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[syntax-errors] Improve error message and range for pre-PEP-614 decorator syntax errors #16581

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Merged
AlexWaygood merged 3 commits into from
Mar 17, 2025
Merged

[syntax-errors] Improve error message and range for pre-PEP-614 decorator syntax errors #16581

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63e2de2
Improve error message and range for pre-PEP-614 decorator syntax errors
AlexWaygood Mar 9, 2025
f08c43e
wip
AlexWaygood Mar 10, 2025
4158b95
Address Micha review and improve message for invalid call expression
AlexWaygood Mar 10, 2025
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4 changes: 4 additions & 0 deletions crates/ruff_python_parser/resources/inline/err/decorator_await_expression_py38.py
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# parse_options: { "target-version": "3.8" }
async def foo():
@await bar
def baz(): ...
3 changes: 3 additions & 0 deletions crates/ruff_python_parser/resources/inline/err/decorator_dict_literal_py38.py
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# parse_options: { "target-version": "3.8" }
@{3: 3}
def bar(): ...
3 changes: 3 additions & 0 deletions crates/ruff_python_parser/resources/inline/err/decorator_float_literal_py38.py
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# parse_options: { "target-version": "3.8" }
@3.14
def bar(): ...
4 changes: 4 additions & 0 deletions crates/ruff_python_parser/resources/inline/ok/decorator_await_expression_py39.py
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# parse_options: { "target-version": "3.9" }
async def foo():
@await bar
def baz(): ...
17 changes: 14 additions & 3 deletions crates/ruff_python_parser/src/error.rs
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Expand Up @@ -557,7 +557,9 @@ pub enum UnsupportedSyntaxErrorKind {
/// [PEP 614]: https://peps.python.org/pep-0614/
/// [`dotted_name`]: https://docs.python.org/3.8/reference/compound_stmts.html#grammar-token-dotted-name
/// [decorator grammar]: https://docs.python.org/3/reference/compound_stmts.html#grammar-token-python-grammar-decorator
RelaxedDecorator,
RelaxedDecorator {
invalid_node_name: &'static str,
},

/// Represents the use of a [PEP 570] positional-only parameter before Python 3.8.
///
Expand Down Expand Up @@ -633,7 +635,14 @@ impl Display for UnsupportedSyntaxError {
UnsupportedSyntaxErrorKind::StarTuple(StarTupleKind::Yield) => {
"Cannot use iterable unpacking in yield expressions"
}
UnsupportedSyntaxErrorKind::RelaxedDecorator => "Unsupported expression in decorators",
UnsupportedSyntaxErrorKind::RelaxedDecorator { invalid_node_name } => {
return write!(
f,
"Cannot use {invalid_node_name} outside function-call arguments in a decorator \
on Python {target_version} (syntax was added in Python 3.9)",
target_version = self.target_version,
);
}
UnsupportedSyntaxErrorKind::PositionalOnlyParameter => {
"Cannot use positional-only parameter separator"
}
Expand Down Expand Up @@ -677,7 +686,9 @@ impl UnsupportedSyntaxErrorKind {
UnsupportedSyntaxErrorKind::Walrus => Change::Added(PythonVersion::PY38),
UnsupportedSyntaxErrorKind::ExceptStar => Change::Added(PythonVersion::PY311),
UnsupportedSyntaxErrorKind::StarTuple(_) => Change::Added(PythonVersion::PY38),
UnsupportedSyntaxErrorKind::RelaxedDecorator => Change::Added(PythonVersion::PY39),
UnsupportedSyntaxErrorKind::RelaxedDecorator { .. } => {
Change::Added(PythonVersion::PY39)
}
UnsupportedSyntaxErrorKind::PositionalOnlyParameter => {
Change::Added(PythonVersion::PY38)
}
Expand Down
56 changes: 49 additions & 7 deletions crates/ruff_python_parser/src/parser/helpers.rs
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@@ -1,4 +1,5 @@
use ruff_python_ast::{self as ast, CmpOp, Expr, ExprContext};
use ruff_python_ast::{self as ast, CmpOp, Expr, ExprContext, Number};
use ruff_text_size::{Ranged, TextRange};

use crate::TokenKind;

Expand Down Expand Up @@ -47,11 +48,52 @@ pub(super) const fn token_kind_to_cmp_op(tokens: [TokenKind; 2]) -> Option<CmpOp
/// Helper for `parse_decorators` to determine if `expr` is a [`dotted_name`] from the decorator
/// grammar before Python 3.9.
///
/// Returns `None` if `expr` is a `dotted_name`. Returns `Some((description, range))` if it is not,
/// where `description` is a string describing the invalid node and `range` is the node's range.
///
/// [`dotted_name`]: https://docs.python.org/3.8/reference/compound_stmts.html#grammar-token-dotted-name
pub(super) fn is_name_or_attribute_expression(expr: &Expr) -> bool {
match expr {
Expr::Attribute(attr) => is_name_or_attribute_expression(&attr.value),
Expr::Name(_) => true,
_ => false,
}
pub(super) fn invalid_pre_py39_decorator_node(expr: &Expr) -> Option<(&'static str, TextRange)> {
let description = match expr {
Expr::Attribute(attr) => return invalid_pre_py39_decorator_node(&attr.value),

Expr::Name(_) => None,

Expr::NumberLiteral(number) => match &number.value {
Number::Int(_) => Some("an int literal"),
Number::Float(_) => Some("a float literal"),
Number::Complex { .. } => Some("a complex literal"),
},

Expr::BoolOp(_) => Some("boolean expression"),
Expr::BinOp(_) => Some("binary-operation expression"),
Expr::UnaryOp(_) => Some("unary-operation expression"),
Expr::Await(_) => Some("`await` expression"),
Expr::Lambda(_) => Some("lambda expression"),
Expr::If(_) => Some("conditional expression"),
Expr::Dict(_) => Some("a dict literal"),
Expr::Set(_) => Some("a set literal"),
Expr::List(_) => Some("a list literal"),
Expr::Tuple(_) => Some("a tuple literal"),
Expr::Starred(_) => Some("starred expression"),
Expr::Slice(_) => Some("slice expression"),
Expr::BytesLiteral(_) => Some("bytes literal"),
Expr::StringLiteral(_) => Some("string literal"),
Expr::EllipsisLiteral(_) => Some("ellipsis literal"),
Expr::NoneLiteral(_) => Some("`None` literal"),
Expr::BooleanLiteral(_) => Some("boolean literal"),
Expr::ListComp(_) => Some("list comprehension"),
Expr::SetComp(_) => Some("set comprehension"),
Expr::DictComp(_) => Some("dict comprehension"),
Expr::Generator(_) => Some("generator expression"),
Expr::Yield(_) => Some("`yield` expression"),
Expr::YieldFrom(_) => Some("`yield from` expression"),
Expr::Compare(_) => Some("comparison expression"),
Expr::Call(_) => Some("function call"),
Expr::FString(_) => Some("f-string"),
Expr::Named(_) => Some("assignment expression"),
Expr::Subscript(_) => Some("subscript expression"),
Expr::IpyEscapeCommand(_) => Some("IPython escape command"),
};

description.map(|description| (description, expr.range()))
}
37 changes: 31 additions & 6 deletions crates/ruff_python_parser/src/parser/statement.rs
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Expand Up @@ -2678,17 +2678,42 @@ impl<'src> Parser<'src> {
// # parse_options: { "target-version": "3.7" }
// @(x := lambda x: x)(foo)
// def bar(): ...
let allowed_decorator = match &parsed_expr.expr {

// test_err decorator_dict_literal_py38
// # parse_options: { "target-version": "3.8" }
// @{3: 3}
// def bar(): ...

// test_err decorator_float_literal_py38
// # parse_options: { "target-version": "3.8" }
// @3.14
// def bar(): ...

// test_ok decorator_await_expression_py39
// # parse_options: { "target-version": "3.9" }
// async def foo():
// @await bar
// def baz(): ...

// test_err decorator_await_expression_py38
// # parse_options: { "target-version": "3.8" }
// async def foo():
// @await bar
// def baz(): ...

let disallowed_expression = match &parsed_expr.expr {
Expr::Call(expr_call) => {
helpers::is_name_or_attribute_expression(&expr_call.func)
helpers::invalid_pre_py39_decorator_node(&expr_call.func)
}
expr => helpers::is_name_or_attribute_expression(expr),
expr => helpers::invalid_pre_py39_decorator_node(expr),
};

if !allowed_decorator {
if let Some((description, range)) = disallowed_expression {
self.add_unsupported_syntax_error(
UnsupportedSyntaxErrorKind::RelaxedDecorator,
parsed_expr.range(),
UnsupportedSyntaxErrorKind::RelaxedDecorator {
invalid_node_name: description,
},
range,
);
}
}
Expand Down
96 changes: 96 additions & 0 deletions ...ruff_python_parser/tests/snapshots/invalid_syntax@decorator_await_expression_py38.py.snap
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---
source: crates/ruff_python_parser/tests/fixtures.rs
input_file: crates/ruff_python_parser/resources/inline/err/decorator_await_expression_py38.py
---
## AST

```
Module(
ModModule {
range: 0..96,
body: [
FunctionDef(
StmtFunctionDef {
range: 45..95,
is_async: true,
decorator_list: [],
name: Identifier {
id: Name("foo"),
range: 55..58,
},
type_params: None,
parameters: Parameters {
range: 58..60,
posonlyargs: [],
args: [],
vararg: None,
kwonlyargs: [],
kwarg: None,
},
returns: None,
body: [
FunctionDef(
StmtFunctionDef {
range: 66..95,
is_async: false,
decorator_list: [
Decorator {
range: 66..76,
expression: Await(
ExprAwait {
range: 67..76,
value: Name(
ExprName {
range: 73..76,
id: Name("bar"),
ctx: Load,
},
),
},
),
},
],
name: Identifier {
id: Name("baz"),
range: 85..88,
},
type_params: None,
parameters: Parameters {
range: 88..90,
posonlyargs: [],
args: [],
vararg: None,
kwonlyargs: [],
kwarg: None,
},
returns: None,
body: [
Expr(
StmtExpr {
range: 92..95,
value: EllipsisLiteral(
ExprEllipsisLiteral {
range: 92..95,
},
),
},
),
],
},
),
],
},
),
],
},
)
```
## Unsupported Syntax Errors

|
1 | # parse_options: { "target-version": "3.8" }
2 | async def foo():
3 | @await bar
| ^^^^^^^^^ Syntax Error: Cannot use `await` expression outside function-call arguments in a decorator on Python 3.8 (syntax was added in Python 3.9)
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@dhruvmanila dhruvmanila Mar 10, 2025 •
edited
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I actually find the "outside function-call arguments in a decorator" part a bit confusing because it made me think that this is only allowed in function-call arguments. I'd possibly remove it and keep it simply "Cannot use await expression in a decorator on Python 3.8 ..." but then the message cannot be used in a general way because, in this example, the await expression is only not allowed at the top-level (@(await x)) while @decorator(await x) would be ok.

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@AlexWaygood AlexWaygood Mar 10, 2025

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Oh, I see. So you interpreted "outside function-call arguments" as meaning "If I add parentheses, it will be valid syntax"?

Hmm, I'm not sure how to clarify that :/ adding the parentheses doesn't make it a function call -- but I can see how a beginner might find the language confusing. Would you find "outside call expression arguments" any clearer?

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@dhruvmanila dhruvmanila Mar 17, 2025

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Sorry for the late reply, what I thought it could be interpreted is related to the function that's being decorated and not the decorator itself. But, I think what you've is fine as well. We can iterate if anyone finds it confusing.

4 | def baz(): ...
|
87 changes: 87 additions & 0 deletions crates/ruff_python_parser/tests/snapshots/invalid_syntax@decorator_dict_literal_py38.py.snap
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---
source: crates/ruff_python_parser/tests/fixtures.rs
input_file: crates/ruff_python_parser/resources/inline/err/decorator_dict_literal_py38.py
---
## AST

```
Module(
ModModule {
range: 0..68,
body: [
FunctionDef(
StmtFunctionDef {
range: 45..67,
is_async: false,
decorator_list: [
Decorator {
range: 45..52,
expression: Dict(
ExprDict {
range: 46..52,
items: [
DictItem {
key: Some(
NumberLiteral(
ExprNumberLiteral {
range: 47..48,
value: Int(
3,
),
},
),
),
value: NumberLiteral(
ExprNumberLiteral {
range: 50..51,
value: Int(
3,
),
},
),
},
],
},
),
},
],
name: Identifier {
id: Name("bar"),
range: 57..60,
},
type_params: None,
parameters: Parameters {
range: 60..62,
posonlyargs: [],
args: [],
vararg: None,
kwonlyargs: [],
kwarg: None,
},
returns: None,
body: [
Expr(
StmtExpr {
range: 64..67,
value: EllipsisLiteral(
ExprEllipsisLiteral {
range: 64..67,
},
),
},
),
],
},
),
],
},
)
```
## Unsupported Syntax Errors

|
1 | # parse_options: { "target-version": "3.8" }
2 | @{3: 3}
| ^^^^^^ Syntax Error: Cannot use a dict literal outside function-call arguments in a decorator on Python 3.8 (syntax was added in Python 3.9)
3 | def bar(): ...
|
2 changes: 1 addition & 1 deletion crates/ruff_python_parser/tests/snapshots/invalid_syntax@decorator_expression_py38.py.snap
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Expand Up @@ -96,6 +96,6 @@ Module(
|
1 | # parse_options: { "target-version": "3.8" }
2 | @buttons[0].clicked.connect
| ^^^^^^^^^^^^^^^^^^^^^^^^^^ Syntax Error: Unsupported expression in decorators on Python 3.8 (syntax was added in Python 3.9)
| ^^^^^^^^^^ Syntax Error: Cannot use subscript expression outside function-call arguments in a decorator on Python 3.8 (syntax was added in Python 3.9)
3 | def spam(): ...
|
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