Fix SystemStackError with ActiveRecord

If you use the default `otp_counter` column name,
InstanceMethodsOnActivation#otp_counter calls `otp_counter` resulting in
a stack overflow.

active_model_otp.gemspec

@@ -21,7 +21,9 @@ Gem::Specification.new do |spec|
   spec.add_dependency "activemodel"
   spec.add_dependency "rotp"
 
+  spec.add_development_dependency "activerecord"
   spec.add_development_dependency "bundler", "~> 1.3"
   spec.add_development_dependency "rake"
   spec.add_development_dependency "minitest", "~> 5.4.2"
+  spec.add_development_dependency "sqlite3"
 end

lib/active_model/one_time_password.rb

@@ -96,11 +96,19 @@ def otp_column=(attr)
       end
 
       def otp_counter
-        self.public_send(self.class.otp_counter_column_name)
+        if self.class.otp_counter_column_name != 'otp_counter'
+          self.public_send(self.class.otp_counter_column_name)
+        else
+          super
+        end
       end
 
       def otp_counter=(attr)
-        self.public_send("#{self.class.otp_counter_column_name}=", attr)
+        if self.class.otp_counter_column_name != 'otp_counter'
+          self.public_send("#{self.class.otp_counter_column_name}=", attr)
+        else
+          super
+        end
       end
     end
   end

test/models/activerecord_user.rb

@@ -0,0 +1,3 @@
+class ActiverecordUser < ActiveRecord::Base
+  has_one_time_password counter_based: true
+end

test/one_time_password_test.rb

@@ -13,6 +13,10 @@ def setup
     @member = Member.new
     @member.email = nil
     @member.run_callbacks :create
+
+    @ar_user = ActiverecordUser.new
+    @ar_user.email = 'roberto@heapsource.com'
+    @ar_user.run_callbacks :create
   end
 
   def test_authenticate_with_otp
@@ -34,6 +38,17 @@ def test_counter_based_otp
     assert code != @member.otp_code(auto_increment: true)
   end
 
+  def test_counter_based_otp_active_record
+    code = @ar_user.otp_code
+    assert @ar_user.authenticate_otp(code)
+    assert @ar_user.authenticate_otp(code, auto_increment: true)
+    assert !@ar_user.authenticate_otp(code)
+    @ar_user.otp_counter -= 1
+    assert @ar_user.authenticate_otp(code)
+    assert code == @ar_user.otp_code
+    assert code != @ar_user.otp_code(auto_increment: true)
+  end
+
   def test_authenticate_with_otp_when_drift_is_allowed
     code = @user.otp_code(Time.now - 30)
     assert @user.authenticate_otp(code, drift: 60)

test/schema.rb

@@ -0,0 +1,12 @@
+ActiveRecord::Schema.define do
+  self.verbose = false
+
+  create_table :activerecord_users, :force => true do |t|
+    t.string :key
+    t.string :email
+    t.integer :otp_counter
+    t.string :otp_secret_key
+    t.timestamps
+  end
+
+end

test/test_helper.rb

@@ -8,5 +8,9 @@
 require "active_model_otp"
 require "minitest/autorun"
 require "minitest/unit"
+require "active_record"
+
+ActiveRecord::Base.establish_connection adapter: "sqlite3", database: ":memory:"
+load "#{ File.dirname(__FILE__) }/schema.rb"
 
 Dir["models/*.rb"].each {|file| require file }