From 820f38708fd41a1b992716b1f65c9b0656f589d0 Mon Sep 17 00:00:00 2001
From: David Szotten <davidszotten@gmail.com>
Date: Fri, 14 Aug 2020 17:17:56 +0100
Subject: [PATCH] fix unary op detection (#1600)

---
 src/black/__init__.py            | 20 ++++++++++----------
 tests/data/percent_precedence.py |  2 ++
 2 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/src/black/__init__.py b/src/black/__init__.py
index b660e47..391233e 100644
--- a/src/black/__init__.py
+++ b/src/black/__init__.py
@@ -3297,12 +3297,12 @@ class StringParenStripper(StringTransformer):
             # if the leaves in the parsed string include a PERCENT, we need to
             # make sure the initial LPAR is NOT preceded by an operator with
             # higher or equal precedence to PERCENT
-            if (
-                is_valid_index(idx - 2)
-                and token.PERCENT in {leaf.type for leaf in LL[idx - 1 : next_idx]}
-                and (
+            if is_valid_index(idx - 2):
+                # mypy can't quite follow unless we name this
+                before_lpar = LL[idx - 2]
+                if token.PERCENT in {leaf.type for leaf in LL[idx - 1 : next_idx]} and (
                     (
-                        LL[idx - 2].type
+                        before_lpar.type
                         in {
                             token.STAR,
                             token.AT,
@@ -3318,12 +3318,12 @@ class StringParenStripper(StringTransformer):
                     )
                     or (
                         # only unary PLUS/MINUS
-                        not is_valid_index(idx - 3)
-                        and (LL[idx - 2].type in {token.PLUS, token.MINUS})
+                        before_lpar.parent
+                        and before_lpar.parent.type == syms.factor
+                        and (before_lpar.type in {token.PLUS, token.MINUS})
                     )
-                )
-            ):
-                continue
+                ):
+                    continue
 
             # Should be followed by a non-empty RPAR...
             if (
diff --git a/tests/data/percent_precedence.py b/tests/data/percent_precedence.py
index 44d30f1..b895443 100644
--- a/tests/data/percent_precedence.py
+++ b/tests/data/percent_precedence.py
@@ -12,6 +12,7 @@
 b + ("" % a)
 -("" % a)
 b - ("" % a)
+b + -("" % a)
 ~("" % a)
 2 ** ("" % a)
 await ("" % a)
@@ -32,6 +33,7 @@ b(("" % a))
 b + "" % a
 -("" % a)
 b - "" % a
+b + -("" % a)
 ~("" % a)
 2 ** ("" % a)
 await ("" % a)
-- 
2.39.2