diff options
| -rw-r--r-- | lib/stdlib/doc/src/gen_statem.xml | 56 | ||||
| -rw-r--r-- | lib/stdlib/src/gen_statem.erl | 8 | ||||
| -rw-r--r-- | system/doc/design_principles/statem.xml | 5 |
3 files changed, 27 insertions, 42 deletions
diff --git a/lib/stdlib/doc/src/gen_statem.xml b/lib/stdlib/doc/src/gen_statem.xml index f18c1087ab..3322571b2c 100644 --- a/lib/stdlib/doc/src/gen_statem.xml +++ b/lib/stdlib/doc/src/gen_statem.xml @@ -119,9 +119,11 @@ erlang:'!' -----> Module:StateName/3 </p> <p> If a callback function fails or returns a bad value, - the <c>gen_statem</c> terminates. However, an exception of class + the <c>gen_statem</c> terminates, unless otherwise stated. + However, an exception of class <seealso marker="erts:erlang#throw/1"><c>throw</c></seealso> - is not regarded as an error but as a valid return. + is not regarded as an error but as a valid return + from all callback functions. </p> <marker id="state_function"/> <p> @@ -917,7 +919,8 @@ handle_event(_, _, State, Data) -> </p> <note> <p> - To avoid getting a late reply in the caller's + For <c><anno>Timeout</anno> =/= infinity</c>, + to avoid getting a late reply in the caller's inbox, this function spawns a proxy process that does the call. A late reply gets delivered to the dead proxy process, hence gets discarded. This is @@ -1288,12 +1291,6 @@ handle_event(_, _, State, Data) -> <seealso marker="#Module:code_change/4"><c>Module:code_change/4</c></seealso> returns. </p> - <p> - This function can use - <seealso marker="erts:erlang#throw/1"><c>erlang:throw/1</c></seealso> - to return <c>CallbackMode</c>, just for symmetry reasons. - There should be no actual reason to use this. - </p> <note> <p> If this function's body does not consist of solely one of two @@ -1368,11 +1365,6 @@ handle_event(_, _, State, Data) -> 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> - to return <c>Result</c> or <c>Reason</c>. - </p> </desc> </func> @@ -1432,11 +1424,6 @@ handle_event(_, _, State, Data) -> or <c>ignore</c>; see <seealso marker="#start_link/3"><c>start_link/3,4</c></seealso>. </p> - <p> - This function can use - <seealso marker="erts:erlang#throw/1"><c>erlang:throw/1</c></seealso> - to return <c>Result</c>. - </p> <note> <p> This callback is optional, so a callback module does not need @@ -1477,10 +1464,14 @@ handle_event(_, _, State, Data) -> This callback is optional, so a callback module does not need to export it. The <c>gen_statem</c> module provides a default implementation of this function that returns - <c>{State,Data}</c>. If this callback fails, the default - function returns <c>{State,Info}</c>, - where <c>Info</c> informs of the crash but no details, - to hide possibly sensitive data. + <c>{State,Data}</c>. + </p> + <p> + If this callback is exported but fails, + to hide possibly sensitive data, + the default function will instead return <c>{State,Info}</c>, + where <c>Info</c> says nothing but the fact that + <c>format_status/2</c> has crashed. </p> </note> <p>This function is called by a <c>gen_statem</c> process when @@ -1541,11 +1532,6 @@ handle_event(_, _, State, Data) -> printed in log files. Another use is to hide sensitive data from being written to the error log. </p> - <p> - This function can use - <seealso marker="erts:erlang#throw/1"><c>erlang:throw/1</c></seealso> - to return <c>Status</c>. - </p> </desc> </func> @@ -1620,9 +1606,12 @@ handle_event(_, _, State, Data) -> see <seealso marker="#type-action"><c>action()</c></seealso>. </p> <p> - These functions can use - <seealso marker="erts:erlang#throw/1"><c>erlang:throw/1</c></seealso>, - to return the result. + Note the fact that you can use + <seealso marker="erts:erlang#throw/1"><c>throw</c></seealso> + to return the result, which can be useful. + For example to bail out with <c>throw(keep_state_and_data)</c> + from deep within complex code that is in no position to + return <c>{next_state,State,Data}</c>. </p> </desc> </func> @@ -1695,11 +1684,6 @@ handle_event(_, _, State, Data) -> and an error report is issued using <seealso marker="kernel:error_logger#format/2"><c>error_logger:format/2</c></seealso>. </p> - <p> - This function can use - <seealso marker="erts:erlang#throw/1"><c>erlang:throw/1</c></seealso> - to return <c>Ignored</c>, which is ignored anyway. - </p> </desc> </func> </funcs> diff --git a/lib/stdlib/src/gen_statem.erl b/lib/stdlib/src/gen_statem.erl index 6d7b461ee3..a39503cb6b 100644 --- a/lib/stdlib/src/gen_statem.erl +++ b/lib/stdlib/src/gen_statem.erl @@ -1295,7 +1295,7 @@ format_status(Opt, PDict, #{module := Module}, State, Data) -> _:_ -> format_status_default( Opt, State, - "Module:format_status/2 crashed") + atom_to_list(Module) ++ ":format_status/2 crashed") end; false -> format_status_default(Opt, State, Data) @@ -1303,10 +1303,10 @@ format_status(Opt, PDict, #{module := Module}, State, Data) -> %% The default Module:format_status/2 format_status_default(Opt, State, Data) -> - SSD = {State,Data}, + StateData = {State,Data}, case Opt of terminate -> - SSD; + StateData; _ -> - [{data,[{"State",SSD}]}] + [{data,[{"State",StateData}]}] end. diff --git a/system/doc/design_principles/statem.xml b/system/doc/design_principles/statem.xml index 1351997bc1..f785ca9650 100644 --- a/system/doc/design_principles/statem.xml +++ b/system/doc/design_principles/statem.xml @@ -608,7 +608,7 @@ init(Args) -> callback function <c>terminate(shutdown, State, Data)</c>. </p> <p> - In the following example, function <c>terminate/3</c> + In this example, function <c>terminate/3</c> locks the door if it is open, so we do not accidentally leave the door open when the supervision tree terminates: </p> @@ -1217,7 +1217,8 @@ format_status(Opt, [_PDict,State,Data]) -> <seealso marker="stdlib:gen_statem#Module:format_status/2"><c>Module:format_status/2</c></seealso> function. If you do not, a default implementation is used that does the same as this example function without filtering - the <c>Data</c> term, that is, <c>StateData = {State,Data}</c>. + the <c>Data</c> term, that is, <c>StateData = {State,Data}</c>, + in this example containing sensitive information. </p> </section> |