[flake8-pyi]: More autofixes for redundant-none-literal (PYI061) (#14872)

Co-authored-by: Alex Waygood <alex.waygood@gmail.com>

crates/ruff_linter/src/rules/flake8_pyi/rules/redundant_none_literal.rs

@@ -1,15 +1,14 @@
 use ruff_diagnostics::{Applicability, Diagnostic, Edit, Fix, FixAvailability, Violation};
 use ruff_macros::{derive_message_formats, ViolationMetadata};
-use ruff_python_ast::{Expr, ExprBinOp, ExprNoneLiteral, ExprSubscript, Operator};
+use ruff_python_ast::{
-use ruff_python_semantic::{
+    self as ast, Expr, ExprBinOp, ExprContext, ExprNoneLiteral, ExprSubscript, Operator,
-    analyze::typing::{traverse_literal, traverse_union},
-    SemanticModel,
 };
-use ruff_text_size::Ranged;
+use ruff_python_semantic::analyze::typing::{traverse_literal, traverse_union};
+use ruff_text_size::{Ranged, TextRange};
 
 use smallvec::SmallVec;
 
-use crate::checkers::ast::Checker;
+use crate::{checkers::ast::Checker, settings::types::PythonVersion};
 
 /// ## What it does
 /// Checks for redundant `Literal[None]` annotations.
@@ -34,9 +33,14 @@ use crate::checkers::ast::Checker;
 /// Literal[1, 2, 3, "foo", 5] | None
 /// ```
 ///
-/// ## Fix safety
+/// ## Fix safety and availability
 /// This rule's fix is marked as safe unless the literal contains comments.
 ///
+/// There is currently no fix available if there are other elements in the `Literal` slice aside
+/// from `None` and [`target-version`] is set to Python 3.9 or lower, as the fix always uses the
+/// `|` syntax to create unions rather than `typing.Union`, and the `|` syntax for unions was added
+/// in Python 3.10.
+///
 /// ## References
 /// - [Typing documentation: Legal parameters for `Literal` at type check time](https://typing.readthedocs.io/en/latest/spec/literal.html#legal-parameters-for-literal-at-type-check-time)
 #[derive(ViolationMetadata)]
@@ -65,35 +69,44 @@ impl Violation for RedundantNoneLiteral {
     }
 }
 
-/// RUF037
+/// PYI061
 pub(crate) fn redundant_none_literal<'a>(checker: &mut Checker, literal_expr: &'a Expr) {
-    if !checker.semantic().seen_typing() {
+    let semantic = checker.semantic();
+
+    if !semantic.seen_typing() {
         return;
     }
 
-    let mut none_exprs: SmallVec<[&ExprNoneLiteral; 1]> = SmallVec::new();
+    let Expr::Subscript(ast::ExprSubscript {
-    let mut other_literal_elements_seen = false;
+        value: literal_subscript,
+        ..
+    }) = literal_expr
+    else {
+        return;
+    };
 
-    let mut find_none = |expr: &'a Expr, _parent: &'a Expr| {
+    let mut none_exprs: SmallVec<[&ExprNoneLiteral; 1]> = SmallVec::new();
+    let mut literal_elements = vec![];
+
+    let mut partition_literal_elements = |expr: &'a Expr, _parent: &'a Expr| {
         if let Expr::NoneLiteral(none_expr) = expr {
             none_exprs.push(none_expr);
         } else {
-            other_literal_elements_seen = true;
+            literal_elements.push(expr);
         }
     };
 
-    traverse_literal(&mut find_none, checker.semantic(), literal_expr);
+    traverse_literal(&mut partition_literal_elements, semantic, literal_expr);
 
     if none_exprs.is_empty() {
         return;
     }
 
-    // Provide a [`Fix`] when the complete `Literal` can be replaced. Applying the fix
+    let other_literal_elements_seen = !literal_elements.is_empty();
-    // can leave an unused import to be fixed by the `unused-import` rule.
+
-    let fix = if other_literal_elements_seen {
+    // N.B. Applying the fix can leave an unused import to be fixed by the `unused-import` rule.
-        None
+    let fix =
-    } else {
+        create_fix_edit(checker, literal_expr, literal_subscript, literal_elements).map(|edit| {
-        create_fix_edit(checker.semantic(), literal_expr).map(|edit| {
             Fix::applicable_edit(
                 edit,
                 if checker.comment_ranges().intersects(literal_expr.range()) {
@@ -102,8 +115,7 @@ pub(crate) fn redundant_none_literal<'a>(checker: &mut Checker, literal_expr: &'
                     Applicability::Safe
                 },
             )
-        })
+        });
-    };
 
     for none_expr in none_exprs {
         let mut diagnostic = Diagnostic::new(
@@ -128,7 +140,14 @@ pub(crate) fn redundant_none_literal<'a>(checker: &mut Checker, literal_expr: &'
 /// See <https://github.com/astral-sh/ruff/issues/14567>.
 ///
 /// [`typing.Union`]: https://docs.python.org/3/library/typing.html#typing.Union
-fn create_fix_edit(semantic: &SemanticModel, literal_expr: &Expr) -> Option<Edit> {
+fn create_fix_edit(
+    checker: &Checker,
+    literal_expr: &Expr,
+    literal_subscript: &Expr,
+    literal_elements: Vec<&Expr>,
+) -> Option<Edit> {
+    let semantic = checker.semantic();
+
     let enclosing_pep604_union = semantic
         .current_expressions()
         .skip(1)
@@ -143,8 +162,9 @@ fn create_fix_edit(semantic: &SemanticModel, literal_expr: &Expr) -> Option<Edit
         })
         .last();
 
-    let mut is_fixable = true;
     if let Some(enclosing_pep604_union) = enclosing_pep604_union {
+        let mut is_fixable = true;
+
         traverse_union(
             &mut |expr, _| {
                 if matches!(expr, Expr::NoneLiteral(_)) {
@@ -163,7 +183,46 @@ fn create_fix_edit(semantic: &SemanticModel, literal_expr: &Expr) -> Option<Edit
             semantic,
             enclosing_pep604_union,
         );
+
+        if !is_fixable {
+            return None;
+        }
     }
 
-    is_fixable.then(|| Edit::range_replacement("None".to_string(), literal_expr.range()))
+    if literal_elements.is_empty() {
+        return Some(Edit::range_replacement(
+            "None".to_string(),
+            literal_expr.range(),
+        ));
+    }
+
+    if checker.settings.target_version < PythonVersion::Py310 {
+        return None;
+    }
+
+    let bin_or = Expr::BinOp(ExprBinOp {
+        range: TextRange::default(),
+        left: Box::new(Expr::Subscript(ast::ExprSubscript {
+            value: Box::new(literal_subscript.clone()),
+            range: TextRange::default(),
+            ctx: ExprContext::Load,
+            slice: Box::new(if literal_elements.len() > 1 {
+                Expr::Tuple(ast::ExprTuple {
+                    elts: literal_elements.into_iter().cloned().collect(),
+                    range: TextRange::default(),
+                    ctx: ExprContext::Load,
+                    parenthesized: true,
+                })
+            } else {
+                literal_elements[0].clone()
+            }),
+        })),
+        op: ruff_python_ast::Operator::BitOr,
+        right: Box::new(Expr::NoneLiteral(ExprNoneLiteral {
+            range: TextRange::default(),
+        })),
+    });
+
+    let content = checker.generator().expr(&bin_or);
+    Some(Edit::range_replacement(content, literal_expr.range()))
 }

crates/ruff_linter/src/rules/flake8_pyi/snapshots/ruff_linter__rules__flake8_pyi__tests__PYI061_PYI061.py.snap

@@ -1,5 +1,6 @@
 ---
 source: crates/ruff_linter/src/rules/flake8_pyi/mod.rs
+snapshot_kind: text
 ---
 PYI061.py:4:25: PYI061 [*] `Literal[None]` can be replaced with `None`
   |
@@ -55,7 +56,7 @@ PYI061.py:12:24: PYI061 [*] `Literal[None]` can be replaced with `None`
 14 14 | 
 15 15 | 
 
-PYI061.py:16:30: PYI061 `Literal[None, ...]` can be replaced with `Literal[...] | None`
+PYI061.py:16:30: PYI061 [*] `Literal[None, ...]` can be replaced with `Literal[...] | None`
    |
 16 | def func4(arg1: Literal[int, None, float]):
    |                              ^^^^ PYI061
@@ -63,6 +64,16 @@ PYI061.py:16:30: PYI061 `Literal[None, ...]` can be replaced with `Literal[...]
    |
    = help: Replace with `Literal[...] | None`
 
+ℹ Safe fix
+13 13 |     ...
+14 14 | 
+15 15 | 
+16    |-def func4(arg1: Literal[int, None, float]):
+   16 |+def func4(arg1: Literal[int, float] | None):
+17 17 |     ...
+18 18 | 
+19 19 | 
+
 PYI061.py:20:25: PYI061 [*] `Literal[None]` can be replaced with `None`
    |
 20 | def func5(arg1: Literal[None, None]):
@@ -99,7 +110,7 @@ PYI061.py:20:31: PYI061 [*] `Literal[None]` can be replaced with `None`
 22 22 | 
 23 23 | 
 
-PYI061.py:26:5: PYI061 `Literal[None, ...]` can be replaced with `Literal[...] | None`
+PYI061.py:26:5: PYI061 [*] `Literal[None, ...]` can be replaced with `Literal[...] | None`
    |
 24 | def func6(arg1: Literal[
 25 |     "hello",
@@ -110,6 +121,20 @@ PYI061.py:26:5: PYI061 `Literal[None, ...]` can be replaced with `Literal[...] |
    |
    = help: Replace with `Literal[...] | None`
 
+ℹ Unsafe fix
+21 21 |     ...
+22 22 | 
+23 23 | 
+24    |-def func6(arg1: Literal[
+25    |-    "hello",
+26    |-    None  # Comment 1
+27    |-    , "world"
+28    |-    ]):
+   24 |+def func6(arg1: Literal["hello", "world"] | None):
+29 25 |     ...
+30 26 | 
+31 27 | 
+
 PYI061.py:33:5: PYI061 [*] `Literal[None]` can be replaced with `None`
    |
 32 | def func7(arg1: Literal[
@@ -177,7 +202,7 @@ PYI061.py:52:9: PYI061 [*] `Literal[None]` can be replaced with `None`
 54 54 | 
 55 55 | ###
 
-PYI061.py:53:15: PYI061 `Literal[None, ...]` can be replaced with `Literal[...] | None`
+PYI061.py:53:15: PYI061 [*] `Literal[None, ...]` can be replaced with `Literal[...] | None`
    |
 51 | # From flake8-pyi
 52 | Literal[None]  # Y061 None inside "Literal[]" expression. Replace with "None"
@@ -188,6 +213,16 @@ PYI061.py:53:15: PYI061 `Literal[None, ...]` can be replaced with `Literal[...]
    |
    = help: Replace with `Literal[...] | None`
 
+ℹ Safe fix
+50 50 | 
+51 51 | # From flake8-pyi
+52 52 | Literal[None]  # Y061 None inside "Literal[]" expression. Replace with "None"
+53    |-Literal[True, None]  # Y061 None inside "Literal[]" expression. Replace with "Literal[True] | None"
+   53 |+Literal[True] | None  # Y061 None inside "Literal[]" expression. Replace with "Literal[True] | None"
+54 54 | 
+55 55 | ###
+56 56 | # The following rules here are slightly subtle,
+
 PYI061.py:62:9: PYI061 [*] `Literal[None]` can be replaced with `None`
    |
 60 | # If Y061 and Y062 both apply, but all the duplicate members are None,
@@ -228,7 +263,7 @@ PYI061.py:62:15: PYI061 [*] `Literal[None]` can be replaced with `None`
 64 64 | 
 65 65 | # ... but if Y061 and Y062 both apply
 
-PYI061.py:63:12: PYI061 `Literal[None, ...]` can be replaced with `Literal[...] | None`
+PYI061.py:63:12: PYI061 [*] `Literal[None, ...]` can be replaced with `Literal[...] | None`
    |
 61 | # only emit Y061...
 62 | Literal[None, None]  # Y061 None inside "Literal[]" expression. Replace with "None"
@@ -239,7 +274,17 @@ PYI061.py:63:12: PYI061 `Literal[None, ...]` can be replaced with `Literal[...]
    |
    = help: Replace with `Literal[...] | None`
 
-PYI061.py:63:25: PYI061 `Literal[None, ...]` can be replaced with `Literal[...] | None`
+ℹ Safe fix
+60 60 | # If Y061 and Y062 both apply, but all the duplicate members are None,
+61 61 | # only emit Y061...
+62 62 | Literal[None, None]  # Y061 None inside "Literal[]" expression. Replace with "None"
+63    |-Literal[1, None, "foo", None]  # Y061 None inside "Literal[]" expression. Replace with "Literal[1, 'foo'] | None"
+   63 |+Literal[1, "foo"] | None  # Y061 None inside "Literal[]" expression. Replace with "Literal[1, 'foo'] | None"
+64 64 | 
+65 65 | # ... but if Y061 and Y062 both apply
+66 66 | # and there are no None members in the Literal[] slice,
+
+PYI061.py:63:25: PYI061 [*] `Literal[None, ...]` can be replaced with `Literal[...] | None`
    |
 61 | # only emit Y061...
 62 | Literal[None, None]  # Y061 None inside "Literal[]" expression. Replace with "None"
@@ -250,7 +295,17 @@ PYI061.py:63:25: PYI061 `Literal[None, ...]` can be replaced with `Literal[...]
    |
    = help: Replace with `Literal[...] | None`
 
-PYI061.py:68:9: PYI061 `Literal[None, ...]` can be replaced with `Literal[...] | None`
+ℹ Safe fix
+60 60 | # If Y061 and Y062 both apply, but all the duplicate members are None,
+61 61 | # only emit Y061...
+62 62 | Literal[None, None]  # Y061 None inside "Literal[]" expression. Replace with "None"
+63    |-Literal[1, None, "foo", None]  # Y061 None inside "Literal[]" expression. Replace with "Literal[1, 'foo'] | None"
+   63 |+Literal[1, "foo"] | None  # Y061 None inside "Literal[]" expression. Replace with "Literal[1, 'foo'] | None"
+64 64 | 
+65 65 | # ... but if Y061 and Y062 both apply
+66 66 | # and there are no None members in the Literal[] slice,
+
+PYI061.py:68:9: PYI061 [*] `Literal[None, ...]` can be replaced with `Literal[...] | None`
    |
 66 | # and there are no None members in the Literal[] slice,
 67 | # only emit Y062:
@@ -259,7 +314,17 @@ PYI061.py:68:9: PYI061 `Literal[None, ...]` can be replaced with `Literal[...] |
    |
    = help: Replace with `Literal[...] | None`
 
-PYI061.py:68:21: PYI061 `Literal[None, ...]` can be replaced with `Literal[...] | None`
+ℹ Safe fix
+65 65 | # ... but if Y061 and Y062 both apply
+66 66 | # and there are no None members in the Literal[] slice,
+67 67 | # only emit Y062:
+68    |-Literal[None, True, None, True]  # Y062 Duplicate "Literal[]" member "True"
+   68 |+Literal[True, True] | None  # Y062 Duplicate "Literal[]" member "True"
+69 69 | 
+70 70 | 
+71 71 | # Regression tests for https://github.com/astral-sh/ruff/issues/14567
+
+PYI061.py:68:21: PYI061 [*] `Literal[None, ...]` can be replaced with `Literal[...] | None`
    |
 66 | # and there are no None members in the Literal[] slice,
 67 | # only emit Y062:
@@ -268,6 +333,16 @@ PYI061.py:68:21: PYI061 `Literal[None, ...]` can be replaced with `Literal[...]
    |
    = help: Replace with `Literal[...] | None`
 
+ℹ Safe fix
+65 65 | # ... but if Y061 and Y062 both apply
+66 66 | # and there are no None members in the Literal[] slice,
+67 67 | # only emit Y062:
+68    |-Literal[None, True, None, True]  # Y062 Duplicate "Literal[]" member "True"
+   68 |+Literal[True, True] | None  # Y062 Duplicate "Literal[]" member "True"
+69 69 | 
+70 70 | 
+71 71 | # Regression tests for https://github.com/astral-sh/ruff/issues/14567
+
 PYI061.py:72:12: PYI061 `Literal[None]` can be replaced with `None`
    |
 71 | # Regression tests for https://github.com/astral-sh/ruff/issues/14567

crates/ruff_linter/src/rules/flake8_pyi/snapshots/ruff_linter__rules__flake8_pyi__tests__PYI061_PYI061.pyi.snap

@@ -1,5 +1,6 @@
 ---
 source: crates/ruff_linter/src/rules/flake8_pyi/mod.rs
+snapshot_kind: text
 ---
 PYI061.pyi:4:25: PYI061 [*] `Literal[None]` can be replaced with `None`
   |
@@ -52,13 +53,23 @@ PYI061.pyi:10:24: PYI061 [*] `Literal[None]` can be replaced with `None`
 12 12 | 
 13 13 | def func4(arg1: Literal[int, None, float]): ...
 
-PYI061.pyi:13:30: PYI061 `Literal[None, ...]` can be replaced with `Literal[...] | None`
+PYI061.pyi:13:30: PYI061 [*] `Literal[None, ...]` can be replaced with `Literal[...] | None`
    |
 13 | def func4(arg1: Literal[int, None, float]): ...
    |                              ^^^^ PYI061
    |
    = help: Replace with `Literal[...] | None`
 
+ℹ Safe fix
+10 10 | def func3() -> Literal[None]: ...
+11 11 | 
+12 12 | 
+13    |-def func4(arg1: Literal[int, None, float]): ...
+   13 |+def func4(arg1: Literal[int, float] | None): ...
+14 14 | 
+15 15 | 
+16 16 | def func5(arg1: Literal[None, None]): ...
+
 PYI061.pyi:16:25: PYI061 [*] `Literal[None]` can be replaced with `None`
    |
 16 | def func5(arg1: Literal[None, None]): ...
@@ -93,7 +104,7 @@ PYI061.pyi:16:31: PYI061 [*] `Literal[None]` can be replaced with `None`
 18 18 | 
 19 19 | def func6(arg1: Literal[
 
-PYI061.pyi:21:5: PYI061 `Literal[None, ...]` can be replaced with `Literal[...] | None`
+PYI061.pyi:21:5: PYI061 [*] `Literal[None, ...]` can be replaced with `Literal[...] | None`
    |
 19 | def func6(arg1: Literal[
 20 |     "hello",
@@ -104,6 +115,20 @@ PYI061.pyi:21:5: PYI061 `Literal[None, ...]` can be replaced with `Literal[...]
    |
    = help: Replace with `Literal[...] | None`
 
+ℹ Unsafe fix
+16 16 | def func5(arg1: Literal[None, None]): ...
+17 17 | 
+18 18 | 
+19    |-def func6(arg1: Literal[
+20    |-    "hello",
+21    |-    None  # Comment 1
+22    |-    , "world"
+23    |-]): ...
+   19 |+def func6(arg1: Literal["hello", "world"] | None): ...
+24 20 | 
+25 21 | 
+26 22 | def func7(arg1: Literal[
+
 PYI061.pyi:27:5: PYI061 [*] `Literal[None]` can be replaced with `None`
    |
 26 | def func7(arg1: Literal[
@@ -168,7 +193,7 @@ PYI061.pyi:42:9: PYI061 [*] `Literal[None]` can be replaced with `None`
 44 44 | 
 45 45 | 
 
-PYI061.pyi:43:15: PYI061 `Literal[None, ...]` can be replaced with `Literal[...] | None`
+PYI061.pyi:43:15: PYI061 [*] `Literal[None, ...]` can be replaced with `Literal[...] | None`
    |
 41 | # From flake8-pyi
 42 | Literal[None]  # PYI061 None inside "Literal[]" expression. Replace with "None"
@@ -177,6 +202,16 @@ PYI061.pyi:43:15: PYI061 `Literal[None, ...]` can be replaced with `Literal[...]
    |
    = help: Replace with `Literal[...] | None`
 
+ℹ Safe fix
+40 40 | 
+41 41 | # From flake8-pyi
+42 42 | Literal[None]  # PYI061 None inside "Literal[]" expression. Replace with "None"
+43    |-Literal[True, None]  # PYI061 None inside "Literal[]" expression. Replace with "Literal[True] | None"
+   43 |+Literal[True] | None  # PYI061 None inside "Literal[]" expression. Replace with "Literal[True] | None"
+44 44 | 
+45 45 | 
+46 46 | # Regression tests for https://github.com/astral-sh/ruff/issues/14567
+
 PYI061.pyi:47:12: PYI061 `Literal[None]` can be replaced with `None`
    |
 46 | # Regression tests for https://github.com/astral-sh/ruff/issues/14567