Fix #4199: Aliased tags not included in related wiki tags.

app/models/wiki_page.rb

@@ -220,7 +220,8 @@ class WikiPage < ApplicationRecord
   def tags
     titles = DText.parse_wiki_titles(body).uniq
     tags = Tag.nonempty.where(name: titles).pluck(:name)
-    titles & tags
+    tags += TagAlias.active.where(antecedent_name: titles).pluck(:antecedent_name)
+    TagAlias.to_aliased(titles & tags)
   end
 
   def visible?

test/unit/related_tag_query_test.rb

@@ -98,6 +98,14 @@ class RelatedTagQueryTest < ActiveSupport::TestCase
         query = RelatedTagQuery.new(query: "wiki")
         assert_equal(%w[ccc bbb aaa], query.wiki_page_tags)
       end
+
+      should "return aliased tags" do
+        create(:tag_alias, antecedent_name: "kitten", consequent_name: "cat", status: "active")
+        create(:wiki_page, title: "wiki", body: "[[kitten]]")
+
+        query = RelatedTagQuery.new(query: "wiki")
+        assert_equal(%w[cat], query.wiki_page_tags)
+      end
     end
   end