From c0fb235a703684bca1cc1767015bb7e19ab1c22f Mon Sep 17 00:00:00 2001
From: Dan Parizher <105245560+danparizher@users.noreply.github.com>
Date: Fri, 19 Sep 2025 09:27:14 -0400
Subject: [PATCH] [`flake8-comprehensions`] Preserve trailing commas for
 single-element lists (`C409`) (#19571)

## Summary

Fixes #19568
---
 .../fixtures/flake8_comprehensions/C409.py    |  3 ++
 .../unnecessary_literal_within_tuple_call.rs  |  2 +-
 ...8_comprehensions__tests__C409_C409.py.snap | 33 +++++++++++++++++++
 ...ensions__tests__preview__C409_C409.py.snap | 33 +++++++++++++++++++
 4 files changed, 70 insertions(+), 1 deletion(-)

diff --git a/crates/ruff_linter/resources/test/fixtures/flake8_comprehensions/C409.py b/crates/ruff_linter/resources/test/fixtures/flake8_comprehensions/C409.py
index c2c093b253..b8c72773d6 100644
--- a/crates/ruff_linter/resources/test/fixtures/flake8_comprehensions/C409.py
+++ b/crates/ruff_linter/resources/test/fixtures/flake8_comprehensions/C409.py
@@ -42,3 +42,6 @@ tuple(
         x for x in [1,2,3]
     }
 )
+
+t9 = tuple([1],)
+t10 = tuple([1, 2],)
diff --git a/crates/ruff_linter/src/rules/flake8_comprehensions/rules/unnecessary_literal_within_tuple_call.rs b/crates/ruff_linter/src/rules/flake8_comprehensions/rules/unnecessary_literal_within_tuple_call.rs
index b2d3af263f..30a250e7ce 100644
--- a/crates/ruff_linter/src/rules/flake8_comprehensions/rules/unnecessary_literal_within_tuple_call.rs
+++ b/crates/ruff_linter/src/rules/flake8_comprehensions/rules/unnecessary_literal_within_tuple_call.rs
@@ -124,7 +124,7 @@ pub(crate) fn unnecessary_literal_within_tuple_call(
                 let needs_trailing_comma = if let [item] = elts.as_slice() {
                     SimpleTokenizer::new(
                         checker.locator().contents(),
-                        TextRange::new(item.end(), call.end()),
+                        TextRange::new(item.end(), argument.end()),
                     )
                     .all(|token| token.kind != SimpleTokenKind::Comma)
                 } else {
diff --git a/crates/ruff_linter/src/rules/flake8_comprehensions/snapshots/ruff_linter__rules__flake8_comprehensions__tests__C409_C409.py.snap b/crates/ruff_linter/src/rules/flake8_comprehensions/snapshots/ruff_linter__rules__flake8_comprehensions__tests__C409_C409.py.snap
index f05149dffd..f8c7534525 100644
--- a/crates/ruff_linter/src/rules/flake8_comprehensions/snapshots/ruff_linter__rules__flake8_comprehensions__tests__C409_C409.py.snap
+++ b/crates/ruff_linter/src/rules/flake8_comprehensions/snapshots/ruff_linter__rules__flake8_comprehensions__tests__C409_C409.py.snap
@@ -247,3 +247,36 @@ help: Rewrite as a tuple literal
 28 | tuple([x for x in range(5)])
 29 | tuple({x for x in range(10)})
 note: This is an unsafe fix and may change runtime behavior
+
+C409 [*] Unnecessary list literal passed to `tuple()` (rewrite as a tuple literal)
+  --> C409.py:46:6
+   |
+44 | )
+45 |
+46 | t9 = tuple([1],)
+   |      ^^^^^^^^^^^
+47 | t10 = tuple([1, 2],)
+   |
+help: Rewrite as a tuple literal
+43 |     }
+44 | )
+45 | 
+   - t9 = tuple([1],)
+46 + t9 = (1,)
+47 | t10 = tuple([1, 2],)
+note: This is an unsafe fix and may change runtime behavior
+
+C409 [*] Unnecessary list literal passed to `tuple()` (rewrite as a tuple literal)
+  --> C409.py:47:7
+   |
+46 | t9 = tuple([1],)
+47 | t10 = tuple([1, 2],)
+   |       ^^^^^^^^^^^^^^
+   |
+help: Rewrite as a tuple literal
+44 | )
+45 | 
+46 | t9 = tuple([1],)
+   - t10 = tuple([1, 2],)
+47 + t10 = (1, 2)
+note: This is an unsafe fix and may change runtime behavior
diff --git a/crates/ruff_linter/src/rules/flake8_comprehensions/snapshots/ruff_linter__rules__flake8_comprehensions__tests__preview__C409_C409.py.snap b/crates/ruff_linter/src/rules/flake8_comprehensions/snapshots/ruff_linter__rules__flake8_comprehensions__tests__preview__C409_C409.py.snap
index fbf5aa8fcd..23657a1310 100644
--- a/crates/ruff_linter/src/rules/flake8_comprehensions/snapshots/ruff_linter__rules__flake8_comprehensions__tests__preview__C409_C409.py.snap
+++ b/crates/ruff_linter/src/rules/flake8_comprehensions/snapshots/ruff_linter__rules__flake8_comprehensions__tests__preview__C409_C409.py.snap
@@ -344,3 +344,36 @@ help: Rewrite as a generator
 42 |         x for x in [1,2,3]
 43 |     }
 note: This is an unsafe fix and may change runtime behavior
+
+C409 [*] Unnecessary list literal passed to `tuple()` (rewrite as a tuple literal)
+  --> C409.py:46:6
+   |
+44 | )
+45 |
+46 | t9 = tuple([1],)
+   |      ^^^^^^^^^^^
+47 | t10 = tuple([1, 2],)
+   |
+help: Rewrite as a tuple literal
+43 |     }
+44 | )
+45 | 
+   - t9 = tuple([1],)
+46 + t9 = (1,)
+47 | t10 = tuple([1, 2],)
+note: This is an unsafe fix and may change runtime behavior
+
+C409 [*] Unnecessary list literal passed to `tuple()` (rewrite as a tuple literal)
+  --> C409.py:47:7
+   |
+46 | t9 = tuple([1],)
+47 | t10 = tuple([1, 2],)
+   |       ^^^^^^^^^^^^^^
+   |
+help: Rewrite as a tuple literal
+44 | )
+45 | 
+46 | t9 = tuple([1],)
+   - t10 = tuple([1, 2],)
+47 + t10 = (1, 2)
+note: This is an unsafe fix and may change runtime behavior