This was indeed an issue w/ the :embedded reference there. In Ash, there is a short-hand of data_layer: :embedded. We were treating that as an extension module in spark and attempting to call a function on it. This is fixed in 2.3.7 of spark.

Hey @josevalim I made a reproducible example, here is the link: GitHub - sezaru/test_new_elixir

Basically you just need to compile it using MIX_ENV=test mix compile

it will generate the following warning:

> MIX_ENV=test mix compile --force
Compiling 6 files (.ex)
    warning: you are implementing a protocol for Core.Marketplace.Chat.PropertyMessage but said module is not available. Make sure the module name is correct. If Core.Marketplace.Chat.PropertyMessage is an optional dependency, please wrap the protocol implementation in a Code.ensure_loaded?(Core.Marketplace.Chat.PropertyMessage) check
    │
  1 │ defimpl Core.Support.Factory.Builder, for: Core.Marketplace.Chat.PropertyMessage do
    │ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    │
    └─ test/support/factory/marketplace/chat/property_message.ex:1: (file)

Making the example, basically what makes this warning appears or not is the line 11 of the file lib/core/marketplace/chat/property_message.ex:

    attribute :attachments, {:array, Attachment}, default: []

This lines add the embedded Ash resource Attachment as an attribute of my Ash resource PropertyMessage.

If I remove that line, then the warning disappears.

The same code works fine in Elixir 1.18.

Maybe @zachdaniel knows why this triggers the warning?

If I remove Ash, then it works. By using –profile time, we can see that Ash is deadlocking the compiler:

$ MIX_ENV=test mix compile --force --profile time
Compiling 6 files (.ex)
[profile]      9ms compiling +      0ms waiting while compiling lib/core/application.ex
[profile]     31ms compiling +      0ms waiting while compiling test/support/factory/builder.ex
[profile]    164ms compiling +      0ms waiting while compiling lib/core/marketplace/chat.ex
[profile] Finished deadlock resolution in 0ms
[profile]     15ms compiling +    133ms waiting for module Core.Marketplace.Chat.PropertyMessage while compiling test/support/factory/marketplace/chat/property_message.ex
[profile]                    |     24ms waiting for module Core.Support.Factory.Builder while compiling test/support/factory/marketplace/chat/property_message.ex
[profile] Finished deadlock resolution in 0ms
[profile]    447ms compiling +    167ms waiting for module :embedded while compiling lib/core/marketplace/chat/attachment.ex
[profile]    239ms compiling +    552ms waiting for module Core.Marketplace.Chat.Attachment while compiling lib/core/marketplace/chat/property_message.ex

The fact that attachment is waiting for :embedded also points to what is more likely a bug. My suggestion is for Ash to move some of the validations in its DSL to verify callbacks. If the compiler is deadlocked, then it assumes the modules are not there, leading to the warning.

I just did a quick test and, indeed, seem to be fixed, thanks!