From 12440ede9c667aa0e8cfe2aaa9e2e8f649250a0f Mon Sep 17 00:00:00 2001
From: Charlie Marsh <charlie.r.marsh@gmail.com>
Date: Fri, 13 Jan 2023 12:56:42 -0500
Subject: [PATCH] Remove non-magic trailing comma from tuple (#1854)

Closes #1821.
---
 .../fixtures/flake8_comprehensions/C405.py    |  1 +
 src/flake8_comprehensions/fixes.rs            | 24 ++++++++++++++++---
 ...8_comprehensions__tests__C405_C405.py.snap | 19 ++++++++++++++-
 3 files changed, 40 insertions(+), 4 deletions(-)

diff --git a/resources/test/fixtures/flake8_comprehensions/C405.py b/resources/test/fixtures/flake8_comprehensions/C405.py
index 8456d427de..e5f05511d1 100644
--- a/resources/test/fixtures/flake8_comprehensions/C405.py
+++ b/resources/test/fixtures/flake8_comprehensions/C405.py
@@ -3,3 +3,4 @@ s2 = set((1, 2))
 s3 = set([])
 s4 = set(())
 s5 = set()
+s6 = set((1,))
diff --git a/src/flake8_comprehensions/fixes.rs b/src/flake8_comprehensions/fixes.rs
index b94b280fdd..79cc104fc3 100644
--- a/src/flake8_comprehensions/fixes.rs
+++ b/src/flake8_comprehensions/fixes.rs
@@ -258,6 +258,24 @@ pub fn fix_unnecessary_list_comprehension_dict(
     ))
 }
 
+fn drop_trailing_comma<'a>(elements: &[Element<'a>]) -> Vec<Element<'a>> {
+    let mut elements = elements.to_vec();
+    if elements.len() == 1 {
+        if let Some(Element::Simple {
+            value,
+            comma: Some(..),
+            ..
+        }) = elements.last()
+        {
+            elements[0] = Element::Simple {
+                value: value.clone(),
+                comma: None,
+            };
+        }
+    }
+    elements
+}
+
 /// (C405) Convert `set((1, 2))` to `{1, 2}`.
 pub fn fix_unnecessary_literal_set(locator: &Locator, expr: &rustpython_ast::Expr) -> Result<Fix> {
     // Expr(Call(List|Tuple)))) -> Expr(Set)))
@@ -268,8 +286,8 @@ pub fn fix_unnecessary_literal_set(locator: &Locator, expr: &rustpython_ast::Exp
     let arg = match_arg(call)?;
 
     let elements = match &arg.value {
-        Expression::Tuple(inner) => &inner.elements,
-        Expression::List(inner) => &inner.elements,
+        Expression::Tuple(inner) => drop_trailing_comma(&inner.elements),
+        Expression::List(inner) => inner.elements.clone(),
         _ => {
             bail!("Expected Expression::Tuple | Expression::List");
         }
@@ -279,7 +297,7 @@ pub fn fix_unnecessary_literal_set(locator: &Locator, expr: &rustpython_ast::Exp
         call.args = vec![];
     } else {
         body.value = Expression::Set(Box::new(Set {
-            elements: elements.clone(),
+            elements,
             lbrace: LeftCurlyBrace {
                 whitespace_after: call.whitespace_before_args.clone(),
             },
diff --git a/src/flake8_comprehensions/snapshots/ruff__flake8_comprehensions__tests__C405_C405.py.snap b/src/flake8_comprehensions/snapshots/ruff__flake8_comprehensions__tests__C405_C405.py.snap
index d16f4e3084..46f36e2a4a 100644
--- a/src/flake8_comprehensions/snapshots/ruff__flake8_comprehensions__tests__C405_C405.py.snap
+++ b/src/flake8_comprehensions/snapshots/ruff__flake8_comprehensions__tests__C405_C405.py.snap
@@ -1,6 +1,6 @@
 ---
 source: src/flake8_comprehensions/mod.rs
-expression: checks
+expression: diagnostics
 ---
 - kind:
     UnnecessaryLiteralSet: list
@@ -70,4 +70,21 @@ expression: checks
       row: 4
       column: 12
   parent: ~
+- kind:
+    UnnecessaryLiteralSet: tuple
+  location:
+    row: 6
+    column: 5
+  end_location:
+    row: 6
+    column: 14
+  fix:
+    content: "{1}"
+    location:
+      row: 6
+      column: 5
+    end_location:
+      row: 6
+      column: 14
+  parent: ~