Type from map and type from parent are equal

[josv]

polymorphic_embed/lib/polymorphic_embed.ex

Line 361 in 5713d6c

cond do

The case where the type from the map equals the type from the parent, is not handled, and will raise a missing truthy value error. Is that intended behavior?

[cheerfulstoic]

I think I'm seeing the same thing! Here's the top of the error:

** (CondClauseError) no cond clause evaluated to a truthy value
    (polymorphic_embed 5.0.3) lib/polymorphic_embed.ex:361: PolymorphicEmbed.action_and_struct/4
    (polymorphic_embed 5.0.3) lib/polymorphic_embed.ex:309: PolymorphicEmbed.cast_polymorphic_embeds_one/5
    ...

I'm using the use_parent_field_for_type option, which I think is part of the problem.

[ringvold]

I have bumped into this situation more than once now, so either I'm consistently doing something wrong or there is something missing here. I'm also using the use_parent_field_for_type.

I forgot the fix between the times I ran into this so I'm posting mine here for others or myself later 😄 :

{_, params} =
      params
      |> pop_in(~w(fields __type__))

It's basically removing the type in the map and forcing it to use the type defined in the parent schema. The polymorpic_embed field is creatively called fields in this case.

I feel like this should not be a problem though, as there is no type ambiguation. All sources agree about the type. When there is type ambiguation the current last case of the cond raises with a message about this.

Could it be as simple as making the content of the is_nil(type_from_map) branch the default one?
Like so:

true ->
    module = get_polymorphic_module_for_type(type_from_parent_field, types_metadata)

    if is_nil(data_for_field) or data_for_field.__struct__ != module do
      {:insert, struct(module)}
    else
      {:update, data_for_field}
    end