From de806405d2934b629d67e2a6317ad7e826765a20 Mon Sep 17 00:00:00 2001
From: Jelle Zijlstra <jelle.zijlstra@gmail.com>
Date: Tue, 7 May 2019 09:51:28 -0400
Subject: [PATCH] Add parentheses around tuple unpack assignment (#832)

Fixes #656
---
 black.py                  | 14 +++++++++++++-
 tests/data/tupleassign.py | 10 ++++++++++
 tests/test_black.py       |  8 ++++++++
 3 files changed, 31 insertions(+), 1 deletion(-)
 create mode 100644 tests/data/tupleassign.py

diff --git a/black.py b/black.py
index cada4d0..7bfcfca 100644
--- a/black.py
+++ b/black.py
@@ -2726,6 +2726,14 @@ def normalize_invisible_parens(node: Node, parens_after: Set[str]) -> None:
 
     check_lpar = False
     for index, child in enumerate(list(node.children)):
+        # Add parentheses around long tuple unpacking in assignments.
+        if (
+            index == 0
+            and isinstance(child, Node)
+            and child.type == syms.testlist_star_expr
+        ):
+            check_lpar = True
+
         if check_lpar:
             if child.type == syms.atom:
                 if maybe_make_parens_invisible_in_atom(child, parent=node):
@@ -2757,7 +2765,11 @@ def normalize_invisible_parens(node: Node, parens_after: Set[str]) -> None:
                 lpar = Leaf(token.LPAR, "")
                 rpar = Leaf(token.RPAR, "")
                 index = child.remove() or 0
-                node.insert_child(index, Node(syms.atom, [lpar, child, rpar]))
+                prefix = child.prefix
+                child.prefix = ""
+                new_child = Node(syms.atom, [lpar, child, rpar])
+                new_child.prefix = prefix
+                node.insert_child(index, new_child)
 
         check_lpar = isinstance(child, Leaf) and child.value in parens_after
 
diff --git a/tests/data/tupleassign.py b/tests/data/tupleassign.py
new file mode 100644
index 0000000..c0debd7
--- /dev/null
+++ b/tests/data/tupleassign.py
@@ -0,0 +1,10 @@
+sdfjklsdfsjldkflkjsf, sdfjsdfjlksdljkfsdlkf, sdfsdjfklsdfjlksdljkf, sdsfsdfjskdflsfsdf = 1, 2, 3
+
+
+# output
+(
+    sdfjklsdfsjldkflkjsf,
+    sdfjsdfjlksdljkfsdlkf,
+    sdfsdjfklsdfjlksdljkf,
+    sdsfsdfjskdflsfsdf,
+) = (1, 2, 3)
diff --git a/tests/test_black.py b/tests/test_black.py
index 86175aa..896ad0c 100644
--- a/tests/test_black.py
+++ b/tests/test_black.py
@@ -542,6 +542,14 @@ class BlackTestCase(unittest.TestCase):
         black.assert_equivalent(source, actual)
         black.assert_stable(source, actual, black.FileMode())
 
+    @patch("black.dump_to_file", dump_to_stderr)
+    def test_tuple_assign(self) -> None:
+        source, expected = read_data("tupleassign")
+        actual = fs(source)
+        self.assertFormatEqual(expected, actual)
+        black.assert_equivalent(source, actual)
+        black.assert_stable(source, actual, black.FileMode())
+
     def test_tab_comment_indentation(self) -> None:
         contents_tab = "if 1:\n\tif 2:\n\t\tpass\n\t# comment\n\tpass\n"
         contents_spc = "if 1:\n    if 2:\n        pass\n    # comment\n    pass\n"
-- 
2.39.2