crash creating invites: handle misconfiguration more gracefully

[sstrigler]

2026-02-11 09:41:26.800268-06:00 [error] <0.662.0>@mod_http_api:handle/4:259 REST API Error:
 generate_invite([{<<"host">>,<<"example.org">>}]) ->
 error:{badmatch, error}
 [{mod_invites_http, tmpl_to_renderer, 1,
  [{file, "src/mod_invites_http.erl"},
   {line, 362}]},
 {mod_invites_http, render_url, 2,
  [{file, "src/mod_invites_http.erl"},
   {line, 317}]},
 {mod_invites, gen_invite, 2,
  [{file, "src/mod_invites.erl"},
   {line, 429}]},
 {mod_invites, generate_invite, 2,
  [{file, "src/mod_invites.erl"},
   {line, 410}]},
 {ejabberd_commands, do_execute_command, 2,
  [{file, "src/ejabberd_commands.erl"},
   {line, 324}]},
 {mod_http_api, handle2, 4,
  [{file, "src/mod_http_api.erl"},
   {line, 272}]},
 {mod_http_api, handle, 4,
  [{file, "src/mod_http_api.erl"},
   {line, 231}]},
 {erpc, execute_call, 4,
  [{file, "erpc.erl"},
   {line, 1262}]}]

[sstrigler]

v 26.02 installed from official debian repo

[sstrigler]

From their config

modules:
  mod_invites:
    landing_page: "https://invites.example.org:443/join/#{{ invite.uri|strip.protocol }}"
  ...
  mod_register:
  ip_access: trusted_network
  allow_modules:
    - mod_invites

needs to be

    landing_page: "https://invites.example.org:443/join/#{{ invite.uri|strip_protocol }}"

Note the '_' instead of '.' in strip_protocol.

Wonder if we can't handle this more gracefully.

[badlop]

The problem is that the option requires some specific syntax, but mod_opt_type(landing_page) performs only basic testing: if it's 'none', 'auto' or a binary.

Consequently, the configuration problem is not detected when reading the configuration, but later when the option value is used.

The solution is to improve mod_opt_type(landing_page) to perform a more detailed validation. I think something like that is implemented for other options, and can serve as example code:

• src/mod_adhoc_api.erl: mod_opt_type(default_version)
• src/mod_vcard_ldap.erl: mod_opt_type(ldap_uids)

[prefiks]

To be able to use custom error messages you can use something like this:

-export(format_error/1).

format(Fmt, Args) ->
    lists:flatten(io_lib:format(Fmt, Args)).

format_error({invalid_value, Param}) ->
    format("Paramater: ~ts is not valid", [Param]).

fail(Reason) ->
    yconf:fail(econf, {external_module_error, ?MODULE, Reason}).

mod_opt_type(test) ->
    econf:and_then(econf:binary(),
        fun(Value) ->
          case Value of
            <<"ok">> -> <<"ok">>;
            _ -> fail({invalid_value, Value})
          end
       end).

[badlop]

I've implemented verification of the value syntax and more clear explanation of the problem. I guess this will be enough to guide the administrator to the solution.

2026-02-23 16:45:45.579387+01:00 [info] Loading configuration from _build/relive/conf/ejabberd.yml

2026-02-23 16:45:45.887273+01:00 [critical] There is some problem in the value you configured for option
  'landing_page' in 'mod_invites'. Please consult the documentation and fix it:
  https://invites.example.org:443/join/#{{ invite.uri|strip.protocol }}

2026-02-23 16:45:45.896361+01:00 [critical] Failed to start ejabberd application: Exception occurred during configuration processing. This is most likely due to faulty/incompatible validator in third-party code. If you are not running any third-party code, please report the bug with ejabberd configuration file attached and the following stacktrace included:
** exception throw: {error,<<"There is some problem in the value you configured for option 'landing_page' in 'mod_invites'. Please consult the documentation and fix it: https://invites.example.org:443/join/#{{ invite.uri|strip.protocol }}">>}
   in function  mod_invites:'-mod_opt_type/1-fun-0-'/1 (/home/test/e/git/ejabberd/src/mod_invites.erl:310)
   in call from yconf:validate_option/3 (/home/test/e/git/ejabberd/_build/default/lib/yconf/src/yconf.erl:1281)
   in call from yconf:validate_options/8 (/home/test/e/git/ejabberd/_build/default/lib/yconf/src/yconf.erl:1258)
   in call from yconf:'-and_then/2-fun-0-'/3 (/home/test/e/git/ejabberd/_build/default/lib/yconf/src/yconf.erl:620)
   in call from yconf:validate_option/3 (/home/test/e/git/ejabberd/_build/default/lib/yconf/src/yconf.erl:1281)
   in call from yconf:validate_options/8 (/home/test/e/git/ejabberd/_build/default/lib/yconf/src/yconf.erl:1258)
   in call from yconf:validate_option/3 (/home/test/e/git/ejabberd/_build/default/lib/yconf/src/yconf.erl:1281)
   in call from yconf:validate_options/8 (/home/test/e/git/ejabberd/_build/default/lib/yconf/src/yconf.erl:1258)