From 53f6b8349a56e43ee2f84115efac10ceae625406 Mon Sep 17 00:00:00 2001
From: Ran Benita <ran@unusedvar.com>
Date: Thu, 9 Nov 2023 23:20:28 +0200
Subject: [PATCH] Format one-tuples and one-subscripts as multi-line if already
 multi-line

Fix #3918.
---
 src/black/lines.py                            | 13 +++++--
 tests/data/cases/collections.py               | 36 +++++++++++++++++++
 tests/data/cases/one_element_subscript.py     | 22 ++++++++++--
 tests/data/cases/skip_magic_trailing_comma.py | 12 +++++++
 4 files changed, 79 insertions(+), 4 deletions(-)

diff --git a/src/black/lines.py b/src/black/lines.py
index 20f22acf93a..995c3da82f6 100644
--- a/src/black/lines.py
+++ b/src/black/lines.py
@@ -337,6 +337,9 @@ def has_magic_trailing_comma(
         - there's a trailing comma here
         - it's not a one-tuple
         - it's not a single-element subscript
+        Additionally, if not ensure_removable:
+        - it's a one-tuple or single-element subscript that is already
+          split to multiple lines
         """
         if not (
             closing.type in CLOSING_BRACKETS
@@ -360,7 +363,10 @@ def has_magic_trailing_comma(
                     brackets=(token.LSQB, token.RSQB),
                 )
             ):
-                return False
+                return (
+                    closing.opening_bracket.lineno != closing.lineno
+                    and not ensure_removable
+                )
 
             return True
 
@@ -374,7 +380,10 @@ def has_magic_trailing_comma(
                 self.leaves,
                 brackets=(token.LPAR, token.RPAR),
             ):
-                return False
+                return (
+                    closing.opening_bracket.lineno != closing.lineno
+                    and not ensure_removable
+                )
 
             return True
 
diff --git a/tests/data/cases/collections.py b/tests/data/cases/collections.py
index 68431665211..e8dc8b09225 100644
--- a/tests/data/cases/collections.py
+++ b/tests/data/cases/collections.py
@@ -37,6 +37,9 @@
 ['ls', 'lsoneple/%s' % (foo,)]
 x = {"oneple": (1,)}
 y = {"oneple": (1,),}
+z = {"oneple": (
+    1,
+)}
 assert False, ("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa wraps %s" % bar)
 
 # looping over a 1-tuple should also not get wrapped
@@ -45,6 +48,18 @@
 for (x,) in (1,), (2,), (3,):
     pass
 
+(1,)
+(
+    1,
+)
+[1,]
+[
+    1,
+]
+{1,}
+{
+    1,
+}
 [1, 2, 3,]
 
 division_result_tuple = (6/2,)
@@ -127,6 +142,11 @@
 y = {
     "oneple": (1,),
 }
+z = {
+    "oneple": (
+        1,
+    )
+}
 assert False, (
     "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa wraps %s"
     % bar
@@ -138,6 +158,22 @@
 for (x,) in (1,), (2,), (3,):
     pass
 
+(1,)
+(
+    1,
+)
+[
+    1,
+]
+[
+    1,
+]
+{
+    1,
+}
+{
+    1,
+}
 [
     1,
     2,
diff --git a/tests/data/cases/one_element_subscript.py b/tests/data/cases/one_element_subscript.py
index 39205ba9f7a..4fe8a38018e 100644
--- a/tests/data/cases/one_element_subscript.py
+++ b/tests/data/cases/one_element_subscript.py
@@ -1,8 +1,17 @@
 # We should not treat the trailing comma
-# in a single-element subscript.
+# in a single-line single-element subscript.
 a: tuple[int,]
 b = tuple[int,]
 
+# Trailing comma should be preserved on multi-line
+# single-element subscript.
+a: tuple[
+    int,
+]
+b = tuple[
+    int,
+]
+
 # The magic comma still applies to multi-element subscripts.
 c: tuple[int, int,]
 d = tuple[int, int,]
@@ -13,10 +22,19 @@
 
 # output
 # We should not treat the trailing comma
-# in a single-element subscript.
+# in a single-line single-element subscript.
 a: tuple[int,]
 b = tuple[int,]
 
+# Trailing comma should be preserved on multi-line
+# single-element subscript.
+a: tuple[
+    int,
+]
+b = tuple[
+    int,
+]
+
 # The magic comma still applies to multi-element subscripts.
 c: tuple[
     int,
diff --git a/tests/data/cases/skip_magic_trailing_comma.py b/tests/data/cases/skip_magic_trailing_comma.py
index 4dda5df40f0..c9cfde9512a 100644
--- a/tests/data/cases/skip_magic_trailing_comma.py
+++ b/tests/data/cases/skip_magic_trailing_comma.py
@@ -1,7 +1,13 @@
 # flags: --skip-magic-trailing-comma
 # We should not remove the trailing comma in a single-element subscript.
 a: tuple[int,]
+aa: tuple[
+    int,
+]
 b = tuple[int,]
+bb = tuple[
+    int,
+]
 
 # But commas in multiple element subscripts should be removed.
 c: tuple[int, int,]
@@ -15,6 +21,9 @@
 
 # Except single element tuples
 small_tuple = (1,)
+small_multiline_tuple = (
+    1,
+)
 
 # Trailing commas in multiple chained non-nested parens.
 zero(
@@ -50,7 +59,9 @@
 # output
 # We should not remove the trailing comma in a single-element subscript.
 a: tuple[int,]
+aa: tuple[int,]
 b = tuple[int,]
+bb = tuple[int,]
 
 # But commas in multiple element subscripts should be removed.
 c: tuple[int, int]
@@ -64,6 +75,7 @@
 
 # Except single element tuples
 small_tuple = (1,)
+small_multiline_tuple = (1,)
 
 # Trailing commas in multiple chained non-nested parens.
 zero(one).two(three).four(five)