Fix numpy-style array indexing

Fixes pytest-dev#33

Author: ambv

black.py

@@ -960,7 +960,14 @@ def whitespace(leaf: Leaf) -> str:
 
     elif p.type == syms.subscript:
         # indexing
-        if not prev or prev.type == token.COLON:
+        if not prev:
+            assert p.parent is not None, "subscripts are always parented"
+            if p.parent.type == syms.subscriptlist:
+                return SPACE
+
+            return NO
+
+        elif prev.type == token.COLON:
             return NO
 
     elif p.type == syms.atom:

tests/expression.py

@@ -88,6 +88,7 @@
 slice[:-1]
 slice[1:]
 slice[::-1]
+numpy[:, 0:1]
 (str or None) if (sys.version_info[0] > (3,)) else (str or bytes or None)
 {'2.7': dead, '3.7': long_live or die_hard}
 {'2.7', '3.6', '3.7', '3.8', '3.9', '4.0' if gilectomy else '3.10'}
@@ -219,6 +220,7 @@ async def f():
 slice[:-1]
 slice[1:]
 slice[::-1]
+numpy[:, 0:1]
 (str or None) if (sys.version_info[0] > (3,)) else (str or bytes or None)
 {'2.7': dead, '3.7': long_live or die_hard}
 {'2.7', '3.6', '3.7', '3.8', '3.9', '4.0' if gilectomy else '3.10'}