Format the error reason and stack back-trace caught using try ... catch in the same style as the shell formats them.

Example:

try
    do_something()
catch
    C:R:Stk ->
        Message = erl_error:format_exception(C, R, Stk),
        io:format(LogFile, "~ts\n", [Message])
end

If error_info is provided with the exception, format_exception will use that information to provide additional information about the exception.

Example:

try
  erlang:raise(badarg,[],[{error_info,#{}}])
catch
    C:R:Stk ->
        Message = erl_error:format_exception(C, R, Stk),
        io:format(LogFile, "~ts\n", [Message])
end

See erlang:error/3 for details on how to raise an exception with error_info included.

Types

This callback is called when format_exception/4 or similar functionality wants to provide extra information about an error. The Module:Function called is the one specificed by the error_info map.

The function should return a map with additional information about what have caused the exception. The possible keys of the map are:

ArgumentPosition = pos_integer()

The position of the argument that caused the error starting at 1.

general

An error that is not associated with any argument caused the error.

reason

If the Reason should be printed differently than the default way.

If the text returned includes new-lines, format_exception/4 will indent the text correctly.

Example:

-module(my_error_module).
-export([atom_to_string/1, format_error/2]).

atom_to_string(Arg) when is_atom(Arg) ->
  atom_to_list(Arg);
atom_to_string(Arg) ->
  erlang:error(badarg,[Arg],
               [{error_info,#{ module => ?MODULE,
                               cause => #{ 1 => "should be an atom" }}}]).

format_error(Reason, [{_M,_F,_As,Info}|_]) ->
  ErrorInfo = proplists:get_value(error_info, Info, #{}),
  ErrorMap = maps:get(cause, ErrorInfo),
  ErrorMap#{ general => "optional general information",
             reason => io_lib:format("~p: ~p",[?MODULE, Reason]) }.

1> c(my_error_module).
{ok,my_error_module}
2> my_error_module:atom_to_string(1).
** exception error: my_error_module: badarg
     in function  my_error_module:atom_to_string/1
        called as my_error_module:atom_to_string(1)
        *** argument 1: should be an atom
        *** optional general information