Tagging.remove_unused_tags should gracefully handle already deleted tags

CHANGELOG.md

@@ -14,6 +14,7 @@ As such, _Breaking Changes_ are major. _Features_ would map to either major or m
 
 * Fixes
   * [@nbulaj Add support for Ruby 2.7 and it's kwargs](https://github.com/mbleigh/acts-as-taggable-on/pull/910)  
+  * [@irphilli Tagging.remove_unused_tags should gracefully handle already deleted tags](https://github.com/mbleigh/acts-as-taggable-on/pull/988)
 
 ### [6.5.0 / 2019-11-07](https://github.com/mbleigh/acts-as-taggable-on/compare/v6.0.0...v6.5.0)
 

lib/acts_as_taggable_on/tagging.rb

@@ -24,13 +24,15 @@ class Tagging < ::ActiveRecord::Base #:nodoc:
     private
 
     def remove_unused_tags
-      if ActsAsTaggableOn.remove_unused_tags
-        if ActsAsTaggableOn.tags_counter
-          tag.destroy if tag.reload.taggings_count.zero?
-        else
-          tag.destroy if tag.reload.taggings.count.zero?
-        end
+      return if !ActsAsTaggableOn.remove_unused_tags || tag.blank?
+
+      if ActsAsTaggableOn.tags_counter
+        tag.destroy if tag.reload.taggings_count.zero?
+      else
+        tag.destroy if tag.reload.taggings.count.zero?
       end
+    rescue ActiveRecord::RecordNotFound
+      # Tag already deleted - nothing else to do
     end
   end
 end

spec/acts_as_taggable_on/tagging_spec.rb

@@ -49,6 +49,26 @@
     ActsAsTaggableOn.remove_unused_tags = previous_setting
   end
 
+  it 'should succesfully destroy taggings if tag already destroyed' do
+    previous_setting = ActsAsTaggableOn.remove_unused_tags
+    ActsAsTaggableOn.remove_unused_tags = true
+    ActsAsTaggableOn::Tag.destroy_all
+    expect(ActsAsTaggableOn::Tagging.count).to eql(0)
+    @taggable = TaggableModel.create(name: 'Bob Jones')
+    @taggable.update_attribute :tag_list, 'aaa,bbb,ccc'
+
+    # Initalize taggings with preloaded tags
+    taggings = ActsAsTaggableOn::Tagging.preload(:tag).all
+    taggings.to_a
+
+    # Delete tags before destroying taggings
+    ActsAsTaggableOn::Tag.delete_all
+    taggings.destroy_all
+
+    expect(ActsAsTaggableOn::Tagging.count).to eql(0)
+    ActsAsTaggableOn.remove_unused_tags = previous_setting
+  end
+
   describe 'context scopes' do
     before do
       @tagging_2 = ActsAsTaggableOn::Tagging.new