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[syntax-errors] Positional-only parameters before Python 3.8 (#16481)

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Summary
--

Detect positional-only parameters before Python 3.8, as marked by the
`/` separator in a parameter list.

Test Plan
--
Inline tests.
This commit is contained in:
Brent Westbrook 2025-03-05 08:46:43 -05:00 • committed by GitHub
parent 23fd4927ae
commit d0623888b3
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5
crates/ruff_python_parser/resources/inline/err/pos_only_py37.py Normal file
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@ -0,0 +1,5 @@
# parse_options: {"target-version": "3.7"}
def foo(a, /): ...
def foo(a, /, b, /): ...
def foo(a, *args, /, b): ...
def foo(a, //): ...

2
crates/ruff_python_parser/resources/inline/ok/pos_only_py38.py Normal file
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@ -0,0 +1,2 @@
# parse_options: {"target-version": "3.8"}
def foo(a, /): ...

30
crates/ruff_python_parser/src/error.rs
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@ -449,6 +449,32 @@ pub enum UnsupportedSyntaxErrorKind {
Match, Match,
Walrus, Walrus,
ExceptStar, ExceptStar,
/// Represents the use of a [PEP 570] positional-only parameter before Python 3.8.
///
/// ## Examples
///
/// Python 3.8 added the `/` syntax for marking preceding parameters as positional-only:
///
/// ```python
/// def foo(a, b, /, c): ...
/// ```
///
/// This means `a` and `b` in this case can only be provided by position, not by name. In other
/// words, this code results in a `TypeError` at runtime:
///
/// ```pycon
/// >>> def foo(a, b, /, c): ...
/// ...
/// >>> foo(a=1, b=2, c=3)
/// Traceback (most recent call last):
/// File "<python-input-3>", line 1, in <module>
/// foo(a=1, b=2, c=3)
/// ~~~^^^^^^^^^^^^^^^
/// TypeError: foo() got some positional-only arguments passed as keyword arguments: 'a, b'
/// ```
///
/// [PEP 570]: https://peps.python.org/pep-0570/
PositionalOnlyParameter,
/// Represents the use of a [type parameter list] before Python 3.12. /// Represents the use of a [type parameter list] before Python 3.12.
/// ///
/// ## Examples /// ## Examples
@ -487,6 +513,9 @@ impl Display for UnsupportedSyntaxError {
UnsupportedSyntaxErrorKind::Match => "Cannot use `match` statement", UnsupportedSyntaxErrorKind::Match => "Cannot use `match` statement",
UnsupportedSyntaxErrorKind::Walrus => "Cannot use named assignment expression (`:=`)", UnsupportedSyntaxErrorKind::Walrus => "Cannot use named assignment expression (`:=`)",
UnsupportedSyntaxErrorKind::ExceptStar => "Cannot use `except*`", UnsupportedSyntaxErrorKind::ExceptStar => "Cannot use `except*`",
UnsupportedSyntaxErrorKind::PositionalOnlyParameter => {
"Cannot use positional-only parameter separator"
}
UnsupportedSyntaxErrorKind::TypeParameterList => "Cannot use type parameter lists", UnsupportedSyntaxErrorKind::TypeParameterList => "Cannot use type parameter lists",
UnsupportedSyntaxErrorKind::TypeAliasStatement => "Cannot use `type` alias statement", UnsupportedSyntaxErrorKind::TypeAliasStatement => "Cannot use `type` alias statement",
UnsupportedSyntaxErrorKind::TypeParamDefault => { UnsupportedSyntaxErrorKind::TypeParamDefault => {
@ -509,6 +538,7 @@ impl UnsupportedSyntaxErrorKind {
UnsupportedSyntaxErrorKind::Match => PythonVersion::PY310, UnsupportedSyntaxErrorKind::Match => PythonVersion::PY310,
UnsupportedSyntaxErrorKind::Walrus => PythonVersion::PY38, UnsupportedSyntaxErrorKind::Walrus => PythonVersion::PY38,
UnsupportedSyntaxErrorKind::ExceptStar => PythonVersion::PY311, UnsupportedSyntaxErrorKind::ExceptStar => PythonVersion::PY311,
UnsupportedSyntaxErrorKind::PositionalOnlyParameter => PythonVersion::PY38,
UnsupportedSyntaxErrorKind::TypeParameterList => PythonVersion::PY312, UnsupportedSyntaxErrorKind::TypeParameterList => PythonVersion::PY312,
UnsupportedSyntaxErrorKind::TypeAliasStatement => PythonVersion::PY312, UnsupportedSyntaxErrorKind::TypeAliasStatement => PythonVersion::PY312,
UnsupportedSyntaxErrorKind::TypeParamDefault => PythonVersion::PY313, UnsupportedSyntaxErrorKind::TypeParamDefault => PythonVersion::PY313,

15
crates/ruff_python_parser/src/parser/statement.rs
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@ -3050,6 +3050,21 @@ impl<'src> Parser<'src> {
// first time, otherwise it's a user error. // first time, otherwise it's a user error.
std::mem::swap(&mut parameters.args, &mut parameters.posonlyargs); std::mem::swap(&mut parameters.args, &mut parameters.posonlyargs);
seen_positional_only_separator = true; seen_positional_only_separator = true;
// test_ok pos_only_py38
// # parse_options: {"target-version": "3.8"}
// def foo(a, /): ...
// test_err pos_only_py37
// # parse_options: {"target-version": "3.7"}
// def foo(a, /): ...
// def foo(a, /, b, /): ...
// def foo(a, *args, /, b): ...
// def foo(a, //): ...
parser.add_unsupported_syntax_error(
UnsupportedSyntaxErrorKind::PositionalOnlyParameter,
slash_range,
);
} }
last_keyword_only_separator_range = None; last_keyword_only_separator_range = None;

291
crates/ruff_python_parser/tests/snapshots/invalid_syntax@pos_only_py37.py.snap Normal file
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@ -0,0 +1,291 @@
---
source: crates/ruff_python_parser/tests/fixtures.rs
input_file: crates/ruff_python_parser/resources/inline/err/pos_only_py37.py
---
## AST
```
Module(
ModModule {
range: 0..136,
body: [
FunctionDef(
StmtFunctionDef {
range: 43..61,
is_async: false,
decorator_list: [],
name: Identifier {
id: Name("foo"),
range: 47..50,
},
type_params: None,
parameters: Parameters {
range: 50..56,
posonlyargs: [
ParameterWithDefault {
range: 51..52,
parameter: Parameter {
range: 51..52,
name: Identifier {
id: Name("a"),
range: 51..52,
},
annotation: None,
},
default: None,
},
],
args: [],
vararg: None,
kwonlyargs: [],
kwarg: None,
},
returns: None,
body: [
Expr(
StmtExpr {
range: 58..61,
value: EllipsisLiteral(
ExprEllipsisLiteral {
range: 58..61,
},
),
},
),
],
},
),
FunctionDef(
StmtFunctionDef {
range: 62..86,
is_async: false,
decorator_list: [],
name: Identifier {
id: Name("foo"),
range: 66..69,
},
type_params: None,
parameters: Parameters {
range: 69..81,
posonlyargs: [
ParameterWithDefault {
range: 70..71,
parameter: Parameter {
range: 70..71,
name: Identifier {
id: Name("a"),
range: 70..71,
},
annotation: None,
},
default: None,
},
],
args: [
ParameterWithDefault {
range: 76..77,
parameter: Parameter {
range: 76..77,
name: Identifier {
id: Name("b"),
range: 76..77,
},
annotation: None,
},
default: None,
},
],
vararg: None,
kwonlyargs: [],
kwarg: None,
},
returns: None,
body: [
Expr(
StmtExpr {
range: 83..86,
value: EllipsisLiteral(
ExprEllipsisLiteral {
range: 83..86,
},
),
},
),
],
},
),
FunctionDef(
StmtFunctionDef {
range: 87..115,
is_async: false,
decorator_list: [],
name: Identifier {
id: Name("foo"),
range: 91..94,
},
type_params: None,
parameters: Parameters {
range: 94..110,
posonlyargs: [
ParameterWithDefault {
range: 95..96,
parameter: Parameter {
range: 95..96,
name: Identifier {
id: Name("a"),
range: 95..96,
},
annotation: None,
},
default: None,
},
],
args: [],
vararg: Some(
Parameter {
range: 98..103,
name: Identifier {
id: Name("args"),
range: 99..103,
},
annotation: None,
},
),
kwonlyargs: [
ParameterWithDefault {
range: 108..109,
parameter: Parameter {
range: 108..109,
name: Identifier {
id: Name("b"),
range: 108..109,
},
annotation: None,
},
default: None,
},
],
kwarg: None,
},
returns: None,
body: [
Expr(
StmtExpr {
range: 112..115,
value: EllipsisLiteral(
ExprEllipsisLiteral {
range: 112..115,
},
),
},
),
],
},
),
FunctionDef(
StmtFunctionDef {
range: 116..135,
is_async: false,
decorator_list: [],
name: Identifier {
id: Name("foo"),
range: 120..123,
},
type_params: None,
parameters: Parameters {
range: 123..130,
posonlyargs: [],
args: [
ParameterWithDefault {
range: 124..125,
parameter: Parameter {
range: 124..125,
name: Identifier {
id: Name("a"),
range: 124..125,
},
annotation: None,
},
default: None,
},
],
vararg: None,
kwonlyargs: [],
kwarg: None,
},
returns: None,
body: [
Expr(
StmtExpr {
range: 132..135,
value: EllipsisLiteral(
ExprEllipsisLiteral {
range: 132..135,
},
),
},
),
],
},
),
],
},
)
```
## Errors
|
1 | # parse_options: {"target-version": "3.7"}
2 | def foo(a, /): ...
3 | def foo(a, /, b, /): ...
| ^ Syntax Error: Only one '/' separator allowed
4 | def foo(a, *args, /, b): ...
5 | def foo(a, //): ...
|
|
2 | def foo(a, /): ...
3 | def foo(a, /, b, /): ...
4 | def foo(a, *args, /, b): ...
| ^ Syntax Error: '/' parameter must appear before '*' parameter
5 | def foo(a, //): ...
|
|
3 | def foo(a, /, b, /): ...
4 | def foo(a, *args, /, b): ...
5 | def foo(a, //): ...
| ^^ Syntax Error: Expected ',', found '//'
|
## Unsupported Syntax Errors
|
1 | # parse_options: {"target-version": "3.7"}
2 | def foo(a, /): ...
| ^ Syntax Error: Cannot use positional-only parameter separator on Python 3.7 (syntax was added in Python 3.8)
3 | def foo(a, /, b, /): ...
4 | def foo(a, *args, /, b): ...
|
|
1 | # parse_options: {"target-version": "3.7"}
2 | def foo(a, /): ...
3 | def foo(a, /, b, /): ...
| ^ Syntax Error: Cannot use positional-only parameter separator on Python 3.7 (syntax was added in Python 3.8)
4 | def foo(a, *args, /, b): ...
5 | def foo(a, //): ...
|
|
2 | def foo(a, /): ...
3 | def foo(a, /, b, /): ...
4 | def foo(a, *args, /, b): ...
| ^ Syntax Error: Cannot use positional-only parameter separator on Python 3.7 (syntax was added in Python 3.8)
5 | def foo(a, //): ...
|

61
crates/ruff_python_parser/tests/snapshots/valid_syntax@pos_only_py38.py.snap Normal file
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@ -0,0 +1,61 @@
---
source: crates/ruff_python_parser/tests/fixtures.rs
input_file: crates/ruff_python_parser/resources/inline/ok/pos_only_py38.py
---
## AST
```
Module(
ModModule {
range: 0..62,
body: [
FunctionDef(
StmtFunctionDef {
range: 43..61,
is_async: false,
decorator_list: [],
name: Identifier {
id: Name("foo"),
range: 47..50,
},
type_params: None,
parameters: Parameters {
range: 50..56,
posonlyargs: [
ParameterWithDefault {
range: 51..52,
parameter: Parameter {
range: 51..52,
name: Identifier {
id: Name("a"),
range: 51..52,
},
annotation: None,
},
default: None,
},
],
args: [],
vararg: None,
kwonlyargs: [],
kwarg: None,
},
returns: None,
body: [
Expr(
StmtExpr {
range: 58..61,
value: EllipsisLiteral(
ExprEllipsisLiteral {
range: 58..61,
},
),
},
),
],
},
),
],
},
)
```