Prevent converting numbers with leading zeroes to int. (#390) (#405)

* Prevent converting numbers with leading zeroes to int.
* But do treat a single 0 as an int.

imapclient/response_parser.py

@@ -215,7 +215,8 @@ def atom(src, token):
         return literal_text
     elif len(token) >= 2 and (token[:1] == token[-1:] == b'"'):
         return token[1:-1]
-    elif token.isdigit():
+    elif token.isdigit() and (token[:1] != b'0' or len(token) == 1):
+        # this prevents converting items like 0123 to 123
         return int(token)
     else:
         return token

tests/test_response_parser.py

@@ -41,6 +41,12 @@ def test_string(self):
     def test_int(self):
         self._test(b'45', 45)
 
+    def test_int_zero(self):
+        self._test(b'0', 0)
+
+    def test_not_an_int(self):
+        self._test(b'0123', b'0123')
+
     def test_nil(self):
         self._test(b'NIL', None)