namespaced provider with options

rebar3_rust_compile_prv.erl

-module(rebar3_rust_compile_prv).

-export([init/1, do/1, format_error/1]).

-include_lib("kernel/include/file.hrl").

-define(PROVIDER, build).
-define(NAMESPACE, rust).
-define(DEPS, [{default,app_discovery}]).

%% ===================================================================
%% Public API
%% ===================================================================
-spec init(rebar_state:t()) -> {ok, rebar_state:t()}.
init(State) ->
    Provider = providers:create([
            {name, ?PROVIDER},               % The 'user friendly' name of the task
            {namespace, ?NAMESPACE},
            {module, ?MODULE},               % The module implementation of the task
            {bare, true},                    % The task can be run by the user, always true
            {deps, ?DEPS},                   % The list of dependencies
            {example, "rebar3 rust build"},  % How to use the plugin

            %% list of options understood by the plugin
            {opts, [
                {extern_crates, undefined, "extern_crates",
                 string, "Crates from crates.io to build for this app"}
            ]},

            {short_desc, "Compile Rust crates"},
            {desc, "Compile Rust crates"}
    ]),
    {ok, rebar_state:add_provider(State, Provider)}.