Filter by stoken: cleanup and fix the done implementation

The done implementation wasn't great because it would indicate we are
not done even when we are when the last chunk returned is exactly the
size of limit.

django_etebase/views.py

@@ -119,7 +119,7 @@ class BaseViewSet(viewsets.ModelViewSet):
             maxid = max(maxid, rowmaxid)
         new_stoken = (maxid >= 0) and Stoken.objects.get(id=maxid).uid
 
-        return queryset, new_stoken
+        return new_stoken
 
     def filter_by_stoken_and_limit(self, request, queryset):
         limit = int(request.GET.get('limit', 50))
@@ -127,13 +127,16 @@ class BaseViewSet(viewsets.ModelViewSet):
         queryset, stoken_rev = self.filter_by_stoken(request, queryset)
         stoken = stoken_rev.uid if stoken_rev is not None else None
 
-        queryset = queryset[:limit]
-        queryset, new_stoken = self.get_queryset_stoken(queryset)
-        new_stoken = new_stoken or stoken
-        # This is not the most efficient way of implementing this, but it's good enough
-        done = len(queryset) < limit
+        result = list(queryset[:limit + 1])
+        if len(result) < limit + 1:
+            done = True
+        else:
+            done = False
+            result = result[:-1]
+
+        new_stoken = self.get_queryset_stoken(result) or stoken
 
-        return queryset, new_stoken, done
+        return result, new_stoken, done
 
     # Change how our list works by default
     def list(self, request, collection_uid=None):
@@ -193,9 +196,9 @@ class CollectionViewSet(BaseViewSet):
 
     def list(self, request):
         queryset = self.get_queryset()
-        queryset, new_stoken, done = self.filter_by_stoken_and_limit(request, queryset)
+        result, new_stoken, done = self.filter_by_stoken_and_limit(request, queryset)
 
-        serializer = self.get_serializer(queryset, many=True)
+        serializer = self.get_serializer(result, many=True)
 
         ret = {
             'data': serializer.data,
@@ -260,9 +263,9 @@ class CollectionItemViewSet(BaseViewSet):
         if not self.request.query_params.get('withCollection', False):
             queryset = queryset.filter(parent__isnull=True)
 
-        queryset, new_stoken, done = self.filter_by_stoken_and_limit(request, queryset)
+        result, new_stoken, done = self.filter_by_stoken_and_limit(request, queryset)
 
-        serializer = self.get_serializer(queryset, many=True)
+        serializer = self.get_serializer(result, many=True)
 
         ret = {
             'data': serializer.data,
@@ -321,7 +324,7 @@ class CollectionItemViewSet(BaseViewSet):
             revs = CollectionItemRevision.objects.filter(uid__in=etags, current=True)
             queryset = queryset.filter(uid__in=uids).exclude(revisions__in=revs)
 
-            queryset, new_stoken = self.get_queryset_stoken(queryset)
+            new_stoken = self.get_queryset_stoken(queryset)
             stoken = stoken_rev and stoken_rev.uid
             new_stoken = new_stoken or stoken
 
@@ -461,8 +464,8 @@ class CollectionMemberViewSet(BaseViewSet):
 
     def list(self, request, collection_uid=None):
         queryset = self.get_queryset().order_by('id')
-        queryset, new_stoken, done = self.filter_by_stoken_and_limit(request, queryset)
-        serializer = self.get_serializer(queryset, many=True)
+        result, new_stoken, done = self.filter_by_stoken_and_limit(request, queryset)
+        serializer = self.get_serializer(result, many=True)
 
         ret = {
             'data': serializer.data,