Implement detection for sti for including subclasses in check

lib/cancan/class_matcher.rb

@@ -1,3 +1,5 @@
+require_relative 'sti_detector'
+
 # This class is responsible for matching classes and their subclasses as well as
 # upmatching classes to their ancestors.
 # This is used to generate sti connections
@@ -12,6 +14,8 @@ def self.matches_subject_class?(subjects, subject)
   def self.matching_class_check(subject, sub, has_subclasses)
     matches = matches_class_or_is_related(subject, sub)
     if has_subclasses
+      return matches unless StiDetector.sti_class?(sub)
+
       matches || subject.subclasses.include?(sub)
     else
       matches

lib/cancan/model_adapters/sti_normalizer.rb

@@ -1,3 +1,5 @@
+require_relative '../sti_detector'
+
 # this class is responsible for detecting sti classes and creating new rules for the
 # relevant subclasses, using the inheritance_column as a merger
 module CanCan
@@ -20,9 +22,7 @@ def normalize(rules)
         private
 
         def update_rule(subject, rule, rules_cache)
-          return false unless subject.respond_to?(:descends_from_active_record?)
-          return false if subject == :all || subject.descends_from_active_record?
-          return false unless subject < ActiveRecord::Base
+          return false unless StiDetector.sti_class?(subject)
 
           rules_cache.push(build_rule_for_subclass(rule, subject))
           true
@@ -31,7 +31,7 @@ def update_rule(subject, rule, rules_cache)
         # create a new rule for the subclasses that links on the inheritance_column
         def build_rule_for_subclass(rule, subject)
           CanCan::Rule.new(rule.base_behavior, rule.actions, subject.superclass,
-                           rule.conditions.merge(subject.inheritance_column => subject.name), rule.block)
+                           rule.conditions.merge(subject.inheritance_column => subject.sti_name), rule.block)
         end
       end
     end

lib/cancan/sti_detector.rb

@@ -0,0 +1,12 @@
+# frozen_string_literal: true
+
+class StiDetector
+  def self.sti_class?(subject)
+    return false unless defined?(ActiveRecord::Base)
+    return false unless subject.respond_to?(:descends_from_active_record?)
+    return false if subject == :all || subject.descends_from_active_record?
+    return false unless subject < ActiveRecord::Base
+
+    true
+  end
+end

spec/cancan/model_adapters/active_record_adapter_spec.rb

@@ -1033,6 +1033,35 @@ class JsonTransaction < ActiveRecord::Base
     end
   end
 
+  context 'with rule application to subclass for non sti class' do
+    before do
+      ActiveRecord::Schema.define do
+        create_table :parents, force: true
+
+        create_table :children, force: true
+      end
+
+      class ApplicationRecord < ActiveRecord::Base
+        self.abstract_class = true
+      end
+
+      class Parent < ActiveRecord::Base
+      end
+
+      class Child < Parent
+      end
+    end
+
+    it 'rules are not effecting parent class' do
+      u1 = User.create!(name: 'pippo')
+      ability = Ability.new(u1)
+      ability.can :manage, Parent
+      ability.cannot :manage, Child
+      expect(ability).not_to be_able_to(:index, Child)
+      expect(ability).to be_able_to(:index, Parent)
+    end
+  end
+
   context 'when STI is in use' do
     before do
       ActiveRecord::Schema.define do