Fix bug in counting backspaces

awscli/compat.py

@@ -226,11 +226,12 @@ def _windows_shell_quote(s):
             # they will need to be escaped. Instead we separately keep track
             # of how many we've seen.
             num_backspaces += 1
-        if character == '"':
+        elif character == '"':
             if num_backspaces > 0:
                 # The backslashes are part of a chain that lead up to a
                 # double quote, so they need to be escaped.
                 buff.append('\\' * (num_backspaces * 2))
+                num_backspaces = 0
 
             # The double quote also needs to be escaped. The fact that we're
             # seeing it at all means that it must have been escaped in the
@@ -245,6 +246,11 @@ def _windows_shell_quote(s):
                 num_backspaces = 0
             buff.append(character)
 
+    # There may be some leftover backspaces if they were on the trailing
+    # end, so they're added back in here.
+    if num_backspaces > 0:
+        buff.append('\\' * num_backspaces)
+
     new_s = ''.join(buff)
     if ' ' in new_s or '\t' in new_s:
         # If there are any spaces or tabs then the string needs to be double

tests/unit/test_compat.py

@@ -53,7 +53,9 @@ def test_compat_shell_quote_windows():
     windows_cases = {
         '': '""',
         '"': '\\"',
-        '\\': '\\\\',
+        '\\': '\\',
+        '\\a': '\\a',
+        '\\\\': '\\\\',
         '\\"': '\\\\\\"',
         '\\\\"': '\\\\\\\\\\"',
         'foo bar': '"foo bar"',