IEx Entrypoint "Elixir.IEx.CLI start()` no longer exists in Elixir v1.15.0+

[ashleysommer]

Describe the bug
IEx Entrypoint Elixir.IEx.CLI start() no longer exists.
The start() entrypoint was removed from Elixir v1.15

To Reproduce
Steps to reproduce the behavior:

1. Add a new Run/Debug configuration
2. Choose IEx Mix
3. Click Ok
4. Run the configuration

Expected behavior
Should run Mix in the IEx interactive Elixir prompt. This works fine in Elixir v1.14.x and below.

Logs

error_info: {error,undef,[{'Elixir.IEx.CLI',start,[],[]},{user_sup,start_user,3,[{file,"user_sup.erl"},{line,102}]},{user_sup,init,1,[{file,"user_sup.erl"},{line,51}]},{supervisor_bridge,init,1,[{file,"supervisor_bridge.erl"},{line,87}]},{gen_server,init_it,2,[{file,"gen_server.erl"},{line,980}]},{gen_server,init_it,6,[{file,"gen_server.erl"},{line,935}]},{proc_lib,init_p_do_apply,3,[{file,"proc_lib.erl"},{line,241}]}]}

Desktop:

• OS: Arch Linux

Erlang:

• Installer asdf
• Version 26

Elixir:

• Installer asdf
• Version 1.16.2

Plugin:

• Version 17.0

Additional context

See these two commits for the changes in v1.15.0
elixir-lang/elixir@e1eecb8
elixir-lang/elixir@c28b596

The correct full constructed cmdline to use in v1.15.0 is this:

/path/to/bin/erl -pa ... -s elixir start_cli -noshell -elixir ansi_enabled true -user elixir -extra +iex -e ":elixir.start_iex()"
 --no-halt -S /path/to/bin/mix

But that doesn't work in v1.15.1+ and v1.16.
They introduced yet another mechanism in v1.16 (and v1.15.1+ on the 1.15 branch).
elixir-lang/elixir@cc2d056
The correct full cmdline in v1.15.1+ and v1.16.0+ is this:

/path/to/bin/erl -pa ... -s elixir start_iex -noshell -elixir ansi_enabled true -user elixir -extra +iex --no-halt -S /path/to/bin/mix

[KronicDeth]

17.0.0

Confirmed working on 1.14.5
Confirmed broken on 1.15.0
Confirmed broken on 1.15.1
Confirmed broken on 1.16.2