Decoding parameterized field error on schema load

[rauan]

• Elixir 1.12.3
• OTP 24
• Ecto 3.6/3.7

When loading a schema that contains a parameterized field like Ecto.Enum, the Ecto.Enum type loader cannot load the field because it is already decoded as the type that it is expecting:

 ** (ArgumentError) cannot load `:bar` as type {:parameterized, Ecto.Enum, %{on_dump: %{bar: "bar", foo: "foo"}, on_load: %{"bar" => :bar, "foo" => :foo}, type: :string, values: [:foo, :bar]}} for field :type in %Ecto.Adapters.DynamoDB.TestSchema.Person{__meta__: #Ecto.Schema.Metadata<:loaded, "test_person">, addresses: [], age: nil, country: nil, email: nil, first_name: nil, id: nil, inserted_at: nil, last_name: nil, nil_to_tags: nil, tags_to_tags: nil, type: nil, updated_at: nil}

It is happening because here in the decode_embed function, ecto is already loading the parameterized fields.

ecto_adapters_dynamodb/lib/ecto_adapters_dynamodb.ex

Lines 1567 to 1580 in 4762bab

 defp decode_embed(val, type) do 
   case Ecto.Type.embedded_load(type, val, :json) do 
     {:ok, decoded_value} -> 
       decoded_value 
  
     :error -> 
       ecto_dynamo_log( 
         :info, 
         "#{inspect(__MODULE__)}.decode_embed: failed to decode embedded value: #{inspect(val)}" 
       ) 
  
       nil 
   end 
 end 

This issue also happens on embedded_schemas with parameterized fields. I tried to remove the decode_embed function usage to test and it seems like we need it for embeds because other fields like utc_datetime type should already be loaded as its right type which is the opposite behavior for parameterized fields.

 ** (ArgumentError) cannot load `"2022-01-04T16:36:56Z"` as type :utc_datetime for field `inserted_at` in schema Ecto.Adapters.DynamoDB.TestSchema.Address

What alternatives do we have to handle this issue? I would be glad to open a merge request with the fix :)

[Gilad Barkan]

Thank you for alerting us to this issue. We would welcome a merge request. Thank you!