protofsm: extend EmittedEvents with new Outbox field

go.mod

@@ -64,6 +64,8 @@ require (
 	pgregory.net/rapid v1.2.0
 )
 
+require github.com/lightningnetwork/lnd/actor v0.0.1-alpha
+
 require (
 	dario.cat/mergo v1.0.1 // indirect
 	github.com/Azure/go-ansiterm v0.0.0-20230124172434-306776ec8161 // indirect
@@ -213,6 +215,9 @@ replace github.com/gogo/protobuf => github.com/gogo/protobuf v1.3.2
 // allows us to specify that as an option.
 replace google.golang.org/protobuf => github.com/lightninglabs/protobuf-go-hex-display v1.33.0-hex-display
 
+// Use the local actor module for development.
+replace github.com/lightningnetwork/lnd/actor => ./actor
+
 // If you change this please also update docs/INSTALL.md and GO_VERSION in
 // Makefile (then run `make lint` to see where else it needs to be updated as
 // well).

protofsm/state_machine.go

@@ -42,6 +42,12 @@ type EmittedEvent[Event any] struct {
 	// ExternalEvent is an optional external event that is to be sent to
 	// the daemon for dispatch. Usually, this is some form of I/O.
 	ExternalEvents DaemonEventSet
+
+	// Outbox is an optional set of events that are accumulated during event
+	// processing and returned to the caller for processing into the main
+	// state machine. This enables nested state machines to emit events that
+	// bubble up to their parent.
+	Outbox []Event
 }
 
 // StateTransition is a state transition type. It denotes the next state to go