Fixes #3942 - New online notifications blocks data privacy user deletion.

app/models/data_privacy_task.rb

@@ -25,19 +25,38 @@ class DataPrivacyTask < ApplicationModel
     handle_exception(e)
   end
 
+  # set user inactive before destroy to prevent
+  # new online notifications or other events while
+  # the deletion process is running
+  # https://github.com/zammad/zammad/issues/3942
+  def update_inactive(object)
+    object.update(active: false)
+  end
+
   def perform_deletable
-    return if deletable.blank?
+    return if !deletable_type.constantize.exists?(id: deletable_id)
 
     prepare_deletion_preview
     save!
 
     if delete_organization?
-      deletable.organization.destroy(associations: true)
+      perform_organization
     else
-      deletable.destroy
+      perform_user
     end
   end
 
+  def perform_organization
+    update_inactive(deletable.organization)
+    deletable.organization.members.find_each { |user| update_inactive(user) }
+    deletable.organization.destroy(associations: true)
+  end
+
+  def perform_user
+    update_inactive(deletable)
+    deletable.destroy
+  end
+
   def handle_exception(e)
     Rails.logger.error e
     preferences[:error] = "ERROR: #{e.inspect}"

spec/models/data_privacy_task_spec.rb

@@ -36,18 +36,11 @@ RSpec.describe DataPrivacyTask, type: :model do
       expect(create(:data_privacy_task, deletable: admin)).to be_truthy
     end
 
-    it 'sets the failed state when task failed' do
+    it 'sets no error message when user is already deleted' do
       task = create(:data_privacy_task, deletable: user)
       user.destroy
       task.perform
-      expect(task.reload.state).to eq('failed')
-    end
-
-    it 'sets an error message when task failed' do
-      task = create(:data_privacy_task, deletable: user)
-      user.destroy
-      task.perform
-      expect(task.reload.preferences[:error]).to eq("ERROR: #<ActiveRecord::RecordNotFound: Couldn't find User with 'id'=#{user.id}>")
+      expect(task.reload.state).to eq('completed')
     end
   end