[pycodestyle] Fix E731 autofix creating a syntax error for expressions spanned across multiple lines (#18479)

crates/ruff_linter/src/rules/pycodestyle/rules/lambda_assignment.rs

@@ -92,7 +92,7 @@ pub(crate) fn lambda_assignment(
         let first_line = checker.locator().line_str(stmt.start());
         let indentation = leading_indentation(first_line);
         let mut indented = String::new();
-        for (idx, line) in function(id, lambda, annotation, checker)
+        for (idx, line) in function(id, lambda, annotation, stmt, checker)
             .universal_newlines()
             .enumerate()
         {
@@ -177,6 +177,7 @@ fn function(
     name: &str,
     lambda: &ExprLambda,
     annotation: Option<&Expr>,
+    stmt: &Stmt,
     checker: &Checker,
 ) -> String {
     // Use a dummy body. It gets replaced at the end with the actual body.
@@ -236,7 +237,7 @@ fn function(
             });
             let generated = checker.generator().stmt(&func);
 
-            return replace_trailing_ellipsis_with_original_expr(generated, lambda, checker);
+            return replace_trailing_ellipsis_with_original_expr(generated, lambda, stmt, checker);
         }
     }
     let function = Stmt::FunctionDef(ast::StmtFunctionDef {
@@ -251,12 +252,13 @@ fn function(
     });
     let generated = checker.generator().stmt(&function);
 
-    replace_trailing_ellipsis_with_original_expr(generated, lambda, checker)
+    replace_trailing_ellipsis_with_original_expr(generated, lambda, stmt, checker)
 }
 
 fn replace_trailing_ellipsis_with_original_expr(
     mut generated: String,
     lambda: &ExprLambda,
+    stmt: &Stmt,
     checker: &Checker,
 ) -> String {
     let original_expr_range = parenthesized_range(
@@ -267,14 +269,28 @@ fn replace_trailing_ellipsis_with_original_expr(
     )
     .unwrap_or(lambda.body.range());
 
-    let original_expr_in_source = checker.locator().slice(original_expr_range);
+    // This prevents the autofix of introducing a syntax error if the lambda's body is an
+    // expression spanned across multiple lines. To avoid the syntax error we preserve
+    // the parenthesis around the body.
+    let original_expr_in_source = if parenthesized_range(
+        lambda.into(),
+        stmt.into(),
+        checker.comment_ranges(),
+        checker.source(),
+    )
+    .is_some()
+    {
+        format!("({})", checker.locator().slice(original_expr_range))
+    } else {
+        checker.locator().slice(original_expr_range).to_string()
+    };
 
     let placeholder_ellipsis_start = generated.rfind("...").unwrap();
     let placeholder_ellipsis_end = placeholder_ellipsis_start + "...".len();
 
     generated.replace_range(
         placeholder_ellipsis_start..placeholder_ellipsis_end,
-        original_expr_in_source,
+        &original_expr_in_source,
     );
     generated
 }

crates/ruff_linter/src/rules/pycodestyle/snapshots/ruff_linter__rules__pycodestyle__tests__E731_E731.py.snap

@@ -318,7 +318,7 @@ E731.py:139:5: E731 Do not assign a `lambda` expression, use a `def`
 138 138 | class TemperatureScales(Enum):
 139     |-    CELSIUS = (lambda deg_c: deg_c)
     139 |+    def CELSIUS(deg_c):
-    140 |+        return deg_c
+    140 |+        return (deg_c)
 140 141 |     FAHRENHEIT = (lambda deg_c: deg_c * 9 / 5 + 32)
 141 142 | 
 142 143 | 
@@ -338,7 +338,7 @@ E731.py:140:5: E731 Do not assign a `lambda` expression, use a `def`
 139 139 |     CELSIUS = (lambda deg_c: deg_c)
 140     |-    FAHRENHEIT = (lambda deg_c: deg_c * 9 / 5 + 32)
     140 |+    def FAHRENHEIT(deg_c):
-    141 |+        return deg_c * 9 / 5 + 32
+    141 |+        return (deg_c * 9 / 5 + 32)
 141 142 | 
 142 143 | 
 143 144 | # Regression test for: https://github.com/astral-sh/ruff/issues/7141
@@ -449,6 +449,8 @@ E731.py:176:1: E731 [*] Do not assign a `lambda` expression, use a `def`
 178 | |     y := 10
 179 | | )
     | |_^ E731
+180 |
+181 |   # https://github.com/astral-sh/ruff/issues/18475
     |
     = help: Rewrite `x` as a `def`
 
@@ -462,3 +464,59 @@ E731.py:176:1: E731 [*] Do not assign a `lambda` expression, use a `def`
 177 178 |     # comment
 178 179 |     y := 10
 179 180 | )
+
+E731.py:182:1: E731 [*] Do not assign a `lambda` expression, use a `def`
+    |
+181 |   # https://github.com/astral-sh/ruff/issues/18475
+182 | / foo_tooltip = (
+183 | |     lambda x, data: f"\nfoo: {data['foo'][int(x)]}"
+184 | |     if data["foo"] is not None
+185 | |     else ""
+186 | | )
+    | |_^ E731
+187 |
+188 |   foo_tooltip = (
+    |
+    = help: Rewrite `foo_tooltip` as a `def`
+
+ℹ Unsafe fix
+179 179 | )
+180 180 | 
+181 181 | # https://github.com/astral-sh/ruff/issues/18475
+182     |-foo_tooltip = (
+183     |-    lambda x, data: f"\nfoo: {data['foo'][int(x)]}"
+    182 |+def foo_tooltip(x, data):
+    183 |+    return (f"\nfoo: {data['foo'][int(x)]}"
+184 184 |     if data["foo"] is not None
+185     |-    else ""
+186     |-)
+    185 |+    else "")
+187 186 | 
+188 187 | foo_tooltip = (
+189 188 |     lambda x, data: f"\nfoo: {data['foo'][int(x)]}" +
+
+E731.py:188:1: E731 [*] Do not assign a `lambda` expression, use a `def`
+    |
+186 |   )
+187 |
+188 | / foo_tooltip = (
+189 | |     lambda x, data: f"\nfoo: {data['foo'][int(x)]}" +
+190 | |     more
+191 | |
+192 | | )
+    | |_^ E731
+    |
+    = help: Rewrite `foo_tooltip` as a `def`
+
+ℹ Unsafe fix
+185 185 |     else ""
+186 186 | )
+187 187 | 
+188     |-foo_tooltip = (
+189     |-    lambda x, data: f"\nfoo: {data['foo'][int(x)]}" +
+190     |-    more
+191     |-
+192     |-)
+    188 |+def foo_tooltip(x, data):
+    189 |+    return (f"\nfoo: {data['foo'][int(x)]}" +
+    190 |+    more)