Fix is_history_shared_with query + test multiple shares with same user

lib/galaxy/managers/histories.py

@@ -342,12 +342,12 @@ class HistoryManager(sharable.SharableModelManager, deletable.PurgableManagerMix
         return extra
 
     def is_history_shared_with(self, history, user) -> bool:
-        return self.session().query(self.user_share_model).filter(
+        return bool(self.session().query(self.user_share_model).filter(
             and_(
                 self.user_share_model.table.c.user_id == user.id,
                 self.user_share_model.table.c.history_id == history.id,
             )
-        ).exists()
+        ).first())
 
 
 class HistoryExportView:

lib/galaxy_test/api/test_histories.py

@@ -534,12 +534,19 @@ class SharingHistoryTestCase(ApiTestCase, BaseHistories, SharingApiTests):
         with self._different_user():
             target_user_id = self.dataset_populator.user_id()
 
+        # Ignore repeated users in the same request
         payload = {"user_ids": [target_user_id, target_user_id]}
         sharing_response = self._share_history_with_payload(history_id, payload)
         assert sharing_response["users_shared_with"]
         assert len(sharing_response["users_shared_with"]) == 1
         assert sharing_response["users_shared_with"][0]["id"] == target_user_id
 
+        # Do not share with the same user multiple times
+        payload = {"user_ids": [target_user_id]}
+        sharing_response = self._share_history_with_payload(history_id, payload)
+        assert sharing_response["errors"]
+        assert "already shared" in sharing_response["errors"][0]
+
     def _share_history_with_payload(self, history_id, payload):
         sharing_response = self._put(f"histories/{history_id}/share_with", data=json.dumps(payload))
         self._assert_status_code_is(sharing_response, 200)