z):
... pass
Traceback (most recent call last):
SyntaxError: parameter without a default follows parameter with a default
SyntaxError: positional parameter without a default follows parameter with a default
>>> def f(x, None):
... pass
Expand Down Expand Up @@ -622,11 +622,11 @@
>>> lambda a,d=3,c: None
Traceback (most recent call last):
SyntaxError: parameter without a default follows parameter with a default
SyntaxError: positional parameter without a default follows parameter with a default
>>> lambda a,/,d=3,c: None
Traceback (most recent call last):
SyntaxError: parameter without a default follows parameter with a default
SyntaxError: positional parameter without a default follows parameter with a default
>>> import ast; ast.parse('''
... def f(
Expand Down
3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Core_and_Builtins/2025-03-07-16-48-12.gh-issue-129545.t-9iTH.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
Change the text of the ``SyntaxError: parameter without a default follows parameter with a default``
to ``SyntaxError: positional parameter without a default follows parameter with a default`` to improve
error message clarity in certain cases.
4 changes: 2 additions & 2 deletions Parser/parser.c
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