FIX: scope memoization of category moderation per category (#17786)

lib/guardian.rb

@@ -112,8 +112,8 @@ class Guardian
   def is_category_group_moderator?(category)
     return false unless category
     return false unless authenticated?
-
-    @is_category_group_moderator ||= begin
+    @is_category_group_moderator ||= {}
+    @is_category_group_moderator[category.id] ||= begin
       SiteSetting.enable_category_group_moderation? &&
         category.present? &&
         category.reviewable_by_group_id.present? &&

spec/lib/guardian_spec.rb

@@ -3953,4 +3953,21 @@ RSpec.describe Guardian do
       expect(admin.guardian.can_mention_here?).to eq(true)
     end
   end
+
+  describe "#is_category_group_moderator" do
+    before do
+      SiteSetting.enable_category_group_moderation = true
+    end
+
+    fab!(:category) { Fabricate(:category) }
+
+    it "should correctly detect category moderation" do
+      group.add(user)
+      category.reviewable_by_group_id = group.id
+      guardian = Guardian.new(user)
+
+      expect(guardian.is_category_group_moderator?(category)).to eq(true)
+      expect(guardian.is_category_group_moderator?(plain_category)).to eq(false)
+    end
+  end
 end