Use metadata to return additional information

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1

Hi there!

I’m using ash_json_api and I’m trying to add metadata to the response of a create action, but it doesn’t seem to be included in the meta field. I’ve got the following relevant pieces in my resource:

  json_api do
    type "asset"

    routes do
      base "/assets"
      get :read
      index :read
      post :create
    end
  end

  actions do
    defaults [:read]

    create :create do
      # Set the current user as the owner of the asset
      change relate_actor(:user)
      # Create signed url for the asset
      metadata :signed_url, :string, allow_nil?: false
      change Swoop.Media.Changes.GeneratePresignedUrl
    end
  end

In GeneratePresignedUrl I’m returning this in a after_action function:

        result = Ash.Resource.put_metadata(result, :signed_url, url)
        {:ok, result}

But unfortunately after doing a POST to the endpoint with curl, I’m getting empty meta fields:

{"data":{"attributes":{},"id":"11700f40-c37b-4776-b3b0-7d1207cbb6d0","links":{},"meta":{},"relationships":{},"type":"asset"},"jsonapi":{"version":"1.0"},"links":{"self":"http://localhost:4000/api/json/assets"},"meta":{}}

What am I missing?

Thanks in advance!

2

At the moment, action metadata isn’t translated to record meta in the JSON:API. Please open a feature request for this :slight_smile:

To accomplish what you want, you have two options:

  1. you can use the metadata option on the route to add route-level meta. This is done via a function of the various components of the request. This will be in the top level meta, not the record’s metadata. DSL: AshJsonApi.Resource — ash_json_api v1.4.9

  2. you can use a calculation instead of metadata:

calculate :signed_url, :string, fn records -> 
  Enum.map(records, fn record -> 
    signed_url(record)
  end)
end

This can then be requested in the fields parameter, i.e fields[type-name]=foo,bar,baz,signed_url.

3

Great, thanks! I’ll use one of those options for now and open a feature request.

Just out of curiosity, what is the metadata option on the actions used for?

4

Actually kept my code the same, but changed my create route to:

      post :create do
        metadata fn subject, result, request ->
          %{signed_url: result.__metadata__.signed_url}
        end
      end

So that I possibly can reuse the metadata in other places than the route. But still curious to know if there may be other use cases :slight_smile:

5

The way you are attempting to use it is actually its intended use case :slight_smile: However, it just hasn’t been hooked up to ash_json_api yet. AshGraphql has a way to expose metadata in exactly that same way. It requires some adjustments to our open api schema generation logic, because we need to do one of three things:

  1. allow you to configure a special type name for the results of the action, i.e asset-with-url
  2. we have to add that meta to all types
  3. we have to keep meta as untyped “object”

Its a solvable problem, just hasn’t been implemented yet :slight_smile:

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