1 files changed, 39 insertions, 0 deletions
diff --git a/Lib/lib2to3/fixes/fix_ws_comma.py b/Lib/lib2to3/fixes/fix_ws_comma.py
new file mode 100644
index 0000000..2ba1b49
--- /dev/null
+++ b/Lib/lib2to3/fixes/fix_ws_comma.py
@@ -0,0 +1,39 @@
+"""Fixer that changes 'a ,b' into 'a, b'.
+
+This also changes '{a :b}' into '{a: b}', but does not touch other
+uses of colons.  It does not touch other uses of whitespace.
+
+"""
+
+from .. import pytree
+from ..pgen2 import token
+from .import basefix
+
+class FixWsComma(basefix.BaseFix):
+
+  explicit = True # The user must ask for this fixers
+
+  PATTERN = """
+  any<(not(',') any)+ ',' ((not(',') any)+ ',')* [not(',') any]>
+  """
+
+  COMMA = pytree.Leaf(token.COMMA, ",")
+  COLON = pytree.Leaf(token.COLON, ":")
+  SEPS = (COMMA, COLON)
+
+  def transform(self, node, results):
+    new = node.clone()
+    comma = False
+    for child in new.children:
+      if child in self.SEPS:
+        prefix = child.get_prefix()
+        if prefix.isspace() and "\n" not in prefix:
+          child.set_prefix("")
+        comma = True
+      else:
+        if comma:
+          prefix = child.get_prefix()
+          if not prefix:
+            child.set_prefix(" ")
+        comma = False
+    return new