`default_value` and explicit null/nil

[lowip]

Environment

• Elixir version:

Erlang/OTP 21 [erts-10.2.1] [source] [64-bit] [smp:8:8] [ds:8:8:10] [async-threads:1] [hipe] [dtrace]
Elixir 1.7.4 (compiled with Erlang/OTP 21)

• Absinthe version (mix deps | grep absinthe):

* absinthe 1.4.13 (Hex package) (mix)
  locked at 1.4.13 (absinthe) 81eb2ff4

• Client Framework and version (Relay, Apollo, etc): NA

Expected behavior

With the following input_object:

input_object :comment_filter do
  field :user_id, :id
  field :post_id, :id
  field :parent_id, :id, default_value: nil
end

used in the connection field:

connection field :comments, node_type: :comment do
  arg :filter, non_null(:comment_filter)
  middleware ParseIDs, filter: [user_id: :user, post_id: :post, parent_id: :comment]
  resolve &Resolvers.Core.comments/2
end

called with the query:

{
  comments(first: 1, filter: {postId: "POST_ID"}) {
    edges { cursor }
  }
}

I expect my resolver &Resolvers.Core.comments/2 to be called with the following args:

def comments(args, _res) do
  IO.inspect args
  # %{filter: %{parent_id: nil, post_id: "POST_ID"}, first: 1}
  ...
end

Actual behavior

Instead my args are missing the nil default value for :parent_id:

def comments(args, _res) do
  IO.inspect args
  # %{filter: %{post_id: "POST_ID"}, first: 1}
  ...
end

There is currently no way to represent an explicit null/nil value using the default_value option.

According to graphql-js, when setting null as the default value, it should be taken into account:

• https://git.io/fhTT0
• https://git.io/fhTTB

Let me know if this is the expected behaviour for Absinthe, if so I will close the issue.

[pmargreff]

I'm working on it.

[pmargreff]

Looking into GraphQL language definitions: DefaultValue can be any Value[Const], while NullValue is a Value[Const], so your suggestion makes sense.

The problem is, taking a brief look into the internals and seems like nil value is coupled with value absence. I'll try a POC replacing it with a %None{} or something like that.

Suggestions are welcome.

[pmargreff]

Put it on hold, to much work on internals for my knowledge level, will work on easier ones first ...

[binaryseed]

@benwilson512 Is default_value: nil something that should be supported?

[pmargreff]

@binaryseed @benwilson512 this feature is implemented in pmargreff/absinthe/feature/allow-nil-as-default, I'm just awaiting the merge of #940 first.

In the first PR, I did the necessary refactor to allow the default_value: nil implementation in a simple way. The branch not submitted already has this feature.

[sraka1]

@pmargreff are you still working on this?

[pmargreff]

@sraka1 Nope. I have implemented the feature, and put that in a queue to be merged after a refactor. Once the refactor had no response (I closed it after a while) I have never merged the feature itself (both are ref at #656 (comment)).

But it should work flawlessly, as far you rebase pmargreff/absinthe/feature/allow-nil-as-default from the current master does not conflict or have any regressions. The new specs at mentioned branch should suffice the intended behavior. Feel free to open a PR and keep going from that point.

[benzene73]

It's still not done. Can't pass in null as default values.