Support sets

Signed-off-by: cobalt <61329810+cobaltt7@users.noreply.github.com>

src/black/linegen.py

@@ -512,11 +512,14 @@ def visit_atom(self, node: Node) -> Iterator[Line]:
         if (
             Preview.remove_lone_list_item_parens in self.mode
             and len(node.children) == 3
-            and node.children[0].type == token.LSQB
-            and node.children[-1].type == token.RSQB
         ):
-            # Lists of one item
-            maybe_make_parens_invisible_in_atom(node.children[1], parent=node)
+            first = node.children[0]
+            last = node.children[-1]
+            if (first.type == token.LSQB and last.type == token.RSQB) or (
+                first.type == token.LBRACE and last.type == token.RBRACE
+            ):
+                # Lists or sets of one item
+                maybe_make_parens_invisible_in_atom(node.children[1], parent=node)
 
         yield from self.visit_default(node)
 

tests/data/cases/preview_remove_lone_list_item_parens.py

@@ -5,6 +5,9 @@
 items = [(((((True,)))))]
 items = [((((()))))]
 items = [(x for x in [1])]
+items = {(123)}
+items = {(True)}
+items = {(((((True)))))}
 
 # Requires `hug_parens_with_braces_and_square_brackets` unstable style to remove parentheses
 # around multiline values
@@ -85,6 +88,9 @@
 items = [(True,)]
 items = [()]
 items = [(x for x in [1])]
+items = {123}
+items = {True}
+items = {True}
 
 # Requires `hug_parens_with_braces_and_square_brackets` unstable style to remove parentheses
 # around multiline values