dbg() stopped working on OTP 28

[gmile]

Elixir and Erlang/OTP versions

Erlang/OTP 28 [erts-16.0.1] [source] [64-bit] [smp:16:16] [ds:16:16:10] [async-threads:1] [jit]

Elixir 1.18.4 (compiled with Erlang/OTP 28)

Operating system

macOS

Current behavior

This script:

# issue-example.exs
a = 1
b = 2

dbg()

IO.puts(a + b)

(code besides dbg() itself is not significant here, it's just here so the script is not completely empty)

Running the above like this:

iex --dbg pry issue-example.exs

Results in the following output:

Erlang/OTP 28 [erts-16.0.1] [source] [64-bit] [smp:16:16] [ds:16:16:10] [async-threads:1] [jit]

Cannot pry #PID<0.107.0> at sample.exs:4. Is an IEx shell running?
binding() #=> [a: 1, b: 2]

3
Interactive Elixir (1.18.4) - press Ctrl+C to exit (type h() ENTER for help)

Note the Cannot pry #PID<0.107.0> at sample.exs:4. Is an IEx shell running? message.

Expected behavior

Script execution stops at dbg() breakpoint for debugging.

[Aetherus]

Erlang version: 28.0.1
Elixir version: 1.18.4-otp-28
Operating System: Pop!_OS 22.04 LTS

I just tried iex --dbg pry, type dbg() in the iex shell, and I saw the message Cannot pry #PID<0.105.0> at iex:1. Is an IEx shell running?

[Aetherus]

It seems that the process named :user is different between OTP 27 and 28, but I'm not capable of further digging.

user = Process.whereis(:user)
Process.info(user, :initial_call)

OTP 27 shows {:initial_call, {:group, :server, 4}}
OTP 28 shows {:initial_call, {:proc_lib, :init_p, 5}}, and there's no :user_drv in that process's dictionary.

[josevalim]

Fixed on 3482e4e but I forgot to link back. :)