Fix circular dependency with UriHolder by using abstract _clear_uri_set

- instead of abstract _set_uri_set
- removed circular dependency on UriHolder.add_uris

server/entertainment_decider/models/entities.py

@@ -420,9 +420,8 @@ class MediaElement(db.Entity, UriHolder, Tagable):
     def _uri_set(self) -> Set[str]:
         return {m.uri for m in self.__uri_list}
 
-    def _set_uri_set(self, uri_set: Set[str]) -> None:
+    def _clear_uri_set(self) -> None:
         self.__uri_list = set()
-        self.add_uris(uri_set)
 
     ### for Tagable
 
@@ -749,9 +748,8 @@ class MediaCollection(db.Entity, UriHolder, Tagable):
     def _uri_set(self) -> Set[str]:
         return {m.uri for m in self.__uri_set}
 
-    def _set_uri_set(self, uri_set: Set[str]) -> None:
+    def _clear_uri_set(self) -> None:
         self.__uri_set = set()
-        self.add_uris(uri_set)
 
     ### for Tagable
 

server/entertainment_decider/models/extras/uris.py

@@ -20,7 +20,7 @@ class UriHolder:
         """Returns the uri set of this object in a naive way."""
 
     @abstractmethod
-    def _set_uri_set(self, uri_set: Set[str]) -> None:
+    def _clear_uri_set(self) -> None:
         """Sets the uri set of this object in a naive way."""
 
     @abstractmethod
@@ -72,8 +72,8 @@ class UriHolder:
         return ret
 
     def set_as_only_uri(self, uri: str) -> None:
-        self._set_uri_set({uri})  # might fail, so try first
-        self._set_primary_uri(uri)
+        self._clear_uri_set()
+        self.set_primary_uri(uri)
 
     def add_single_uri(self, uri: str) -> bool:
         return self._add_uri_to_set(uri)