From 92b377556e24616d5980a9010cf558da7fa35d28 Mon Sep 17 00:00:00 2001
From: =?utf8?q?=C5=81ukasz=20Langa?= <lukasz@langa.pl>
Date: Wed, 21 Mar 2018 18:23:46 -0700
Subject: [PATCH] Don't omit whitespace when the factor is not a math operator

Fixes #55
---
 README.md           | 5 +++++
 black.py            | 7 ++++++-
 tests/expression.py | 4 ++++
 3 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/README.md b/README.md
index 20ab4be..aba30ab 100644
--- a/README.md
+++ b/README.md
@@ -293,6 +293,11 @@ More details can be found in [CONTRIBUTING](CONTRIBUTING.md).
 
 ## Change Log
 
+### 18.3a4 (unreleased)
+
+* don't omit whitespace if the previous factor leaf wasn't a math
+  operator (#55)
+
 ### 18.3a3
 
 * don't remove single empty lines outside of bracketed expressions
diff --git a/black.py b/black.py
index 1c07de7..0dd7630 100644
--- a/black.py
+++ b/black.py
@@ -340,6 +340,7 @@ MATH_OPERATORS = {
     token.AMPER,
     token.PERCENT,
     token.CIRCUMFLEX,
+    token.TILDE,
     token.LEFTSHIFT,
     token.RIGHTSHIFT,
     token.DOUBLESTAR,
@@ -888,7 +889,11 @@ def whitespace(leaf: Leaf) -> str:  # noqa C901
             if prevp.parent and prevp.parent.type in {syms.subscript, syms.sliceop}:
                 return NO
 
-        elif prevp.parent and prevp.parent.type in {syms.factor, syms.star_expr}:
+        elif (
+            prevp.parent
+            and prevp.parent.type in {syms.factor, syms.star_expr}
+            and prevp.type in MATH_OPERATORS
+        ):
             return NO
 
     elif prev.type in OPENING_BRACKETS:
diff --git a/tests/expression.py b/tests/expression.py
index dbb9303..c18942e 100644
--- a/tests/expression.py
+++ b/tests/expression.py
@@ -63,6 +63,8 @@ str or None if (1 if True else 2) else str or bytes or None
 [((i ** 2) + j) for i in (1, 2, 3) for j in (1, 2, 3)]
 {i: 0 for i in (1, 2, 3)}
 {i: j for i, j in ((1, 'a'), (2, 'b'), (3, 'c'))}
+{a: b * 2 for a, b in dictionary.items()}
+{a: b * -2 for a, b in dictionary.items()}
 {k: v for k, v in this_is_a_very_long_variable_which_will_cause_a_trailing_comma_which_breaks_the_comprehension}
 Python3 > Python2 > COBOL
 Life is Life
@@ -214,6 +216,8 @@ str or None if (1 if True else 2) else str or bytes or None
 [((i ** 2) + j) for i in (1, 2, 3) for j in (1, 2, 3)]
 {i: 0 for i in (1, 2, 3)}
 {i: j for i, j in ((1, 'a'), (2, 'b'), (3, 'c'))}
+{a: b * 2 for a, b in dictionary.items()}
+{a: b * -2 for a, b in dictionary.items()}
 {
     k: v
     for k, v in this_is_a_very_long_variable_which_will_cause_a_trailing_comma_which_breaks_the_comprehension
-- 
2.39.5