Propagate origin event through completion transitions

Author: gabewillen

include/boost/sml.hpp

@@ -1065,6 +1065,8 @@ struct anonymous : internal_event {
 template <class TEvent>
 struct completion : internal_event {
   constexpr static auto c_str() { return "completion"; }
+  constexpr explicit completion(const TEvent &event) : event_(event) {}
+  const TEvent &event_;
 };
 template <class T, class TEvent = T>
 struct on_entry : internal_event, entry_exit {
@@ -1125,6 +1127,26 @@ template <class TEvent>
 using get_generic_t = typename event_type<TEvent>::generic_t;
 template <class TEvent>
 using get_mapped_t = typename event_type<TEvent>::mapped_t;
+template <class TEvent>
+constexpr const TEvent &get_origin_event(const TEvent &event) {
+  return event;
+}
+template <class T, class TEvent>
+constexpr const TEvent &get_origin_event(const unexpected_event<T, TEvent> &event) {
+  return event.event_;
+}
+template <class T, class TEvent>
+constexpr const TEvent &get_origin_event(const on_entry<T, TEvent> &event) {
+  return event.event_;
+}
+template <class T, class TEvent>
+constexpr const TEvent &get_origin_event(const on_exit<T, TEvent> &event) {
+  return event.event_;
+}
+template <class T, class TException>
+constexpr const TException &get_origin_event(const exception<T, TException> &event) {
+  return event.exception_;
+}
 template <class... TEvents>
 struct process : queue_handler<TEvents...> {
   using queue_handler<TEvents...>::queue_handler;
@@ -1860,28 +1882,28 @@ struct sm_impl : aux::conditional_t<aux::should_not_subclass_statemachine_class<
     return handled && queued_handled;
   }
   template <class TOriginEvent, class TDeps, class TSubs>
-  constexpr bool process_completion_event(TDeps &deps, TSubs &subs, aux::true_type) {
-    return process_internal_events(completion<TOriginEvent>{}, deps, subs);
+  constexpr bool process_completion_event(const TOriginEvent &event, TDeps &deps, TSubs &subs, aux::true_type) {
+    return process_internal_events(completion<TOriginEvent>{event}, deps, subs);
   }
   template <class TOriginEvent, class TDeps, class TSubs>
-  constexpr bool process_completion_event(TDeps &, TSubs &, aux::false_type) {
+  constexpr bool process_completion_event(const TOriginEvent &, TDeps &, TSubs &, aux::false_type) {
     return false;
   }
   template <class TOriginEvent, class TDeps, class TSubs>
-  constexpr bool process_post_event_step(TDeps &deps, TSubs &subs) {
+  constexpr bool process_post_event_step(const TOriginEvent &event, TDeps &deps, TSubs &subs) {
     return process_completion_event<TOriginEvent>(
-               deps, subs, typename aux::is_base_of<completion<TOriginEvent>, events_ids_t>::type{}) ||
+               event, deps, subs, typename aux::is_base_of<completion<TOriginEvent>, events_ids_t>::type{}) ||
            process_internal_events(anonymous{}, deps, subs);
   }
   template <class TOriginEvent, class TDeps, class TSubs>
-  constexpr void process_post_events(TDeps &deps, TSubs &subs) {
-    while (process_post_event_step<TOriginEvent>(deps, subs)) {
+  constexpr void process_post_events(const TOriginEvent &event, TDeps &deps, TSubs &subs) {
+    while (process_post_event_step<TOriginEvent>(event, deps, subs)) {
     }
   }
   template <class TOriginEvent, class TEvent, class TDeps, class TSubs>
   constexpr bool process_event_and_post_events(const TEvent &event, TDeps &deps, TSubs &subs) {
     const bool handled = process_internal_events(event, deps, subs);
-    process_post_events<TOriginEvent>(deps, subs);
+    process_post_events<TOriginEvent>(get_origin_event(event), deps, subs);
     return handled;
   }
   constexpr void initialize(const aux::type_list<> &) {}
@@ -2351,6 +2373,14 @@ template <class T, class TEvent, class Tsm, class TDeps>
 constexpr decltype(auto) get_arg(const aux::type_wrapper<const TEvent &> &, const back::on_exit<T, TEvent> &event, Tsm &, TDeps &) {
   return event.event_;
 }
+template <class TEvent, class Tsm, class TDeps>
+constexpr decltype(auto) get_arg(const aux::type_wrapper<const TEvent &> &, const back::completion<TEvent> &event, Tsm &, TDeps &) {
+  return event.event_;
+}
+template <class TEvent, class Tsm, class TDeps>
+constexpr decltype(auto) get_arg(const aux::type_wrapper<TEvent> &, const back::completion<TEvent> &event, Tsm &, TDeps &) {
+  return event.event_;
+}
 template <class T, class TEvent, class Tsm, class TDeps>
 constexpr decltype(auto) get_arg(const aux::type_wrapper<const TEvent &> &, const back::exception<T, TEvent> &event, Tsm &, TDeps &) {
   return event.exception_;
@@ -2756,6 +2786,18 @@ struct ignore<E, aux::type_list<Ts...>> {
   };
   using type = aux::join_t<typename non_events<Ts>::type...>;
 };
+template <class TEvent, class... Ts>
+struct ignore<back::completion<TEvent>, aux::type_list<Ts...>> {
+  template <class T>
+  struct non_events {
+    using arg_t = aux::remove_const_t<aux::remove_reference_t<T>>;
+    using type = aux::conditional_t<aux::is_same<TEvent, arg_t>::value ||
+                                        aux::is_same<back::completion<TEvent>, arg_t>::value ||
+                                        aux::is_same<T, action_base>::value,
+                                    aux::type_list<>, aux::type_list<T>>;
+  };
+  using type = aux::join_t<typename non_events<Ts>::type...>;
+};
 template <class T, class E, class = void>
 struct get_deps {
   using type = typename ignore<E, args_t<T, E>>::type;

test/ft/actions_process_n_defer.cpp

@@ -120,7 +120,9 @@ test process_n_defer_again = [] {
 
 test process_queue_runs_completion_for_popped_event_type = [] {
   struct trigger {};
-  struct queued1 {};
+  struct queued1 {
+    int value{};
+  };
   struct queued2 {};
   struct q0 {};
   struct q1 {};
@@ -140,9 +142,9 @@ test process_queue_runs_completion_for_popped_event_type = [] {
       auto wrong_state = state<wrong>;
       // clang-format off
       return make_transition_table(
-        *q0_state + event<trigger> / (process(queued1{}), process(queued2{})) = q1_state
+        *q0_state + event<trigger> / (process(queued1{42}), process(queued2{})) = q1_state
         , q1_state + event<queued1> = q2_state
-        , q2_state + completion<queued1> = q3_state
+        , q2_state + completion<queued1>[([](const queued1& event) { return event.value == 42; })] = q3_state
         , q2_state + event<queued2> = wrong_state
         , q3_state + event<queued2> = done_state
       );
@@ -157,7 +159,9 @@ test process_queue_runs_completion_for_popped_event_type = [] {
 };
 
 test defer_queue_runs_completion_for_popped_event_type = [] {
-  struct deferred {};
+  struct deferred {
+    int value{};
+  };
   struct release {};
   struct d0 {};
   struct d1 {};
@@ -178,15 +182,15 @@ test defer_queue_runs_completion_for_popped_event_type = [] {
         *d0_state + event<deferred> / defer
         , d0_state + event<release> = d1_state
         , d1_state + event<deferred> = d2_state
-        , d2_state + completion<deferred> = done_state
+        , d2_state + completion<deferred>[([](const deferred& event) { return event.value == 11; })] = done_state
         , d2_state + completion<release> = wrong_state
       );
       // clang-format on
     }
   };
 
   sml::sm<c, sml::process_queue<std::queue>, sml::defer_queue<std::deque>> sm{};
-  expect(sm.process_event(deferred{}));
+  expect(sm.process_event(deferred{11}));
   expect(sm.process_event(release{}));
   expect(sm.is(sml::state<done>));
   expect(!sm.is(sml::state<wrong>));

test/ft/transitions.cpp

@@ -89,13 +89,17 @@ test anonymous_transition = [] {
 };
 
 test completion_transition_runs_before_anonymous = [] {
+  struct payload {
+    int value{};
+  };
+
   struct c {
     auto operator()() noexcept {
       using namespace sml;
       // clang-format off
       return make_transition_table(
-         *idle + event<e1> = s1
-        ,s1 + completion<e1> / [this] { calls += "completion|"; } = s2
+         *idle + event<payload> = s1
+        ,s1 + completion<payload> / [this](const payload& event) { calls += "completion(" + std::to_string(event.value) + ")|"; } = s2
         ,s1 / [this] { calls += "anonymous_s1|"; } = s3
         ,s2 / [this] { calls += "anonymous_s2|"; } = s4
       );
@@ -106,10 +110,10 @@ test completion_transition_runs_before_anonymous = [] {
   };
 
   sml::sm<c> sm{};
-  expect(sm.process_event(e1{}));
+  expect(sm.process_event(payload{42}));
   expect(sm.is(s4));
   expect(!sm.is(s3));
-  expect(static_cast<const c&>(sm).calls == "completion|anonymous_s2|");
+  expect(static_cast<const c&>(sm).calls == "completion(42)|anonymous_s2|");
 };
 
 test subsequent_anonymous_transitions = [] {