Redmine

Since the priority_id column of the issues table has a NOT NULL constraint, it should be prohibited to disable all issue priorities.

It can be fixed by updating issue.rb like this:

diff --git a/app/models/issue_priority.rb b/app/models/issue_priority.rb
index 6cc75b904..a92da9140 100644
--- a/app/models/issue_priority.rb
+++ b/app/models/issue_priority.rb
@@ -20,6 +20,8 @@
 class IssuePriority < Enumeration
   has_many :issues, :foreign_key => 'priority_id'

+  validate :at_least_one_active, if: :active_changed?
+
   after_destroy {|priority| priority.class.compute_position_names}
   after_save do |priority|
     if (priority.saved_change_to_position? && priority.position) ||
@@ -88,4 +90,13 @@ class IssuePriority < Enumeration
       end
     end
   end
+
+  private
+
+  def at_least_one_active
+    # Check if this record is inactive and no other active records exist
+    if !active && IssuePriority.where(active: true).where.not(id: self.id).none?
+      errors.add(:base, "At least one IssuePriority must be active.")
+    end
+  end
 end