From 84f7ba686a2b27e302ea6eae29d7dc9d0023a2a0 Mon Sep 17 00:00:00 2001
From: Rishav Kundu <rk@rishav.io>
Date: Tue, 5 Jan 2021 22:20:34 +0530
Subject: [PATCH] Strip redundant parentheses from assignment exprs

Addresses #1656
---
 src/black/__init__.py       | 8 ++++----
 tests/data/pep_572.py       | 4 ++--
 tests/data/remove_parens.py | 7 +++++++
 3 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/src/black/__init__.py b/src/black/__init__.py
index 07251d55fb5..a81f35acbc1 100644
--- a/src/black/__init__.py
+++ b/src/black/__init__.py
@@ -5368,10 +5368,7 @@ def normalize_invisible_parens(node: Node, parens_after: Set[str]) -> None:
             check_lpar = True
 
         if check_lpar:
-            if is_walrus_assignment(child):
-                pass
-
-            elif child.type == syms.atom:
+            if child.type == syms.atom:
                 if maybe_make_parens_invisible_in_atom(child, parent=node):
                     wrap_in_parentheses(node, child, visible=False)
             elif is_one_tuple(child):
@@ -5549,6 +5546,9 @@ def maybe_make_parens_invisible_in_atom(node: LN, parent: LN) -> bool:
         or is_one_tuple(node)
         or (is_yield(node) and parent.type != syms.expr_stmt)
         or max_delimiter_priority_in_atom(node) >= COMMA_PRIORITY
+        or parent.type == syms.expr_stmt
+        and parent.children[1].type == token.EQUAL
+        and is_walrus_assignment(node)
     ):
         return False
 
diff --git a/tests/data/pep_572.py b/tests/data/pep_572.py
index 637b3bb38c6..c6867f26258 100644
--- a/tests/data/pep_572.py
+++ b/tests/data/pep_572.py
@@ -2,7 +2,7 @@
 (a := a)
 if (match := pattern.search(data)) is None:
     pass
-if (match := pattern.search(data)):
+if match := pattern.search(data):
     pass
 [y := f(x), y ** 2, y ** 3]
 filtered_data = [y for x in data if (y := f(x)) is None]
@@ -43,5 +43,5 @@ def foo(answer: (p := 42) = 5):
 
 while x := f(x):
     pass
-while (x := f(x)):
+while x := f(x):
     pass
diff --git a/tests/data/remove_parens.py b/tests/data/remove_parens.py
index afc34010c30..7054467c9ab 100644
--- a/tests/data/remove_parens.py
+++ b/tests/data/remove_parens.py
@@ -54,6 +54,9 @@ def example7():
 def example8():
     return (((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((None)))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))
 
+def example9():
+    if (foo := 0):
+        pass
 
 # output
 x = 1
@@ -142,3 +145,7 @@ def example7():
 def example8():
     return None
 
+
+def example9():
+    if foo := 0:
+        pass