How do I debug rebar3 erlang in vscode with the erlang plugin? - debugging

Question

I am using the Erlang language plugin for vscode. I created a new rebar3 app and created a simple app that doesnt use a supervisor:
-module(test_app_app).
-behaviour(application).
-export([start/2, stop/1]).
start(_StartType, _StartArgs) ->
load_file("input.txt").
stop(_State) ->
ok.
load_file(Filename) ->
case file:read_file(Filename) of
{ok, Bin} ->
Bin;
{error, Reason} ->
erlang:error(Reason)
end.
I have configured a launch.json file like so:
{
"version": "0.2.0",
"configurations": [
{
"name": "Launch erlang",
"type": "erlang",
"request": "launch",
"cwd": "${workspaceRoot}",
"arguments": "-s test_app_app start",
"preLaunchTask": "rebar3 compile"
}
]
}
and a tasks.json for the compile:
{
"version": "2.0.0",
"tasks": [
{
"label": "rebar3 compile",
"type": "shell",
"command": "rebar3 compile",
"group": {
"kind": "build",
"isDefault": true
},
"problemMatcher": "$erlang"
}
]
}
When I hit F5 I get the following output:
compiling erlang bridge to '/home/peter/.vscode/extensions/pgourlain.erlang-0.8.1/_build/default/lib/ebin'
Compiling arguments file "/tmp/bp_1454870.erl"
Compile result: sucess
Module bp_1454870 loaded
{"init terminating in do_boot",{undef,[{t
est_app_app,start,[],[]},{init,start_em,1,[]},{init,do_boot,3,[]}]}}
init terminating in do_boot ({undef,[{test_app_app,start,[],[]},{init,start_em,1,[]},{init,do_boot,3,[]}]})
Crash dump is being written to: erl_crash.dump...
done
erl exit code:1
erl exit with code 1
Does anyone have a clue as to why this isnt working for me?

Answer 1

The problem is in your launch.json. You try to run a function start/0 from module test_app_app and such function does not exist.
Try to use
"arguments": "-eval \"application:start(test_app)\""