From 759fcb65ee642d791d79c82293e108f3c635c94e Mon Sep 17 00:00:00 2001
From: Andy Klimczak <andyklimczak@fastmail.com>
Date: Sun, 10 Jun 2018 13:15:42 -0400
Subject: [PATCH] Fix `SystemStackError` when paranoid models have a circular
 `dependent: :destroy`

- Previously, paranoid models with a circular `dependent: :destroy` would recursively try to delete eachother
- Add a variable to check if the destroy callback has already been
called for that model
- Similar fix to rails/rails#18548
---
 lib/paranoia/active_record_5_2.rb |  6 ++++++
 test/paranoia_test.rb             | 28 ++++++++++++++++++++++++++--
 2 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/lib/paranoia/active_record_5_2.rb b/lib/paranoia/active_record_5_2.rb
index c9c5463f..f28202d5 100644
--- a/lib/paranoia/active_record_5_2.rb
+++ b/lib/paranoia/active_record_5_2.rb
@@ -4,6 +4,9 @@ def handle_dependency
 
     case options[:dependent]
     when :destroy
+      @_destroy_callback_already_called ||= false
+      return if @_destroy_callback_already_called
+      @_destroy_callback_already_called = true
       target.destroy
       if target.respond_to?(:paranoia_destroyed?)
         raise ActiveRecord::Rollback unless target.paranoia_destroyed?
@@ -23,7 +26,10 @@ def delete(method = options[:dependent])
       when :delete
         target.delete
       when :destroy
+        @_destroy_callback_already_called ||= false
+        return if @_destroy_callback_already_called
         target.destroyed_by_association = reflection
+        @_destroy_callback_already_called = true
         target.destroy
         if target.respond_to?(:paranoia_destroyed?)
           throw(:abort) unless target.paranoia_destroyed?
diff --git a/test/paranoia_test.rb b/test/paranoia_test.rb
index e08f9a7b..66f4c54f 100644
--- a/test/paranoia_test.rb
+++ b/test/paranoia_test.rb
@@ -46,8 +46,10 @@ def setup!
     'active_column_models' => 'deleted_at DATETIME, active BOOLEAN',
     'active_column_model_with_uniqueness_validations' => 'name VARCHAR(32), deleted_at DATETIME, active BOOLEAN',
     'paranoid_model_with_belongs_to_active_column_model_with_has_many_relationships' => 'name VARCHAR(32), deleted_at DATETIME, active BOOLEAN, active_column_model_with_has_many_relationship_id INTEGER',
-    'active_column_model_with_has_many_relationships' => 'name VARCHAR(32), deleted_at DATETIME, active BOOLEAN', 
-    'without_default_scope_models' => 'deleted_at DATETIME'
+    'active_column_model_with_has_many_relationships' => 'name VARCHAR(32), deleted_at DATETIME, active BOOLEAN',
+    'without_default_scope_models' => 'deleted_at DATETIME',
+    'paranoid_has_one_dependent_destroys' => 'deleted_at DATETIME',
+    'paranoid_belongs_to_dependent_destroys' => 'deleted_at DATETIME, paranoid_has_one_dependent_destroy_id INTEGER'
   }.each do |table_name, columns_as_sql_string|
     ActiveRecord::Base.connection.execute "CREATE TABLE #{table_name} (id INTEGER NOT NULL PRIMARY KEY, #{columns_as_sql_string})"
   end
@@ -1053,6 +1055,18 @@ def test_counter_cache_column_on_restore
       related_model.restore
       assert_equal 1, parent_model_with_counter_cache_column.reload.related_models_count
     end
+
+    def test_circular_dependent_destroy_has_one_belongs_to
+      has_one_dependent_destroy = ParanoidHasOneDependentDestroy.create
+      belongs_to_dependent_destroy = ParanoidBelongsToDependentDestroy.create
+      belongs_to_dependent_destroy.paranoid_has_one_dependent_destroy = has_one_dependent_destroy
+      belongs_to_dependent_destroy.save!
+
+      belongs_to_dependent_destroy.destroy
+
+      assert_equal false, has_one_dependent_destroy.reload.deleted_at.nil?
+      assert_equal false, belongs_to_dependent_destroy.reload.deleted_at.nil?
+    end
   end
 
   private
@@ -1356,6 +1370,16 @@ class PolymorphicModel < ActiveRecord::Base
   belongs_to :parent, polymorphic: true
 end
 
+class ParanoidHasOneDependentDestroy < ActiveRecord::Base
+  acts_as_paranoid
+  has_one :paranoid_belongs_to_dependent_destroy, dependent: :destroy
+end
+
+class ParanoidBelongsToDependentDestroy < ActiveRecord::Base
+  acts_as_paranoid
+  belongs_to :paranoid_has_one_dependent_destroy, dependent: :destroy
+end
+
 module Namespaced
   def self.table_name_prefix
     "namespaced_"