Work around Google Contacts discovery bug (#564)

* Work around Google Contacts discovery bug

* fixup

* changelog

CHANGELOG.rst

@@ -15,6 +15,7 @@ Version 0.15
 - Deprecated syntax for configuration values is now completely rejected. All
   values now have to be valid JSON.
 - A few UX improvements for Google storages, see :gh:`549` and :gh:`552`.
+- Fix collection discovery for :storage:`google_contacts`, see :gh:`564`.
 
 Version 0.14.1
 ==============

vdirsyncer/storage/dav.py

@@ -201,6 +201,23 @@ class Discover(object):
         dav_logger.debug('Given URL is not a homeset URL')
         return self._find_collections_impl(self.find_home())
 
+    def _check_collection_resource_type(self, response):
+        if self._resourcetype is None:
+            return True
+
+        props = _merge_xml(response.findall(
+            '{DAV:}propstat/{DAV:}prop'
+        ))
+        if not props:
+            dav_logger.debug('Skipping, missing <prop>: %s', response)
+            return False
+        if props.find('{DAV:}resourcetype/' + self._resourcetype) \
+           is None:
+            dav_logger.debug('Skipping, not of resource type %s: %s',
+                             self._resourcetype, response)
+            return False
+        return True
+
     def _find_collections_impl(self, url):
         headers = self.session.get_default_headers()
         headers['Depth'] = '1'
@@ -209,13 +226,7 @@ class Discover(object):
         root = _parse_xml(r.content)
         done = set()
         for response in root.findall('{DAV:}response'):
-            props = _merge_xml(response.findall('{DAV:}propstat/{DAV:}prop'))
-            if not props:
-                dav_logger.debug('Skipping, missing <prop>: %s', response)
-                continue
-            if props.find('{DAV:}resourcetype/' + self._resourcetype) is None:
-                dav_logger.debug('Skipping, not of resource type %s: %s',
-                                 self._resourcetype, response)
+            if not self._check_collection_resource_type(response):
                 continue
 
             href = response.find('{DAV:}href')

vdirsyncer/storage/google.py

@@ -164,6 +164,10 @@ class GoogleContactsStorage(dav.CardDAVStorage):
         url = 'https://www.googleapis.com/.well-known/carddav'
         scope = ['https://www.googleapis.com/auth/carddav']
 
+    class discovery_class(dav.CardDAVStorage.discovery_class):
+        # Google CardDAV doesn't return any resourcetype prop.
+        _resourcetype = None
+
     storage_name = 'google_contacts'
 
     def __init__(self, token_file, client_id, client_secret, **kwargs):