When tag is deleted, remove it also from group's managed filter

https://bugzilla.redhat.com/show_bug.cgi?id=1300809

app/models/miq_group.rb

@@ -142,6 +142,26 @@ def set_filters(type, filter)
     self.filters[type.to_s] = filter
   end
 
+  def self.remove_tag_from_all_managed_filters(tag)
+    all.each do |miq_group|
+      miq_group.remove_tag_from_managed_filter(tag)
+      miq_group.save if miq_group.filters_changed?
+    end
+  end
+
+  def remove_tag_from_managed_filter(filter_to_remove)
+    if get_managed_filters.present?
+      *category, _tag = filter_to_remove.split("/")
+      category = category.join("/")
+      self.filters["managed"].each do |filter|
+        next unless filter.first.starts_with?(category)
+        next unless filter.include?(filter_to_remove)
+        filter.delete(filter_to_remove)
+      end
+      self.filters["managed"].reject!(&:empty?)
+    end
+  end
+
   def set_managed_filters(filter)
     set_filters("managed", filter)
   end

app/models/tag.rb

@@ -4,6 +4,8 @@ class Tag < ApplicationRecord
   virtual_has_one :category,       :class_name => "Classification"
   virtual_has_one :categorization, :class_name => "Hash"
 
+  before_destroy :remove_from_managed_filters
+
   def self.to_tag(name, options = {})
     File.join(Tag.get_namespace(options), name)
   end
@@ -143,6 +145,10 @@ def categorization
 
   private
 
+  def remove_from_managed_filters
+    MiqGroup.remove_tag_from_all_managed_filters(name)
+  end
+
   def name_path
     @name_path ||= name.sub(%r{^/[^/]*/}, "")
   end