[flake8-commas] Stabilize support for trailing comma checks in type parameter lists (COM812, COM819) (#20275)

Introduced in #19390. Removed gating, updated tests. No documentation to
update.

Author: dylwil3

crates/ruff_linter/src/preview.rs

@@ -222,11 +222,6 @@ pub(crate) const fn is_add_future_annotations_imports_enabled(settings: &LinterS
     settings.preview.is_enabled()
 }
 
-// https://github.com/astral-sh/ruff/pull/19390
-pub(crate) const fn is_trailing_comma_type_params_enabled(settings: &LinterSettings) -> bool {
-    settings.preview.is_enabled()
-}
-
 // https://github.com/astral-sh/ruff/pull/19851
 pub(crate) const fn is_maxsplit_without_separator_fix_enabled(settings: &LinterSettings) -> bool {
     settings.preview.is_enabled()

crates/ruff_linter/src/rules/flake8_commas/mod.rs

@@ -10,7 +10,7 @@ mod tests {
 
     use crate::registry::Rule;
     use crate::test::test_path;
-    use crate::{assert_diagnostics, assert_diagnostics_diff, settings};
+    use crate::{assert_diagnostics, settings};
 
     #[test_case(Path::new("COM81.py"))]
     #[test_case(Path::new("COM81_syntax_error.py"))]
@@ -27,28 +27,4 @@ mod tests {
         assert_diagnostics!(snapshot, diagnostics);
         Ok(())
     }
-
-    #[test_case(Path::new("COM81.py"))]
-    #[test_case(Path::new("COM81_syntax_error.py"))]
-    fn preview_rules(path: &Path) -> Result<()> {
-        let snapshot = format!("preview_diff__{}", path.to_string_lossy());
-        let rules = vec![
-            Rule::MissingTrailingComma,
-            Rule::TrailingCommaOnBareTuple,
-            Rule::ProhibitedTrailingComma,
-        ];
-        let settings_before = settings::LinterSettings::for_rules(rules.clone());
-        let settings_after = settings::LinterSettings {
-            preview: crate::settings::types::PreviewMode::Enabled,
-            ..settings::LinterSettings::for_rules(rules)
-        };
-
-        assert_diagnostics_diff!(
-            snapshot,
-            Path::new("flake8_commas").join(path).as_path(),
-            &settings_before,
-            &settings_after
-        );
-        Ok(())
-    }
 }

crates/ruff_linter/src/rules/flake8_commas/rules/trailing_commas.rs

@@ -5,8 +5,6 @@ use ruff_text_size::{Ranged, TextRange};
 
 use crate::Locator;
 use crate::checkers::ast::LintContext;
-use crate::preview::is_trailing_comma_type_params_enabled;
-use crate::settings::LinterSettings;
 use crate::{AlwaysFixableViolation, Violation};
 use crate::{Edit, Fix};
 
@@ -298,7 +296,7 @@ pub(crate) fn trailing_commas(
         }
 
         // Update the comma context stack.
-        let context = update_context(token, prev, prev_prev, &mut stack, lint_context.settings());
+        let context = update_context(token, prev, prev_prev, &mut stack);
 
         check_token(token, prev, prev_prev, context, locator, lint_context);
 
@@ -417,7 +415,6 @@ fn update_context(
     prev: SimpleToken,
     prev_prev: SimpleToken,
     stack: &mut Vec<Context>,
-    settings: &LinterSettings,
 ) -> Context {
     let new_context = match token.ty {
         TokenType::OpeningBracket => match (prev.ty, prev_prev.ty) {
@@ -427,19 +424,11 @@ fn update_context(
             }
             _ => Context::new(ContextType::Tuple),
         },
-        TokenType::OpeningSquareBracket if is_trailing_comma_type_params_enabled(settings) => {
-            match (prev.ty, prev_prev.ty) {
-                (TokenType::Named, TokenType::Def | TokenType::Class | TokenType::Type) => {
-                    Context::new(ContextType::TypeParameters)
-                }
-                (TokenType::ClosingBracket | TokenType::Named | TokenType::String, _) => {
-                    Context::new(ContextType::Subscript)
-                }
-                _ => Context::new(ContextType::List),
+        TokenType::OpeningSquareBracket => match (prev.ty, prev_prev.ty) {
+            (TokenType::Named, TokenType::Def | TokenType::Class | TokenType::Type) => {
+                Context::new(ContextType::TypeParameters)
             }
-        }
-        TokenType::OpeningSquareBracket => match prev.ty {
-            TokenType::ClosingBracket | TokenType::Named | TokenType::String => {
+            (TokenType::ClosingBracket | TokenType::Named | TokenType::String, _) => {
                 Context::new(ContextType::Subscript)
             }
             _ => Context::new(ContextType::List),

crates/ruff_linter/src/rules/flake8_commas/snapshots/ruff_linter__rules__flake8_commas__tests__COM81.py.snap

@@ -939,3 +939,111 @@ help: Add trailing comma
 644 | )
 645 | 
 646 | assert False, f"<- This is not a trailing comma"
+
+COM812 [*] Trailing comma missing
+   --> COM81.py:655:6
+    |
+654 | type X[
+655 |     T
+    |      ^
+656 | ] = T
+657 | def f[
+    |
+help: Add trailing comma
+652 | }"""
+653 | 
+654 | type X[
+    -     T
+655 +     T,
+656 | ] = T
+657 | def f[
+658 |     T
+
+COM812 [*] Trailing comma missing
+   --> COM81.py:658:6
+    |
+656 | ] = T
+657 | def f[
+658 |     T
+    |      ^
+659 | ](): pass
+660 | class C[
+    |
+help: Add trailing comma
+655 |     T
+656 | ] = T
+657 | def f[
+    -     T
+658 +     T,
+659 | ](): pass
+660 | class C[
+661 |     T
+
+COM812 [*] Trailing comma missing
+   --> COM81.py:661:6
+    |
+659 | ](): pass
+660 | class C[
+661 |     T
+    |      ^
+662 | ]: pass
+    |
+help: Add trailing comma
+658 |     T
+659 | ](): pass
+660 | class C[
+    -     T
+661 +     T,
+662 | ]: pass
+663 | 
+664 | type X[T,] = T
+
+COM819 [*] Trailing comma prohibited
+   --> COM81.py:664:9
+    |
+662 | ]: pass
+663 |
+664 | type X[T,] = T
+    |         ^
+665 | def f[T,](): pass
+666 | class C[T,]: pass
+    |
+help: Remove trailing comma
+661 |     T
+662 | ]: pass
+663 | 
+    - type X[T,] = T
+664 + type X[T] = T
+665 | def f[T,](): pass
+666 | class C[T,]: pass
+
+COM819 [*] Trailing comma prohibited
+   --> COM81.py:665:8
+    |
+664 | type X[T,] = T
+665 | def f[T,](): pass
+    |        ^
+666 | class C[T,]: pass
+    |
+help: Remove trailing comma
+662 | ]: pass
+663 | 
+664 | type X[T,] = T
+    - def f[T,](): pass
+665 + def f[T](): pass
+666 | class C[T,]: pass
+
+COM819 [*] Trailing comma prohibited
+   --> COM81.py:666:10
+    |
+664 | type X[T,] = T
+665 | def f[T,](): pass
+666 | class C[T,]: pass
+    |          ^
+    |
+help: Remove trailing comma
+663 | 
+664 | type X[T,] = T
+665 | def f[T,](): pass
+    - class C[T,]: pass
+666 + class C[T]: pass