I assume its a beam issue i have. I don’t know honestly.

Setup

• my project contains fallowing module:

defmodule MyApp.Access do
  def permissions() do
    %{
      permission_x: [:list, :show],
      ...
    }
  end
end

In total project has 7 places where this atom permission_x is hardcoded.

Steps to consistently reproduce issue.

1. open new terminal tab.
2. ~ mix phx.server → server starts
3. in browser i request 127.0.0.1:4000 → i get error. This error seems odd, as i have module where required atom is hardcoded, so how can it be not an already existing atom, but ok?

[error] #PID<0.766.0> running MayAppWeb.Endpoint (connection #PID<0.765.0>, stream id 1) terminated
Server: 127.0.0.1:4000 (http)
Request: GET /
** (exit) an exception was raised:
    ** (ArgumentError) errors were found at the given arguments:

  * 1st argument: not an already existing atom

        :erlang.binary_to_existing_atom("permission_x", :utf8)

4. I make arbitrary change to MyApp.Access module: (can’t add empty line, as on-save it is removed by formatter, so just added :ok)

defmodule MyApp.Access do
+ :ok
  def permissions() do

5. in browser i request 127.0.0.1:4000 → and it works → terminal output:

Compiling 4 files (.ex)
[info] GET /
[info] Sent 200 in 262ms

7. I can remove :ok line and it keeps working. → I assume compilation part is the secret sauce that fixes issue.

If i stop server ctrl+c and start again (step 2). im back in step 3. it does not work again. and i need to do some arbitrary changes to MyApp.Access to force compilation.

Is there a way to see what files are compiled there? Maybe there is some secret.
Also why it after restart loads old/stale binary of MyApp.Access not the latest one that worked?

I have spent a lot time to debug this and i dont understand what could even be next steps to try to fix this.