Add optional callbacks

Mostly useful for REST, which has a ton. This is an initial
commit, it still needs to be tested, but it's time to sleep.

doc/src/manual/cowboy_rest.ezdoc

@@ -290,6 +290,10 @@ the same format as the etag header, including quotes.
 * Value type: true | {false, AuthHeader}
 * Default value: true
 
+Types:
+
+* AuthHead = iodata()
+
 Return whether the user is authorized to perform the action.
 
 This function should be used to perform any necessary
@@ -380,6 +384,10 @@ the request body, which is processed later.
 * Value type: {true, URL} | false
 * Default value: false
 
+Types:
+
+* URL = iodata()
+
 Return whether the resource was permanently moved.
 
 If it was, its new URL is also returned and sent in the
@@ -391,6 +399,10 @@ location header in the response.
 * Value type: {true, URL} | false
 * Default value: false
 
+Types:
+
+* URL = iodata()
+
 Return whether the resource was temporarily moved.
 
 If it was, its new URL is also returned and sent in the

src/cowboy_handler.erl

@@ -29,7 +29,9 @@
 	| {module(), Req, any(), timeout()}
 	| {module(), Req, any(), timeout(), hibernate}
 	when Req::cowboy_req:req().
-%% @todo optional -callback terminate(terminate_reason(), cowboy_req:req(), state()) -> ok.
+
+-callback terminate(any(), cowboy_req:req(), any()) -> ok.
+-optional_callbacks([terminate/3]).
 
 -spec execute(Req, Env) -> {ok, Req, Env}
 	when Req::cowboy_req:req(), Env::cowboy_middleware:env().

src/cowboy_loop.erl

@@ -38,7 +38,9 @@
 	| {ok, Req, State, hibernate}
 	| {stop, Req, State}
 	when Req::cowboy_req:req(), State::any().
-%% @todo optional -callback terminate(terminate_reason(), cowboy_req:req(), state()) -> ok.
+
+-callback terminate(any(), cowboy_req:req(), any()) -> ok.
+-optional_callbacks([terminate/3]).
 
 -record(state, {
 	env :: cowboy_middleware:env(),

src/cowboy_rest.erl

@@ -19,14 +19,183 @@
 
 -export([upgrade/6]).
 
+%% Common handler callbacks.
+
 -callback init(Req, any())
 	-> {ok | module(), Req, any()}
 	| {module(), Req, any(), hibernate}
 	| {module(), Req, any(), timeout()}
 	| {module(), Req, any(), timeout(), hibernate}
 	when Req::cowboy_req:req().
-%% @todo optional REST callbacks
+
-%% @todo optional -callback terminate(terminate_reason(), cowboy_req:req(), state()) -> ok.
+-callback terminate(any(), cowboy_req:req(), any()) -> ok.
+-optional_callbacks([terminate/3]).
+
+%% REST handler callbacks.
+
+-callback allowed_methods(Req, State)
+	-> {[binary()], Req, State}
+	| {stop, Req, State}
+	when Req::cowboy_req:req(), State::any().
+-optional_callbacks([allowed_methods/2]).
+
+-callback allow_missing_post(Req, State)
+	-> {boolean(), Req, State}
+	| {stop, Req, State}
+	when Req::cowboy_req:req(), State::any().
+-optional_callbacks([allow_missing_post/2]).
+
+-callback charsets_provided(Req, State)
+	-> {[binary()], Req, State}
+	| {stop, Req, State}
+	when Req::cowboy_req:req(), State::any().
+-optional_callbacks([charsets_provided/2]).
+
+-callback content_types_accepted(Req, State)
+	-> {[{binary() | {binary(), binary(), '*' | [{binary(), binary()}]}, atom()}], Req, State}
+	| {stop, Req, State}
+	when Req::cowboy_req:req(), State::any().
+-optional_callbacks([content_types_accepted/2]).
+
+-callback content_types_provided(Req, State)
+	-> {[{binary() | {binary(), binary(), '*' | [{binary(), binary()}]}, atom()}], Req, State}
+	| {stop, Req, State}
+	when Req::cowboy_req:req(), State::any().
+-optional_callbacks([content_types_provided/2]).
+
+-callback delete_completed(Req, State)
+	-> {boolean(), Req, State}
+	| {stop, Req, State}
+	when Req::cowboy_req:req(), State::any().
+-optional_callbacks([delete_completed/2]).
+
+-callback delete_resource(Req, State)
+	-> {boolean(), Req, State}
+	| {stop, Req, State}
+	when Req::cowboy_req:req(), State::any().
+-optional_callbacks([delete_resource/2]).
+
+-callback expires(Req, State)
+	-> {calendar:datetime() | binary() | undefined, Req, State}
+	| {stop, Req, State}
+	when Req::cowboy_req:req(), State::any().
+-optional_callbacks([expires/2]).
+
+-callback forbidden(Req, State)
+	-> {boolean(), Req, State}
+	| {stop, Req, State}
+	when Req::cowboy_req:req(), State::any().
+-optional_callbacks([forbidden/2]).
+
+-callback generate_etag(Req, State)
+	-> {binary() | {weak | strong, binary()}, Req, State}
+	| {stop, Req, State}
+	when Req::cowboy_req:req(), State::any().
+-optional_callbacks([generate_etag/2]).
+
+-callback is_authorized(Req, State)
+	-> {true | {false, iodata()}, Req, State}
+	| {stop, Req, State}
+	when Req::cowboy_req:req(), State::any().
+-optional_callbacks([is_authorized/2]).
+
+-callback is_conflict(Req, State)
+	-> {boolean(), Req, State}
+	| {stop, Req, State}
+	when Req::cowboy_req:req(), State::any().
+-optional_callbacks([is_conflict/2]).
+
+-callback known_methods(Req, State)
+	-> {[binary()], Req, State}
+	| {stop, Req, State}
+	when Req::cowboy_req:req(), State::any().
+-optional_callbacks([known_methods/2]).
+
+-callback languages_provided(Req, State)
+	-> {[binary()], Req, State}
+	| {stop, Req, State}
+	when Req::cowboy_req:req(), State::any().
+-optional_callbacks([languages_provided/2]).
+
+-callback last_modified(Req, State)
+	-> {calendar:datetime(), Req, State}
+	| {stop, Req, State}
+	when Req::cowboy_req:req(), State::any().
+-optional_callbacks([last_modified/2]).
+
+-callback malformed_request(Req, State)
+	-> {boolean(), Req, State}
+	| {stop, Req, State}
+	when Req::cowboy_req:req(), State::any().
+-optional_callbacks([malformed_request/2]).
+
+-callback moved_permanently(Req, State)
+	-> {{true, iodata()} | false, Req, State}
+	| {stop, Req, State}
+	when Req::cowboy_req:req(), State::any().
+-optional_callbacks([moved_permanently/2]).
+
+-callback moved_temporarily(Req, State)
+	-> {{true, iodata()} | false, Req, State}
+	| {stop, Req, State}
+	when Req::cowboy_req:req(), State::any().
+-optional_callbacks([moved_temporarily/2]).
+
+-callback multiple_choices(Req, State)
+	-> {boolean(), Req, State}
+	| {stop, Req, State}
+	when Req::cowboy_req:req(), State::any().
+-optional_callbacks([multiple_choices/2]).
+
+-callback options(Req, State)
+	-> {ok, Req, State}
+	| {stop, Req, State}
+	when Req::cowboy_req:req(), State::any().
+-optional_callbacks([options/2]).
+
+-callback previously_existed(Req, State)
+	-> {boolean(), Req, State}
+	| {stop, Req, State}
+	when Req::cowboy_req:req(), State::any().
+-optional_callbacks([previously_existed/2]).
+
+-callback resource_exists(Req, State)
+	-> {boolean(), Req, State}
+	| {stop, Req, State}
+	when Req::cowboy_req:req(), State::any().
+-optional_callbacks([resource_exists/2]).
+
+-callback service_available(Req, State)
+	-> {boolean(), Req, State}
+	| {stop, Req, State}
+	when Req::cowboy_req:req(), State::any().
+-optional_callbacks([service_available/2]).
+
+-callback uri_too_long(Req, State)
+	-> {boolean(), Req, State}
+	| {stop, Req, State}
+	when Req::cowboy_req:req(), State::any().
+-optional_callbacks([uri_too_long/2]).
+
+-callback valid_content_headers(Req, State)
+	-> {boolean(), Req, State}
+	| {stop, Req, State}
+	when Req::cowboy_req:req(), State::any().
+-optional_callbacks([valid_content_headers/2]).
+
+-callback valid_entity_length(Req, State)
+	-> {boolean(), Req, State}
+	| {stop, Req, State}
+	when Req::cowboy_req:req(), State::any().
+-optional_callbacks([valid_entity_length/2]).
+
+-callback variances(Req, State)
+	-> {[binary()], Req, State}
+	| {stop, Req, State}
+	when Req::cowboy_req:req(), State::any().
+-optional_callbacks([variances/2]).
+
+%% End of REST callbacks. Whew!
 
 -record(state, {
 	env :: cowboy_middleware:env(),

src/cowboy_websocket.erl

@@ -45,7 +45,9 @@
 	| {reply, cow_ws:frame() | [cow_ws:frame()], Req, State, hibernate}
 	| {stop, Req, State}
 	when Req::cowboy_req:req(), State::any().
-%% @todo optional -callback terminate(terminate_reason(), cowboy_req:req(), state()) -> ok.
+
+-callback terminate(any(), cowboy_req:req(), any()) -> ok.
+-optional_callbacks([terminate/3]).
 
 -record(state, {
 	env :: cowboy_middleware:env(),