Fix an issue with non-dict values in flow exchange.

The OAuth2 for Devices implementation picked up an incidental change that
failed to treat dicts and dict-like objects the same way. This is particularly
painful in environments like App Engine, where `self.request.params` is a
common dict-like value to pass in.

This restores the previous behavior, and adds a test.

oauth2client/client.py

@@ -1767,10 +1767,10 @@ class OAuth2WebServerFlow(Flow):
 
     Args:
 
-      code: string, dict or None. For a non-device flow, this is
-          either the response code as a string, or a dictionary of
-          query parameters to the redirect_uri. For a device flow,
-          this should be None.
+      code: string, a dict-like object, or None. For a non-device
+          flow, this is either the response code as a string, or a
+          dictionary of query parameters to the redirect_uri. For a
+          device flow, this should be None.
       http: httplib2.Http, optional http instance to use when fetching
           credentials.
       device_flow_info: DeviceFlowInfo, return value from step1 in the
@@ -1793,7 +1793,7 @@ class OAuth2WebServerFlow(Flow):
 
     if code is None:
       code = device_flow_info.device_code
-    elif isinstance(code, dict):
+    elif not isinstance(code, basestring):
       if 'code' not in code:
         raise FlowExchangeError(code.get(
             'error', 'No code was supplied in the query parameters.'))

tests/http_mock.py

@@ -90,6 +90,7 @@ class HttpMockSequence(object):
     """
     self._iterable = iterable
     self.follow_redirects = True
+    self.requests = []
 
   def request(self, uri,
               method='GET',
@@ -98,6 +99,7 @@ class HttpMockSequence(object):
               redirections=1,
               connection_type=None):
     resp, content = self._iterable.pop(0)
+    self.requests.append({'uri': uri, 'body': body, 'headers': headers})
     if content == 'echo_request_headers':
       content = headers
     elif content == 'echo_request_headers_as_json':

tests/test_oauth2client.py

@@ -875,6 +875,34 @@ class OAuth2WebServerFlowTest(unittest.TestCase):
     self.assertEqual('8xLOxBtZp8', credentials.refresh_token)
     self.assertEqual('dummy_revoke_uri', credentials.revoke_uri)
 
+  def test_exchange_dictlike(self):
+    class FakeDict(object):
+      def __init__(self, d):
+        self.d = d
+
+      def __getitem__(self, name):
+        return self.d[name]
+
+      def __contains__(self, name):
+        return name in self.d
+
+    code = 'some random code'
+    not_a_dict = FakeDict({'code': code})
+    http = HttpMockSequence([
+      ({'status': '200'},
+      """{ "access_token":"SlAV32hkKG",
+       "expires_in":3600,
+       "refresh_token":"8xLOxBtZp8" }"""),
+      ])
+
+    credentials = self.flow.step2_exchange(not_a_dict, http=http)
+    self.assertEqual('SlAV32hkKG', credentials.access_token)
+    self.assertNotEqual(None, credentials.token_expiry)
+    self.assertEqual('8xLOxBtZp8', credentials.refresh_token)
+    self.assertEqual('dummy_revoke_uri', credentials.revoke_uri)
+    request_code = urlparse.parse_qs(http.requests[0]['body'])['code'][0]
+    self.assertEqual(code, request_code)
+
   def test_urlencoded_exchange_success(self):
     http = HttpMockSequence([
       ({'status': '200'}, 'access_token=SlAV32hkKG&expires_in=3600'),