Hug parens also with multiline unpacking

CHANGES.md

@@ -14,6 +14,8 @@
 
 - Multiline dictionaries and lists that are the sole argument to a function are now
   indented less (#3964)
+- Multiline list unpacking as the sole argument to a function is now also indented less
+  (#3992)
 
 ### Configuration
 

docs/the_black_code_style/future_style.md

@@ -139,6 +139,26 @@ foo([
 ])
 ```
 
+This also applies to list unpacking:
+
+```python
+foo(
+    *[
+        a_long_function_name(a_long_variable_name)
+        for a_long_variable_name in some_generator
+    ]
+)
+```
+
+will become:
+
+```python
+foo(*[
+    a_long_function_name(a_long_variable_name)
+    for a_long_variable_name in some_generator
+])
+```
+
 You can use a magic trailing comma to avoid this compacting behavior; by default,
 _Black_ will not reformat the following code:
 

src/black/linegen.py

@@ -817,16 +817,17 @@ def _first_right_hand_split(
     head_leaves.reverse()
 
     if Preview.hug_parens_with_braces_and_square_brackets in line.mode:
+        is_unpacking = 1 if body_leaves[0].type == token.STAR else 0
         if (
             tail_leaves[0].type == token.RPAR
             and tail_leaves[0].value
             and tail_leaves[0].opening_bracket is head_leaves[-1]
             and body_leaves[-1].type in [token.RBRACE, token.RSQB]
-            and body_leaves[-1].opening_bracket is body_leaves[0]
+            and body_leaves[-1].opening_bracket is body_leaves[is_unpacking]
         ):
-            head_leaves = head_leaves + body_leaves[:1]
+            head_leaves = head_leaves + body_leaves[: 1 + is_unpacking]
             tail_leaves = body_leaves[-1:] + tail_leaves
-            body_leaves = body_leaves[1:-1]
+            body_leaves = body_leaves[1 + is_unpacking : -1]
 
     head = bracket_split_build_line(
         head_leaves, line, opening_bracket, component=_BracketSplitComponent.head

tests/data/cases/preview_hug_parens_with_braces_and_square_brackets.py

@@ -137,6 +137,10 @@ def foo_square_brackets(request):
     [1, 2, 3, 4, 5, 6, 7, 8, 9, 10], {x}, "a string", [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
 )
 
+foo(*["long long long long long line", "long long long long long line", "long long long long long line"])
+
+foo(*[str(i) for i in range(100000000000000000000000000000000000000000000000000000000000)])
+
 # output
 def foo_brackets(request):
     return JsonResponse({
@@ -287,3 +291,13 @@ def foo_square_brackets(request):
 baaaaaaaaaaaaar(
     [1, 2, 3, 4, 5, 6, 7, 8, 9, 10], {x}, "a string", [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
 )
+
+foo(*[
+    "long long long long long line",
+    "long long long long long line",
+    "long long long long long line",
+])
+
+foo(*[
+    str(i) for i in range(100000000000000000000000000000000000000000000000000000000000)
+])