From 1e4831762b5ab4bd2210fc9e0a204e00dfe81b39 Mon Sep 17 00:00:00 2001
From: Raimo Niskanen <raimo@erlang.org>
Date: Fri, 26 Feb 2016 10:35:16 +0100
Subject: Implement 'keep_state_and_data' and 'stop'

---
 lib/stdlib/doc/src/gen_statem.xml    |  7 ++++-
 lib/stdlib/src/gen_statem.erl        | 60 ++++++++++++++++++++----------------
 lib/stdlib/test/gen_statem_SUITE.erl |  4 +--
 3 files changed, 42 insertions(+), 29 deletions(-)

diff --git a/lib/stdlib/doc/src/gen_statem.xml b/lib/stdlib/doc/src/gen_statem.xml
index d50b88c561..bda3ef081d 100644
--- a/lib/stdlib/doc/src/gen_statem.xml
+++ b/lib/stdlib/doc/src/gen_statem.xml
@@ -803,12 +803,17 @@ ok
 	  </item>
 	  <tag><c>keep_state_and_data</c></tag>
 	  <item>
-	    The <c>gen_statem</c> will keep the current state, or
+	    The <c>gen_statem</c> will keep the current state or
 	    do a state transition to the current state if you like,
 	    keep the current server data,
 	    and execute all <c><anno>Actions</anno></c>
 	  </item>
 	</taglist>
+	<p>
+	  All these terms are tuples or atoms and this property
+	  will hold in any future version of <c>gen_statem</c>,
+	  just in case you need such a promise.
+	</p>
       </desc>
     </datatype>
   </datatypes>
diff --git a/lib/stdlib/src/gen_statem.erl b/lib/stdlib/src/gen_statem.erl
index e6ad7ab0be..16c296794f 100644
--- a/lib/stdlib/src/gen_statem.erl
+++ b/lib/stdlib/src/gen_statem.erl
@@ -135,32 +135,34 @@
 	 Caller :: caller(), Reply :: term()}.
 
 -type state_callback_result() ::
-    {'stop', % Stop the server
-     Reason :: term()} |
-    {'stop', % Stop the server
-     Reason :: term(),
-     NewData :: data()} |
-    {'stop_and_reply', % Reply then stop the server
-     Reason :: term(),
-     Replies :: [reply_action()] | reply_action()} |
-    {'stop_and_reply', % Reply then stop the server
-     Reason :: term(),
-     Replies :: [reply_action()] | reply_action(),
-     NewData :: data()} |
-    {'next_state', % {next_state,NewState,NewData,[]}
-     NewState :: state(),
-     NewData :: data()} |
-    {'next_state', % State transition, maybe to the same state
-     NewState :: state(),
-     NewData :: data(),
-     Actions :: [action()] | action()} |
-    {'keep_state', % {keep_state,NewData,[]}
-     NewData :: data()} |
-    {'keep_state', % Keep state, change data
-     NewData :: data(),
-     Actions :: [action()] | action()} |
-    {'keep_state_and_data', % Keep state and data -> only actions
-     Actions :: [action()] | action()}.
+	'stop' | % {stop,normal}
+	{'stop', % Stop the server
+	 Reason :: term()} |
+	{'stop', % Stop the server
+	 Reason :: term(),
+	 NewData :: data()} |
+	{'stop_and_reply', % Reply then stop the server
+	 Reason :: term(),
+	 Replies :: [reply_action()] | reply_action()} |
+	{'stop_and_reply', % Reply then stop the server
+	 Reason :: term(),
+	 Replies :: [reply_action()] | reply_action(),
+	 NewData :: data()} |
+	{'next_state', % {next_state,NewState,NewData,[]}
+	 NewState :: state(),
+	 NewData :: data()} |
+	{'next_state', % State transition, maybe to the same state
+	 NewState :: state(),
+	 NewData :: data(),
+	 Actions :: [action()] | action()} |
+	{'keep_state', % {keep_state,NewData,[]}
+	 NewData :: data()} |
+	{'keep_state', % Keep state, change data
+	 NewData :: data(),
+	 Actions :: [action()] | action()} |
+	'keep_state_and_data' | % {keep_state_and_data,[]}
+	{'keep_state_and_data', % Keep state and data -> only actions
+	 Actions :: [action()] | action()}.
 
 
 %% The state machine init function.  It is called only once and
@@ -841,6 +843,8 @@ loop_event_result(
   #{state := State, data := Data} = S,
   Events, Event, Result) ->
     case Result of
+	stop ->
+	    ?TERMINATE(exit, normal, Debug, S, [Event|Events]);
 	{stop,Reason} ->
 	    ?TERMINATE(exit, Reason, Debug, S, [Event|Events]);
 	{stop,Reason,NewData} ->
@@ -879,6 +883,10 @@ loop_event_result(
 	    loop_event_actions(
 	      Parent, Debug, S, Events, Event,
 	      State, State, NewData, Actions);
+	keep_state_and_data ->
+	    loop_event_actions(
+	      Parent, Debug, S, Events, Event,
+	      State, State, Data, []);
 	{keep_state_and_data,Actions} ->
 	    loop_event_actions(
 	      Parent, Debug, S, Events, Event,
diff --git a/lib/stdlib/test/gen_statem_SUITE.erl b/lib/stdlib/test/gen_statem_SUITE.erl
index f5cbdd9a40..09b309c36f 100644
--- a/lib/stdlib/test/gen_statem_SUITE.erl
+++ b/lib/stdlib/test/gen_statem_SUITE.erl
@@ -1233,7 +1233,7 @@ wfor_conf(Type, Content, Data) ->
 		    {next_state,idle,Data,
 		     [{reply,From,'eh?'}]};
 		_ ->
-		    throw({keep_state_and_data,[]})
+		    throw(keep_state_and_data)
 	    end;
 	Result ->
 	    Result
@@ -1334,7 +1334,7 @@ handle_common_events(cast, {get,Pid}, State, Data) ->
 handle_common_events({call,From}, stop, _, Data) ->
     {stop_and_reply,normal,[{reply,From,stopped}],Data};
 handle_common_events(cast, stop, _, _) ->
-    {stop,normal};
+    stop;
 handle_common_events({call,From}, {stop,Reason}, _, Data) ->
     {stop_and_reply,Reason,{reply,From,stopped},Data};
 handle_common_events(cast, {stop,Reason}, _, _) ->
-- 
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