Support facebook return_scopes parameter

CHANGELOG.md

@@ -8,6 +8,8 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 ## [Unreleased](https://github.com/python-social-auth/social-core/commits/master)
 
 ### Added
+- Added support for Facebook OAuth2 return_scopes parameter.
+  Refs [#818](https://github.com/omab/python-social-auth/issues/818)
 - Added support for per-backend USER_FIELDS setting. Refs [#661](https://github.com/omab/python-social-auth/issues/661)
 - Added `expires_in` as `expires` for LinkedIn OAuth2. Refs [#666](https://github.com/omab/python-social-auth/issues/666)
 - Added `SOCIAL_AUTH_USER_AGENT` setting to override the default User-Agent header.

social_core/backends/facebook.py

@@ -29,9 +29,16 @@ class FacebookOAuth2(BaseOAuth2):
     USER_DATA_URL = 'https://graph.facebook.com/v{version}/me'
     EXTRA_DATA = [
         ('id', 'id'),
-        ('expires', 'expires')
+        ('expires', 'expires'),
+        ('granted_scopes', 'granted_scopes'),
+        ('denied_scopes', 'denied_scopes')
     ]
 
+    def auth_params(self, state=None):
+        params = super(FacebookOAuth2, self).auth_params(state)
+        params['return_scopes'] = 'true'
+        return params
+
     def authorization_url(self):
         version = self.setting('API_VERSION', API_VERSION)
         return self.AUTHORIZATION_URL.format(version=version)
@@ -129,6 +136,13 @@ def do_auth(self, access_token, response=None, *args, **kwargs):
         data['access_token'] = access_token
         if 'expires' in response:
             data['expires'] = response['expires']
+
+        if self.data.get('granted_scopes'):
+            data['granted_scopes'] = self.data['granted_scopes'].split(',')
+
+        if self.data.get('denied_scopes'):
+            data['denied_scopes'] = self.data['denied_scopes'].split(',')
+
         kwargs.update({'backend': self, 'response': data})
         return self.strategy.authenticate(*args, **kwargs)