Minimum reproduction repository for the "could not infer polymorphic embed from data" issue with polymorphic_embed library.

Following the polymorphic_embed's usage example, making any requests (see reproduction steps) results in the following error:

• could not infer polymorphic embed from data %{<embedded-data>}

Note: Using Docker Compose for easier setup and reproduction; should be also replicable without its utilization and shouldn't affect the functionality of the library.

The repository has been set up by following steps below:

1. Initialize the Phoenix project:

   mix phx.new pedemo
   

2. Create the necessary Docker/Docker Compose configuration:

   • Create Dockerfile
   • Create docker-compose.yml
   • Update .gitignore
   • Update config/dev.exs

3. Add the polymorphic_embed dependency into mix.esx.

4. Start up the application stack:

   docker-compose up --build -d
   

5. Find the Phoenix container and attach to its CLI:

   docker ps
   docker exec -it <container-id> /bin/sh
   

6. Generate the example Reminder resource and run the migration:

   mix phx.gen.json Reminders Reminder reminders date:utc_datetime text:string channel:map
   mix ecto.migrate
   exit
   

7. Add the resource into the router under the API scope in lib/pedemo_web/router.ex:

   resources "/reminders", ReminderController, except: [:new, :edit]
   

8. Update the Reminders resource using the polymorphic_embed example in lib/pedemo/reminders/reminder.ex:

   defmodule Pedemo.Reminders.Reminder do
     use Ecto.Schema
     import Ecto.Changeset
     import PolymorphicEmbed
   
     schema "reminders" do
       field :date, :utc_datetime
       field :text, :string
   
       polymorphic_embeds_one(:channel,
         types: [
           sms: Pedemo.Channel.SMS,
           email: Pedemo.Channel.Email
         ],
         on_type_not_found: :raise,
         on_replace: :update
       )
   
       timestamps()
     end
   
     @doc false
     def changeset(reminder, attrs) do
       reminder
       |> cast(attrs, [:date, :text])
       |> cast_polymorphic_embed(:channel, required: true)
       |> validate_required([:date, :text])
     end
   end

9. Add example modules for the embedded schemas in lib/pedemo/channels/channel.ex:

   defmodule Pedemo.Channel.Email do
     use Ecto.Schema
     import Ecto.Changeset
   
     @primary_key false
   
     embedded_schema do
       field :address, :string
       field :confirmed, :boolean
     end
   
     def changeset(email, params) do
       email
       |> cast(params, ~w(address confirmed)a)
       |> validate_required(:address)
       |> validate_length(:address, min: 4)
     end
   end
   
   defmodule Pedemo.Channel.SMS do
     use Ecto.Schema
   
     @primary_key false
   
     embedded_schema do
       field :number, :string
     end
   end

1. Start up the application stack:

   docker-compose up --build -d
   

2. If not done previously, run the Reminders resource migration - follow steps 5 and 6 from the Initial setup section.
3. Make a POST request to the example endpoint at localhost:4000/api/reminders, using any tool of your choice, with the one of following JSON payloads:

   {
     "reminder": {
       "date": "2022-09-06 11:04:19.240294+00",
       "text": "test text",
       "channel": {
         "number": "0123456789"
       }
     }
   }
   

   {
     "reminder": {
       "date": "2022-09-06 11:04:19.240294+00",
       "text": "test",
       "channel": {
         "address": "test address",
         "confirmed": true
       }
     }
   }