From d5bf649a535948e70692e521ce3070595334e71b Mon Sep 17 00:00:00 2001
From: Seb Jacobs <me@sebjacobs.com>
Date: Thu, 15 Jan 2015 23:03:23 +0000
Subject: Add support for bidirectional destroy dependencies

Prior to this commit if you defined a bidirectional relationship
between two models with destroy dependencies on both sides, a call to
`destroy` would result in an infinite callback loop.

Take the following relationship.

    class Content < ActiveRecord::Base
      has_one :content_position, dependent: :destroy
    end

    class ContentPosition < ActiveRecord::Base
      belongs_to :content, dependent: :destroy
    end

Calling `Content#destroy` or `ContentPosition#destroy` would result in
an infinite callback loop.

This commit changes the behaviour of `ActiveRecord::Callbacks#destroy`
so that it guards against subsequent callbacks.

Thanks to @zetter for demonstrating the issue with failing tests[1].

[1] rails#13609
---
 activerecord/test/models/content.rb | 40 +++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)
 create mode 100644 activerecord/test/models/content.rb

(limited to 'activerecord/test/models/content.rb')

diff --git a/activerecord/test/models/content.rb b/activerecord/test/models/content.rb
new file mode 100644
index 0000000000..140e1dfc78
--- /dev/null
+++ b/activerecord/test/models/content.rb
@@ -0,0 +1,40 @@
+class Content < ActiveRecord::Base
+  self.table_name = 'content'
+  has_one :content_position, dependent: :destroy
+
+  def self.destroyed_ids
+    @destroyed_ids ||= []
+  end
+
+  before_destroy do |object|
+    Content.destroyed_ids << object.id
+  end
+end
+
+class ContentWhichRequiresTwoDestroyCalls < ActiveRecord::Base
+  self.table_name = 'content'
+  has_one :content_position, foreign_key: 'content_id', dependent: :destroy
+
+  after_initialize do
+    @destroy_count = 0
+  end
+
+  before_destroy do
+    @destroy_count += 1
+    if @destroy_count == 1
+      throw :abort
+    end
+  end
+end
+
+class ContentPosition < ActiveRecord::Base
+  belongs_to :content, dependent: :destroy
+
+  def self.destroyed_ids
+    @destroyed_ids ||= []
+  end
+
+  before_destroy do |object|
+    ContentPosition.destroyed_ids << object.id
+  end
+end
-- 
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