Support JSON serialize

[yhirano55]

If it use active hash with web api responses, as_json behavior is different between active hash's instance and active model's instance.

  1) ActiveHash Base #as_json returns a hash
     Failure/Error: expect(country.as_json).to eq({"id" => 1, "name" => "US", "language" => "English"})

       expected: {"id"=>1, "name"=>"US", "language"=>"English"}
            got: {"attributes"=>{"id"=>1, "name"=>"US", "language"=>"English"}}

We don't need attributes route key.

If it includes ActiveModel::Serializers::JSON, behavior of active hash's instance would be as same as a behavior active model's instance.

Thanks :)

---

The reason to need this change

• When we implement web api with using active hash model and active model serializers gem, we need include ActiveModel::Serializers::JSON module to all active hash's models.
• It's not a little convenient for us. So I've opened this pull request.

[yhirano55]

Rails 6.0 or later returns stringified keys hash, but Rails 5.2 or earlier returns symbolized keys hash. So I used stringify_keys method.

[pfeiffer]

This PR doesn't solve the underlying issue; namely that attributes return a hash with the keys as symbols, while ActiveModel::Serializer explicitly mentions that it expect keys to be strings (docs).

Even with this PR, the as_json doesn't work as expected:

Country.find(1).as_json
=> { id: 1, name: "US", .. }

Country.find(1).as_json(only: [:name])
=> {} # Huh!?

[yhirano55]

@pfeiffer Thanks for the comment. Let me check it.

[yhirano55]

ActiveHash's attributes are converted to symbolized keys in its constructor.

But in ActiveModel::Serialization#serializable_hash, it compares stringified keys and symbolised keys, so it seems it doesn't work only and except options.

https://github.com/zilkey/active_hash/blob/d2ccb223256b876a69b217ec70f314bdf71d2573/lib/active_hash/base.rb#L404-L411

ActiveModel::Serialization:

https://github.com/rails/rails/blob/ac65e560db598c7a8b1b6aaea1e5656ff3b27f08/activemodel/lib/active_model/serialization.rb#L123-L131

I consider a better solution. If you have an idea, let me know how resolve it. Thanks.

[pfeiffer]

I think way to solve this is to migrate to having keys as strings in the attributes attribute. This is also how ActiveModel::Attributes and ActiveRecord behaves, and will allow full compatibility with ActiveModel mixins such as AM::Serialization etc.

# ActiveRecord
class User < ApplicationRecord; end

User.find(1).attributes
# => { "id" => 1, "name": "John", ... }

# ActiveModel
class Product
  include ActiveModel::Attributes

  attribute :sku, :string
end

Product.new(sku: "red_shirt").attributes
# => { "sku": "red_shirt" }

It's however a breaking change, since the keys of @attributes are currently forced to be symbols. Personally, I think having keys as strings is the way to go.

If needed, a potential migration path would be to store keys as strings with stringify_keys!, but still allow access to the attributes via symbol, but with a deprecation warning before dropping support for symbols as key in next major version, but this would probably require that @zilkey signs off on this migration plan.

What do you and @zilkey think?

[zilkey]

What about sort of a parallel track?

• we push a version (maybe 3.1.1?) that deprecates symbol keys, but maintains 100% compatibility (still has symbols / still has attributes)
• we push a new version 4.0.0 that makes all the breaking changes:
  • stores attributes as strings
  • returns attributes as strings
  • removes the attributes key from as_json

We'd created a 3.x.x branch here, and can release changes on both for a little while. Any reason to not do this?

[pfeiffer]

What about sort of a parallel track?

Sounds like a great plan! Happy to contribute if needed :-)

[kbrock]

Looking back over this.

I think you can manually add this to each of your models to gain this functionality.

include ActiveModel::Serializers::JSON

Looks like this lost steam. I'm not sure if there is desire to get this in and beak compatibility.

[kbrock]

kicking this build

[pfeiffer]

Looking back over this.

I think you can manually add this to each of your models to gain this functionality.

include ActiveModel::Serializers::JSON

Looks like this lost steam. I'm not sure if there is desire to get this in and beak compatibility.

No the issue would still be here. The issue is that ActiveHash stores the attributes with symbols as keys, causing :only and :except options passed to as_json to not work, as it compares strings to symbols.

[kbrock]

@pfeiffer ugh. you had already clearly stated the problem. sorry about that.

Are the 2 branches going to be that much different?
Do you think it will be possibly to backport the same PRs to both branches while 2 live in parallel?

[kbrock]

@pfeiffer Sorry for lag on this one. (going over unresolved PRs)

So if we want this fixed we need to break compatibility and store strings as keys?
We just merged #312 which made sure all attributes were consistent - symbols for now, which seemed to be the way it was expected to work.

But looking at #310, it seems like at least to_json and column_names wants String names.

Just thinking out loud:

And visiting the source for as_json, it almost feels like we want to alias field to attribute and rearrange our internals to leverage attributes