frontend: don't show new action task if namespace is deleting itself

wait for the end of the deletion of project to avoid race
condition when other action like fork or create is called
immidiatelly after delete

frontend/coprs_frontend/coprs/models.py

@@ -2129,6 +2129,7 @@ class Action(db.Model, helpers.Serializer):
     # see ActionTypeEnum
     action_type = db.Column(db.Integer, nullable=False)
     # copr, ...; downcase name of class of modified object
+    # TODO: replace this in the future with something better
     object_type = db.Column(db.String(20))
     # id of the modified object
     object_id = db.Column(db.Integer)

frontend/coprs_frontend/coprs/views/backend_ns/backend_general.py

@@ -1,5 +1,5 @@
 import flask
-from copr_common.enums import StatusEnum
+from copr_common.enums import StatusEnum, ActionTypeEnum
 from coprs import db, app
 from coprs import models
 from coprs.logic import actions_logic
@@ -287,14 +287,28 @@ def build_task_canceled(task_id):
 @backend_ns.route("/pending-actions/")
 def pending_actions():
     'get the list of actions backand should take care of'
+    busy_namespaces = set()
     data = []
+    # waiting repos are ordered
     for action in actions_logic.ActionsLogic.get_waiting():
+        if (
+            action.object_type == "copr"
+            and action.action_type == ActionTypeEnum("delete")
+        ):
+            busy_namespaces.add(action.copr.full_name)
+        elif action.copr.full_name in busy_namespaces:
+            # e.g. copr delete _ && copr fork _; will cause race condition
+            # so don't process new action with the same namespace until delete
+            # action is processed
+            # https://github.com/fedora-copr/copr/issues/2698
+            continue
+
         data.append({
             'id': action.id,
             'priority': action.priority or action.default_priority,
         })
-    return flask.json.dumps(data)
 
+    return flask.json.dumps(data)
 
 
 @backend_ns.route("/action/<int:action_id>/")