Recursively unwrap tuples in del statements

CHANGES.md

@@ -9,6 +9,7 @@
 ### Stable style
 
 <!-- Changes that affect Black's stable style -->
+- Fix crash while formatting a long `del` statement containing tuples (#4628)
 
 ### Preview style
 

src/black/parsing.py

@@ -213,7 +213,7 @@ def _stringify_ast(node: ast.AST, parent_stack: list[ast.AST]) -> Iterator[str]:
                     and isinstance(node, ast.Delete)
                     and isinstance(item, ast.Tuple)
                 ):
-                    for elt in item.elts:
+                    for elt in _unwrap_tuples(item):
                         yield from _stringify_ast_with_new_parent(
                             elt, parent_stack, node
                         )
@@ -250,3 +250,11 @@ def _stringify_ast(node: ast.AST, parent_stack: list[ast.AST]) -> Iterator[str]:
             )
 
     yield f"{'    ' * len(parent_stack)})  # /{node.__class__.__name__}"
+
+
+def _unwrap_tuples(node: ast.Tuple) -> Iterator[ast.AST]:
+    for elt in node.elts:
+        if isinstance(elt, ast.Tuple):
+            yield from _unwrap_tuples(elt)
+        else:
+            yield elt

tests/data/cases/cantfit.py

@@ -31,7 +31,8 @@
         raise ValueError(err.format(key))
 concatenated_strings = "some strings that are " "concatenated implicitly, so if you put them on separate " "lines it will fit"
 del concatenated_strings, string_variable_name, normal_function_name, normal_name, need_more_to_make_the_line_long_enough
-
+del ([], name_1, name_2), [(), [], name_4, name_3], name_1[[name_2 for name_1 in name_0]]
+del (),
 
 # output
 
@@ -91,3 +92,9 @@
     normal_name,
     need_more_to_make_the_line_long_enough,
 )
+del (
+    ([], name_1, name_2),
+    [(), [], name_4, name_3],
+    name_1[[name_2 for name_1 in name_0]],
+)
+del ((),)