FIX: verify filtered tags when checking for category minimum required tags

lib/discourse_tagging.rb

@@ -29,12 +29,6 @@ module DiscourseTagging
       category = topic.category
       tag_names = tag_names + old_tag_names if append
 
-      # validate minimum required tags for a category
-      if !guardian.is_staff? && category && category.minimum_required_tags > 0 && tag_names.length < category.minimum_required_tags
-        topic.errors[:base] << I18n.t("tags.minimum_required_tags", count: category.minimum_required_tags)
-        return false
-      end
-
       if tag_names.present?
         # guardian is explicitly nil cause we don't want to strip all
         # staff tags that already passed validation
@@ -54,8 +48,20 @@ module DiscourseTagging
           end
         end
 
+        # validate minimum required tags for a category
+        if !guardian.is_staff? && category && category.minimum_required_tags > 0 && tags.length < category.minimum_required_tags
+          topic.errors[:base] << I18n.t("tags.minimum_required_tags", count: category.minimum_required_tags)
+          return false
+        end
+
         topic.tags = tags
       else
+        # validate minimum required tags for a category
+        if !guardian.is_staff? && category && category.minimum_required_tags > 0
+          topic.errors[:base] << I18n.t("tags.minimum_required_tags", count: category.minimum_required_tags)
+          return false
+        end
+
         topic.tags = []
       end
       topic.tags_changed = true

spec/components/discourse_tagging_spec.rb

@@ -101,6 +101,12 @@ describe DiscourseTagging do
       let(:category) { Fabricate(:category, minimum_required_tags: 2) }
       let(:topic) { Fabricate(:topic, category: category) }
 
+      it 'when tags are not present' do
+        valid = DiscourseTagging.tag_topic_by_names(topic, Guardian.new(user), [])
+        expect(valid).to eq(false)
+        expect(topic.errors[:base]&.first).to eq(I18n.t("tags.minimum_required_tags", count: category.minimum_required_tags))
+      end
+
       it 'when tags are less than minimum_required_tags' do
         valid = DiscourseTagging.tag_topic_by_names(topic, Guardian.new(user), [tag1.name])
         expect(valid).to eq(false)