No Init Lists

Lists as the argument for the init/1 callback should be avoided when implementing gen_* behaviors; use a tuple, a map, or a record instead.

Avoid

-behaviour(gen_server).

start_link(Name, Timeout) ->
    gen_server:start_link(?MODULE, _Args = [Name, Timeout], _Options = []).

init([Name, Timeout]) ->
    {ok, #{state => {Name, Timeout}}}.

Prefer

Using a map as an example:

-behaviour(gen_server).

start_link(Name, Timeout) ->
    gen_server:start_link(?MODULE, _Args = #{name => Name, timeout => Timeout}, _Options = []).

init(#{name := Name, timeout := Timeout}) ->
    {ok, #{state => {Name, Timeout}}}.

Rationale

When implementing gen_server, gen_statem, or other gen_* behaviors, using a list as the argument to the init/1 callback is discouraged. Tuples, maps, and records provide clearer structure, better pattern matching, and improved readability. Lists are typically used for variable-length collections and may lead to ambiguous or less maintainable code in this context.

Reference

Erlang Forums - Args in gen_*:init/1

Options

• behaviours :: [atom()] - list the behaviours for which you want to apply the rule
  • default: [gen_server, gen_statem, gen_fsm, supervisor, supervisor_bridge, gen_event]

Example configuration

{elvis_style, no_init_lists, #{
    behaviours => [
        gen_server,
        gen_statem,
        gen_fsm,
        supervisor,
        supervisor_bridge,
        gen_event
    ]
}}