[ruff] Fix ISC003 autofix incorrectly stripping + from comments

crates/ruff_linter/resources/test/fixtures/flake8_implicit_str_concat/ISC.py

@@ -222,3 +222,12 @@
     "abc"
     "def"
 ) + "ghi"
+
+
+# https://github.com/astral-sh/ruff/issues/26541
+x = (
+    "A"  # Complains about this: +
+    + " broken"
+    + " line"
+    + " string."
+)

crates/ruff_linter/src/rules/flake8_implicit_str_concat/rules/explicit.rs

@@ -1,5 +1,5 @@
 use ruff_macros::{ViolationMetadata, derive_message_formats};
-use ruff_python_ast::token::parenthesized_range;
+use ruff_python_ast::token::{TokenKind, parenthesized_range};
 use ruff_python_ast::{self as ast, Expr, Operator};
 use ruff_python_trivia::is_python_whitespace;
 use ruff_source_file::LineRanges;
@@ -105,18 +105,30 @@ pub(crate) fn explicit(checker: &Checker, expr: &Expr) {
                     return;
                 }
 
-                diagnostic.set_fix(generate_fix(checker, bin_op));
+                if let Some(fix) = generate_fix(checker, bin_op) {
+                    diagnostic.set_fix(fix);
+                }
             }
         }
     }
 }
 
-fn generate_fix(checker: &Checker, expr_bin_op: &ast::ExprBinOp) -> Fix {
+fn generate_fix(checker: &Checker, expr_bin_op: &ast::ExprBinOp) -> Option<Fix> {
     let ast::ExprBinOp { left, right, .. } = expr_bin_op;
 
     let between_operands_range = TextRange::new(left.end(), right.start());
-    let between_operands = checker.locator().slice(between_operands_range);
-    let (before_plus, after_plus) = between_operands.split_once('+').unwrap();
+    let plus_token = checker
+        .tokens()
+        .in_range(between_operands_range)
+        .iter()
+        .find(|token| token.kind() == TokenKind::Plus)?;
+
+    let before_plus = checker
+        .locator()
+        .slice(TextRange::new(left.end(), plus_token.start()));
+    let after_plus = checker
+        .locator()
+        .slice(TextRange::new(plus_token.end(), right.start()));
 
     let linebreak_before_operator =
         before_plus.contains_line_break(TextRange::at(TextSize::new(0), before_plus.text_len()));
@@ -129,8 +141,8 @@ fn generate_fix(checker: &Checker, expr_bin_op: &ast::ExprBinOp) -> Fix {
         before_plus.trim_end_matches(is_python_whitespace)
     };
 
-    Fix::safe_edit(Edit::range_replacement(
+    Some(Fix::safe_edit(Edit::range_replacement(
         format!("{before_plus}{after_plus}"),
         between_operands_range,
-    ))
+    )))
 }

crates/ruff_linter/src/rules/flake8_implicit_str_concat/snapshots/ruff_linter__rules__flake8_implicit_str_concat__tests__ISC003_ISC.py.snap

@@ -351,3 +351,22 @@ ISC003 Explicitly concatenated string should be implicitly concatenated
     | |_________^
     |
 help: Remove redundant '+' operator to implicitly concatenate
+
+ISC003 [*] Explicitly concatenated string should be implicitly concatenated
+   --> ISC.py:229:5
+    |
+227 |   # https://github.com/astral-sh/ruff/issues/26541
+228 |   x = (
+229 | /     "A"  # Complains about this: +
+230 | |     + " broken"
+    | |_______________^
+231 |       + " line"
+232 |       + " string."
+    |
+help: Remove redundant '+' operator to implicitly concatenate
+    |
+229 |     "A"  # Complains about this: +
+    -     + " broken"
+230 +      " broken"
+231 |     + " line"
+    |