Sideload root only

[ahawkins]

Give an option to include associations from the initializer serializer only. This is good when you need to serializer many objects that are all related, but don't want to include the entire graph.

I wonder if this should be on by default. All serializers sideloading everything is path for serious performance problems.

[coveralls]

Coverage increased (+0%) when pulling da1928b on ahawkins:sideload-root-only into 8ac4bf9 on rails-api:master.

[rwjblue]

I agree with @ahawkins that we should consider this as a more sane default than to load and serialize everything.

The test case that was added makes the reasoning pretty clear. Here is a simple recap using this gist (basically just user has many posts):

# With this PR and using the include_root_only: true flag the output is:
    {
      post: { id: 1, title: 'Post 1', author_id: 1 },
      authors: [{ id: 1, name: 'Adam Hawkins', post_ids: [1,2] }]
    }

# Without this PR the output is:

    {
      :post=>{:id=>1, :title=>"Post 1", :author_id=>1},
      :authors=>[{:id=>1, :name=>"Robert Jackson", :post_ids=>[1, 2]}], 
      :posts=>[{:id=>1, :title=>"Post 1", :author_id=>1}, {:id=>2, :title=>"Post 2", :author_id=>1}]
    }

[ahawkins]

@steveklabnik ping

[steveklabnik]

I'm awaiting @spastorino 's stuff to land before merging anything.

[mixonic]

I'd even suggest this should be the default behavior.

[shekibobo]

👍 for default behavior. Thoughts on :shallow_associations for the option name?

[teeparham]

The way I've handled this is to define 2 serializers for each resource. I end up with one serializer used for index that specifies shallow loads, & one for show that does a deep load. I typically have 2 serializers for each resource, and specify which is used in various situations.

For example, I have a MonkeySerialzer and a DeepMonkeySerializer. My controllers often look like this:

def index
  render json: monkeys
end

def show
  render json: monkey, serializer: DeepMonkeySerializer
end

[spastorino]

We are going to implement contexts for Serializers that also will help solving this issue so I'm closing this for now.
Thanks guys! ❤️