[pyupgrade] - add PEP646 Unpack conversion to * with fix (UP044) (#13988)

Co-authored-by: Micha Reiser <micha@reiser.io>

crates/ruff_linter/resources/test/fixtures/pyupgrade/UP044.py

@@ -0,0 +1,19 @@
+from typing import Generic, TypeVarTuple, Unpack
+
+Shape = TypeVarTuple('Shape')
+
+class C(Generic[Unpack[Shape]]):
+    pass
+
+class D(Generic[Unpack  [Shape]]):
+    pass
+
+def f(*args: Unpack[tuple[int, ...]]): pass
+
+def f(*args: Unpack[other.Type]): pass
+
+
+# Not valid unpackings but they are valid syntax
+def foo(*args: Unpack[int | str]) -> None: pass
+def foo(*args: Unpack[int and str]) -> None: pass
+def foo(*args: Unpack[int > str]) -> None: pass

crates/ruff_linter/src/checkers/ast/analyze/expression.rs

@@ -150,6 +150,10 @@ pub(crate) fn expression(expr: &Expr, checker: &mut Checker) {
                 ruff::rules::subscript_with_parenthesized_tuple(checker, subscript);
             }
 
+            if checker.enabled(Rule::NonPEP646Unpack) {
+                pyupgrade::rules::use_pep646_unpack(checker, subscript);
+            }
+
             pandas_vet::rules::subscript(checker, value, expr);
         }
         Expr::Tuple(ast::ExprTuple {

crates/ruff_linter/src/codes.rs

@@ -528,6 +528,7 @@ pub fn code_to_rule(linter: Linter, code: &str) -> Option<(RuleGroup, Rule)> {
         (Pyupgrade, "041") => (RuleGroup::Stable, rules::pyupgrade::rules::TimeoutErrorAlias),
         (Pyupgrade, "042") => (RuleGroup::Preview, rules::pyupgrade::rules::ReplaceStrEnum),
         (Pyupgrade, "043") => (RuleGroup::Preview, rules::pyupgrade::rules::UnnecessaryDefaultTypeArgs),
+        (Pyupgrade, "044") => (RuleGroup::Preview, rules::pyupgrade::rules::NonPEP646Unpack),
 
         // pydocstyle
         (Pydocstyle, "100") => (RuleGroup::Stable, rules::pydocstyle::rules::UndocumentedPublicModule),

crates/ruff_linter/src/rules/pyupgrade/mod.rs

@@ -235,4 +235,18 @@ mod tests {
         assert_messages!(diagnostics);
         Ok(())
     }
+
+    #[test]
+    fn unpack_pep_646_py311() -> Result<()> {
+        let diagnostics = test_path(
+            Path::new("pyupgrade/UP044.py"),
+            &settings::LinterSettings {
+                preview: PreviewMode::Enabled,
+                target_version: PythonVersion::Py311,
+                ..settings::LinterSettings::for_rule(Rule::NonPEP646Unpack)
+            },
+        )?;
+        assert_messages!(diagnostics);
+        Ok(())
+    }
 }

crates/ruff_linter/src/rules/pyupgrade/rules/mod.rs

@@ -35,6 +35,7 @@ pub(crate) use unpacked_list_comprehension::*;
 pub(crate) use use_pep585_annotation::*;
 pub(crate) use use_pep604_annotation::*;
 pub(crate) use use_pep604_isinstance::*;
+pub(crate) use use_pep646_unpack::*;
 pub(crate) use use_pep695_type_alias::*;
 pub(crate) use useless_metaclass_type::*;
 pub(crate) use useless_object_inheritance::*;
@@ -77,6 +78,7 @@ mod unpacked_list_comprehension;
 mod use_pep585_annotation;
 mod use_pep604_annotation;
 mod use_pep604_isinstance;
+mod use_pep646_unpack;
 mod use_pep695_type_alias;
 mod useless_metaclass_type;
 mod useless_object_inheritance;

crates/ruff_linter/src/rules/pyupgrade/rules/use_pep646_unpack.rs

@@ -0,0 +1,87 @@
+use ruff_diagnostics::{Diagnostic, Edit, Fix, FixAvailability, Violation};
+use ruff_macros::{derive_message_formats, violation};
+use ruff_python_ast::ExprSubscript;
+
+use crate::{checkers::ast::Checker, settings::types::PythonVersion};
+
+/// ## What it does
+/// Checks for uses of `Unpack[]` on Python 3.11 and above, and suggests
+/// using `*` instead.
+///
+/// ## Why is this bad?
+/// [PEP 646] introduced a new syntax for unpacking sequences based on the `*`
+/// operator. This syntax is more concise and readable than the previous
+/// `typing.Unpack` syntax.
+///
+/// ## Example
+///
+/// ```python
+/// from typing import Unpack
+///
+///
+/// def foo(*args: Unpack[tuple[int, ...]]) -> None:
+///     pass
+/// ```
+///
+/// Use instead:
+///
+/// ```python
+/// def foo(*args: *tuple[int, ...]) -> None:
+///     pass
+/// ```
+///
+/// ## References
+/// - [PEP 646](https://peps.python.org/pep-0646/#unpack-for-backwards-compatibility)
+#[violation]
+pub struct NonPEP646Unpack;
+
+impl Violation for NonPEP646Unpack {
+    const FIX_AVAILABILITY: FixAvailability = FixAvailability::Always;
+
+    #[derive_message_formats]
+    fn message(&self) -> String {
+        format!("Use `*` for unpacking")
+    }
+
+    fn fix_title(&self) -> Option<String> {
+        Some("Convert to `*` for unpacking".to_string())
+    }
+}
+
+/// UP044
+pub(crate) fn use_pep646_unpack(checker: &mut Checker, expr: &ExprSubscript) {
+    if checker.settings.target_version < PythonVersion::Py311 {
+        return;
+    }
+
+    if !checker.semantic().seen_typing() {
+        return;
+    }
+
+    let ExprSubscript {
+        range,
+        value,
+        slice,
+        ..
+    } = expr;
+
+    if !checker.semantic().match_typing_expr(value, "Unpack") {
+        return;
+    }
+
+    // Skip semantically invalid subscript calls (e.g. `Unpack[str | num]`).
+    if !(slice.is_name_expr() || slice.is_subscript_expr() || slice.is_attribute_expr()) {
+        return;
+    }
+
+    let mut diagnostic = Diagnostic::new(NonPEP646Unpack, *range);
+
+    let inner = checker.locator().slice(slice.as_ref());
+
+    diagnostic.set_fix(Fix::safe_edit(Edit::range_replacement(
+        format!("*{inner}"),
+        *range,
+    )));
+
+    checker.diagnostics.push(diagnostic);
+}

crates/ruff_linter/src/rules/pyupgrade/snapshots/ruff_linter__rules__pyupgrade__tests__unpack_pep_646_py311.snap

@@ -0,0 +1,83 @@
+---
+source: crates/ruff_linter/src/rules/pyupgrade/mod.rs
+snapshot_kind: text
+---
+UP044.py:5:17: UP044 [*] Use `*` for unpacking
+  |
+3 | Shape = TypeVarTuple('Shape')
+4 | 
+5 | class C(Generic[Unpack[Shape]]):
+  |                 ^^^^^^^^^^^^^ UP044
+6 |     pass
+  |
+  = help: Convert to `*` for unpacking
+
+ℹ Safe fix
+2 2 | 
+3 3 | Shape = TypeVarTuple('Shape')
+4 4 | 
+5   |-class C(Generic[Unpack[Shape]]):
+  5 |+class C(Generic[*Shape]):
+6 6 |     pass
+7 7 | 
+8 8 | class D(Generic[Unpack  [Shape]]):
+
+UP044.py:8:17: UP044 [*] Use `*` for unpacking
+  |
+6 |     pass
+7 | 
+8 | class D(Generic[Unpack  [Shape]]):
+  |                 ^^^^^^^^^^^^^^^ UP044
+9 |     pass
+  |
+  = help: Convert to `*` for unpacking
+
+ℹ Safe fix
+5 5 | class C(Generic[Unpack[Shape]]):
+6 6 |     pass
+7 7 | 
+8   |-class D(Generic[Unpack  [Shape]]):
+  8 |+class D(Generic[*Shape]):
+9 9 |     pass
+10 10 | 
+11 11 | def f(*args: Unpack[tuple[int, ...]]): pass
+
+UP044.py:11:14: UP044 [*] Use `*` for unpacking
+   |
+ 9 |     pass
+10 | 
+11 | def f(*args: Unpack[tuple[int, ...]]): pass
+   |              ^^^^^^^^^^^^^^^^^^^^^^^ UP044
+12 | 
+13 | def f(*args: Unpack[other.Type]): pass
+   |
+   = help: Convert to `*` for unpacking
+
+ℹ Safe fix
+8  8  | class D(Generic[Unpack  [Shape]]):
+9  9  |     pass
+10 10 | 
+11    |-def f(*args: Unpack[tuple[int, ...]]): pass
+   11 |+def f(*args: *tuple[int, ...]): pass
+12 12 | 
+13 13 | def f(*args: Unpack[other.Type]): pass
+14 14 | 
+
+UP044.py:13:14: UP044 [*] Use `*` for unpacking
+   |
+11 | def f(*args: Unpack[tuple[int, ...]]): pass
+12 | 
+13 | def f(*args: Unpack[other.Type]): pass
+   |              ^^^^^^^^^^^^^^^^^^ UP044
+   |
+   = help: Convert to `*` for unpacking
+
+ℹ Safe fix
+10 10 | 
+11 11 | def f(*args: Unpack[tuple[int, ...]]): pass
+12 12 | 
+13    |-def f(*args: Unpack[other.Type]): pass
+   13 |+def f(*args: *other.Type): pass
+14 14 | 
+15 15 | 
+16 16 | # Not valid unpackings but they are valid syntax

ruff.schema.json

@@ -4066,6 +4066,7 @@
         "UP041",
         "UP042",
         "UP043",
+        "UP044",
         "W",
         "W1",
         "W19",