Infinite loop in circular associations

[heartsentwined]

active_model_serializers can handle self-referencing associations fine, e.g. categories, but it will run into an infinite loop if you try to sideload circular associations. An example is the twitter-esque follower-followed association pair.

class BaseSerializer < ActiveModel::Serializer
  embed :ids, include: true
end

class FollowerSerializer < BaseSerializer
  has_many :followeds
end

class FollowedSerializer < BaseSerializer
  has_many :followers
end

Let's say you start by requesting a follower. active_model_serializers will traverse its followeds, sideload the followed models by initiating a new FollowedSerializer for each, and if any followed points back to the original follower via its own has_many :followers association, we have an infinite loop.

The current workaround is, unfortunately, disable sideloading entirely for the offending associations.

class BaseSerializer < ActiveModel::Serializer
  embed :ids, include: true
end

class FollowerSerializer < BaseSerializer
  has_many :followeds, embed: :ids, include: false
end

class FollowedSerializer < BaseSerializer
  has_many :followers, embed: :ids, include: false
end

Perhaps keeping track of the model + primary key while loading associations (recursively) can solve this issue? This way the same model will only be serialized once.

[darthdeus]

Funny, I ran into this exact issue about 2 hours ago, using the same exact follower/following structure :)

[heartsentwined]

Can I +1 myself? :-)

[samuil]

It seems that as of 0.7.0 this issue is not anymore present.

[steveklabnik]

Thanks!

[heartsentwined]

Confirmation: it has indeed been fixed in 0.7.0. Kudos to whoever that patched the issue!

[codezomb]

This is still an issue, the following results in a stack level too deep error. This is using version 0.7.0.

target_serializer.rb

class TargetSerializer < ActiveModel::Serializer
  attributes :email, :first_name, :last_name
  has_many :lists
end

list_serializer.rb

class ListSerializer < ActiveModel::Serializer
  attributes :name
  has_many :targets
end

[steveklabnik]

@gitt Can you try against master, please? I plan on releasing over the weekend.

[codezomb]

I will see what i can do tonight or tomorrow.

Sent from my iPhone

On May 2, 2013, at 6:32 PM, Steve Klabnik notifications@github.com wrote:

@gitt Can you try against master, please? I plan on releasing over the weekend.

—
Reply to this email directly or view it on GitHub.

[steveklabnik]

Thanks. <3

[codezomb]

@steveklabnik Same response stack level too deep.

SystemStackError - stack level too deep:
(gem) actionpack-3.2.13/lib/action_dispatch/middleware/reloader.rb:70:in `'

65       response = @app.call(env)
66       response[2] = ActionDispatch::BodyProxy.new(response[2]) { cleanup! }
67       response
68     rescue Exception
69       cleanup!
70       raise
71     end
72 
73     def prepare! #:nodoc:
74       run_callbacks :prepare if validated?
75     end

[codezomb]

Just tested with embded: :ids, include: false. This works. Without include: false, it fails.

class ListSerializer < ActiveModel::Serializer
  attributes :name
  has_many :targets, :children, embed: :ids, include: false
end

class TargetSerializer < ActiveModel::Serializer
  attributes :email, :first_name, :last_name
  has_many :lists, embed: :ids, include: false
end

[steveklabnik]

Word, thanks. I'll try to look into it...