erlang_ls should be more explicit when it finds an erlang_ls.config that isn't valid

[ollien]

Is your feature request related to a problem? Please describe.

Right now, if erlang_ls.config is not valid, erlang_ls will log it and move on, but it is not always abundantly clear that this has happened. For instance

[2022-11-07T11:22:18.612874-05:00] [debug] Could not read config file: path="/home/nick/Documents/code/my_project/erlang_ls.config" class=throw error={yamerl_exception,[{yamerl_parsing_error,error,"Unexpected \"yamerl_scalar\" token following a \"yamerl_scalar\" token",2,1,unexpected_token,{yamerl_scalar,2,1,{yamerl_tag,2,1,{non_specific,"?"}},flow,plain,"plt_path \"/home/nick/Documents/code/my_project/_build/default/rebar3_21.3.8.4_plt\""},[]}]} [els_config:consult_config/1 L350] <0.148.0>

On my system, where I have no global erlang_ls.config, this manifests itself in VSCode with an alert saying there's no erlang_ls.config file.

Describe the solution you'd like
I think there's a few ways this could be tackled

1. At minimum, the above log could be bumped up from a DEBUG to a WARN or ERROR.
2. Editors like VSCode could give a more explicit error that a config file was invalid, much like there is when there is no config file.
3. erlang_ls should maybe stop execution if this happens. I can think of very few cases where someone might want to continue operation after a configuration is determined to be invalid; falling back to the next available config ironically masks the problem, since it might not be obvious that this occurred.

Describe alternatives you've considered
See previous section

Additional context
This thread in the Erlang slack is where this originally came up

[fabjan]

Agree on all points.

I think an error level log with details, an error notice (the name of the concept in the lsp eludes me) should be shown, and the language server should exit with an error.