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-rw-r--r--lib/stdlib/doc/src/gen_statem.xml18
-rw-r--r--lib/stdlib/src/gen_statem.erl13
2 files changed, 20 insertions, 11 deletions
diff --git a/lib/stdlib/doc/src/gen_statem.xml b/lib/stdlib/doc/src/gen_statem.xml
index c57a31fa21..ed44eef912 100644
--- a/lib/stdlib/doc/src/gen_statem.xml
+++ b/lib/stdlib/doc/src/gen_statem.xml
@@ -1262,9 +1262,9 @@ handle_event(_, _, State, Data) ->
<v>&nbsp;&nbsp;Vsn = term()</v>
<v>OldState = NewState = term()</v>
<v>Extra = term()</v>
- <v>Result = {NewCallbackMode,NewState,NewData} | Reason</v>
+ <v>Result = {CallbackMode,NewState,NewData} | Reason</v>
<v>
- NewCallbackMode =
+ CallbackMode =
<seealso marker="#type-callback_mode">callback_mode()</seealso>
</v>
<v>
@@ -1321,11 +1321,19 @@ handle_event(_, _, State, Data) ->
<p>
If successful, the function must return the updated
internal state in an
- <c>{NewCallbackMode,NewState,NewData}</c> tuple.
+ <c>{CallbackMode,NewState,NewData}</c> tuple.
</p>
<p>
- If the function returns <c>Reason</c>, the ongoing
- upgrade fails and rolls back to the old release.</p>
+ If the function returns a failure <c>Reason</c>, the ongoing
+ upgrade fails and rolls back to the old release.
+ Note that <c>Reason</c> can not be a 3-tuple since that
+ will be regarded as a
+ <c>{CallbackMode,NewState,NewData}</c> tuple,
+ and that a tuple matching <c>{ok,_}</c>
+ is an invalid failure <c>Reason</c>.
+ It is recommended to use an atom as <c>Reason</c> since
+ it will be wrapped in an <c>{error,Reason}</c> tuple.
+ </p>
<p>
This function can use
<seealso marker="erts:erlang#throw/1"><c>erlang:throw/1</c></seealso>
diff --git a/lib/stdlib/src/gen_statem.erl b/lib/stdlib/src/gen_statem.erl
index 23bddafeed..c02e6a1a19 100644
--- a/lib/stdlib/src/gen_statem.erl
+++ b/lib/stdlib/src/gen_statem.erl
@@ -219,9 +219,10 @@
OldState :: state(),
OldData :: data(),
Extra :: term()) ->
- {NewCallbackMode :: callback_mode(),
+ {CallbackMode :: callback_mode(),
NewState :: state(),
- NewData :: data()}.
+ NewData :: data()} |
+ (Reason :: term()).
%% Format the callback module state in some sensible that is
%% often condensed way. For StatusOption =:= 'normal' the perferred
@@ -630,11 +631,11 @@ system_code_change(
Result -> Result
end
of
- {NewCallbackMode,NewState,NewData} ->
- callback_mode(NewCallbackMode) orelse
- error({callback_mode,NewCallbackMode}),
+ {CallbackMode,NewState,NewData} ->
+ callback_mode(CallbackMode) orelse
+ error({callback_mode,CallbackMode}),
{ok,
- S#{callback_mode := NewCallbackMode,
+ S#{callback_mode := CallbackMode,
state := NewState,
data := NewData}};
{ok,_} = Error ->