Write some convenience helpers

3 files changed, 67 insertions, 19 deletions

diff --git a/lib/stdlib/doc/src/gen_statem.xml b/lib/stdlib/doc/src/gen_statem.xml
index aeab09615c..5fbedb12f8 100644
--- a/lib/stdlib/doc/src/gen_statem.xml
+++ b/lib/stdlib/doc/src/gen_statem.xml
@@ -535,6 +535,13 @@ erlang:'!'            -----> Module:StateName/5
       <desc>
 	<taglist>
 	  <tag>
+	   <c>{stop,<anno>Reason</anno>}</c>
+	  </tag>
+	  <item>The same as
+	    <c>{stop,<anno>Reason</anno>,[],StateData}</c>
+	    but keeps the old <c>StateData</c>.
+	  </item>
+	  <tag>
 	   <c>{stop,<anno>Reason</anno>,<anno>NewStateData</anno>}</c>
 	  </tag>
 	  <item>The same as
@@ -553,6 +560,19 @@ erlang:'!'            -----> Module:StateName/5
 	  </item>
 	  <tag>
 	    <c>
+	      {next_state,<anno>StateOps</anno>}
+	    </c>
+	  </tag>
+	  <item>The same as
+	    <c>
+	      {next_state,State,StateData,<anno>StateOps</anno>}
+	    </c>but keeps the old <c>State</c> and <c>StateData</c>.
+	    Believe it or not, but this one has actually
+	    been proven useful to <c>throw/1</c> from deep down
+	    in the state logic.
+	  </item>
+	  <tag>
+	    <c>
 	      {next_state,<anno>NewState</anno>,<anno>NewStateData</anno>}
 	    </c>
 	  </tag>
@@ -805,6 +825,7 @@ erlang:'!'            -----> Module:StateName/5
     </func>
 
     <func>
+      <name name="reply" arity="1" />
       <name name="reply" arity="2" />
       <fsummary>Send a reply to a client</fsummary>
       <desc>
@@ -820,6 +841,8 @@ erlang:'!'            -----> Module:StateName/5
 	    <c>{call,<anno>Client</anno>}</c>
 	  </seealso> argument to the
 	  <seealso marker="#state_function">state function</seealso>.
+	  <c><anno>Client</anno></c> and <c><anno>Reply</anno></c>
+	  an also be specified using <c><anno>ReplyOperation</anno></c>.
 	</p>
 	<note>
 	  <p>A reply sent with this function will not be visible
diff --git a/lib/stdlib/src/gen_statem.erl b/lib/stdlib/src/gen_statem.erl
index 32174687cf..486f61b1ed 100644
--- a/lib/stdlib/src/gen_statem.erl
+++ b/lib/stdlib/src/gen_statem.erl
@@ -25,7 +25,7 @@
     stop/1,stop/3,
     cast/2,call/2,call/3,
     enter_loop/4,enter_loop/5,enter_loop/6,
-    reply/2]).
+    reply/1,reply/2]).
 
 %% gen callbacks
 -export(
@@ -105,17 +105,21 @@
 	{'reply', % Reply to a client
 	 Client :: client(), Reply :: term()}.
 -type state_callback_result() ::
-    {stop, % Stop the server
+    {'stop', % Stop the server
+     Reason :: term()} |
+    {'stop', % Stop the server
      Reason :: term(),
      NewStateData :: state_data()} |
-    {stop, % Stop the server
+    {'stop', % Stop the server
      Reason :: term(),
      Replies :: [reply_operation()] | reply_operation(),
      NewStateData :: state_data()} |
-    {next_state, % {next_state,NewState,NewStateData,[]}
+    {'next_state', % {next_state,State,StateData,StateOps} % Actually useful
+     StateOps :: [state_op()] | state_op()} |
+    {'next_state', % {next_state,NewState,NewStateData,[]}
      NewState :: state(),
      NewStateData :: state_data()} |
-    {next_state, % State transition, maybe to the same state
+    {'next_state', % State transition, maybe to the same state
      NewState :: state(),
      NewStateData :: state_data(),
      StateOps :: [state_op()] | state_op()}.
@@ -379,6 +383,10 @@ call(ServerRef, Request, Timeout) ->
     end.
 
 %% Reply from a state machine callback to whom awaits in call/2
+-spec reply(ReplyOperation :: reply_operation()) -> ok.
+reply({reply,{_To,_Tag}=Client,Reply}) ->
+    reply(Client, Reply).
+%%
 -spec reply(Client :: client(), Reply :: term()) -> ok.
 reply({To,Tag}, Reply) ->
     Msg = {Tag,Reply},
@@ -742,6 +750,8 @@ loop_events(
 %% Interpret all callback return value variants
 loop_event_result(Parent, Debug, S, Events, Event, Result) ->
     case Result of
+	{stop,Reason} ->
+	    ?TERMINATE(Reason, Debug, S, [Event|Events]);
 	{stop,Reason,NewStateData} ->
 	    ?TERMINATE(
 	      Reason, Debug,
@@ -764,6 +774,11 @@ loop_event_result(Parent, Debug, S, Events, Event, Result) ->
 	    ?TERMINATE(
 	      {bad_return_value,{stop,Reason,BadReplies,NewStateData}},
 	      Debug, NewS, Q);
+	{next_state,StateOps} ->
+	    #{state := State, state_data := StateData} = S,
+	    loop_event_state_ops(
+	      Parent, Debug, S, Events, Event,
+	      State, StateData, StateOps);
 	{next_state,NewState,NewStateData} ->
 	    loop_event_state_ops(
 	      Parent, Debug, S, Events, Event,
@@ -846,7 +861,12 @@ loop_event_state_ops(
 %% Server helpers
 
 collect_init_options(InitOps) ->
-    collect_init_options(InitOps, state_functions, []).
+    if
+	is_list(InitOps) ->
+	    collect_init_options(InitOps, state_functions, []);
+	true ->
+	    collect_init_options([InitOps], state_functions, [])
+    end.
 %% Keep the last of each kind
 collect_init_options([], CallbackMode, StateOps) ->
     {CallbackMode,lists:reverse(StateOps)};
@@ -864,7 +884,12 @@ collect_init_options([InitOp|InitOps] = IOIOs, CallbackMode, StateOps) ->
     end.
 
 collect_state_options(StateOps) ->
-    collect_state_options(StateOps, false, false, undefined, []).
+    if
+	is_list(StateOps) ->
+	    collect_state_options(StateOps, false, false, undefined, []);
+	true ->
+	    collect_state_options([StateOps], false, false, undefined, [])
+    end.
 %% Keep the last of each kind
 collect_state_options(
   [], Postpone, Hibernate, Timeout, Operations) ->
diff --git a/lib/stdlib/test/gen_statem_SUITE.erl b/lib/stdlib/test/gen_statem_SUITE.erl
index 8b619b6a60..6249ada027 100644
--- a/lib/stdlib/test/gen_statem_SUITE.erl
+++ b/lib/stdlib/test/gen_statem_SUITE.erl
@@ -1158,11 +1158,10 @@ idle(cast, badreturn, _, _, _Data) ->
     badreturn;
 idle({call,_From}, badreturn, _, _, _Data) ->
     badreturn;
-idle({call,From}, {delayed_answer,T}, _, State, Data) ->
+idle({call,From}, {delayed_answer,T}, _, _, _) ->
     receive
     after T ->
-	    {next_state,State,Data,
-	     [{reply,From,delayed}]}
+	    throw({next_state,{reply,From,delayed}})
     end;
 idle({call,From}, {timeout,Time}, _, State, _Data) ->
     {next_state,timeout,{From,Time},
@@ -1172,9 +1171,10 @@ idle(Type, Content, PrevState, State, Data) ->
 	undefined ->
 	    case Type of
 		{call,From} ->
-		    {next_state,State,Data,[{reply,From,'eh?'}]};
+		    throw({next_state,[{reply,From,'eh?'}]});
 		_ ->
-		    {stop,{unexpected,State,PrevState,Type,Content},Data}
+		    throw(
+		      {stop,{unexpected,State,PrevState,Type,Content}})
 	    end;
 	Result ->
 	    Result
@@ -1208,8 +1208,8 @@ timeout3(_, _, _, State, Data) ->
 wfor_conf({call,From}, confirm, _, _, Data) ->
     {next_state,connected,Data,
      [{reply,From,yes}]};
-wfor_conf(cast, {ping,_,_}, _, State, Data) ->
-    {next_state,State,Data,[postpone]};
+wfor_conf(cast, {ping,_,_}, _, _, _) ->
+    {next_state,[postpone]};
 wfor_conf(cast, confirm, _, _, Data) ->
     {next_state,connected,Data};
 wfor_conf(Type, Content, PrevState, State, Data) ->
@@ -1220,7 +1220,7 @@ wfor_conf(Type, Content, PrevState, State, Data) ->
 		    {next_state,idle,Data,
 		     [{reply,From,'eh?'}]};
 		_ ->
-		    {next_state,State,Data}
+		    throw({next_state,[]})
 	    end;
 	Result ->
 	    Result
@@ -1320,12 +1320,12 @@ handle_common_events(cast, {get,Pid}, _, State, Data) ->
     {next_state,State,Data};
 handle_common_events({call,From}, stop, _, _, Data) ->
     {stop,normal,[{reply,From,stopped}],Data};
-handle_common_events(cast, stop, _, _, Data) ->
-    {stop,normal,Data};
+handle_common_events(cast, stop, _, _, _) ->
+    {stop,normal};
 handle_common_events({call,From}, {stop,Reason}, _, _, Data) ->
     {stop,Reason,{reply,From,stopped},Data};
-handle_common_events(cast, {stop,Reason}, _, _, Data) ->
-     {stop,Reason,Data};
+handle_common_events(cast, {stop,Reason}, _, _, _) ->
+     {stop,Reason};
 handle_common_events({call,From}, 'alive?', _, State, Data) ->
     {next_state,State,Data,
      [{reply,From,yes}]};