Reintroduce execution block

Demo/Sources/Demo/StateMachineExamples.swift

@@ -104,6 +104,8 @@ class StateMachineExamples {
         try await stateMachine.process(event: .start)
         try await stateMachine.process(event: .stop)
         try await stateMachine.process(event: .start)
-        try await stateMachine.process(event: .execute)
+        try await stateMachine.process(event: .execute) {
+            print("Execution block called.")
+        }
     }
 }

Framework/Sources/StateMachine.swift

@@ -28,7 +28,7 @@ public actor StateMachine<State: Hashable & Sendable, Event: Hashable & Sendable
         }
     }
 
-    public func process(event: Event) throws {
+    public func process(event: Event, execution: ExecutionBlock? = nil) async throws {
         let transitions = transitionsByEvent[event]
         let performableTransitions = transitions?.filter { $0.source == currentState } ?? []
 
@@ -41,15 +41,17 @@ public actor StateMachine<State: Hashable & Sendable, Event: Hashable & Sendable
         let transition = performableTransitions.first!
 
         log(message: "Processing event '\(event)' from '\(currentState)'")
-        transition.executePreBlock()
+        try await transition.executePreBlock()
 
         log(message: "Processed pre condition for event '\(event)' from '\(transition.source)' to '\(transition.destination)'")
 
+        try await execution?()
+
         let previousState = currentState
         currentState = transition.destination
 
         log(message: "Processed state change from '\(previousState)' to '\(transition.destination)'")
-        transition.executePostBlock()
+        try await transition.executePostBlock()
 
         log(message: "Processed post condition for event '\(event)' from '\(transition.source)' to '\(transition.destination)'")
     }

Framework/Sources/Transition.swift

@@ -2,7 +2,7 @@
 
 import Foundation
 
-public typealias ExecutionBlock = @Sendable () -> Void
+public typealias ExecutionBlock = @Sendable () async throws -> Void
 
 public struct Transition<State: Sendable, Event: Sendable>: Sendable {
 
@@ -24,11 +24,11 @@ public struct Transition<State: Sendable, Event: Sendable>: Sendable {
         self.postBlock = postBlock
     }
 
-    func executePreBlock() {
-        preBlock?()
+    func executePreBlock() async throws {
+        try await preBlock?()
     }
 
-    func executePostBlock() {
-        postBlock?()
+    func executePostBlock() async throws {
+        try await postBlock?()
     }
 }

README.md

@@ -68,6 +68,10 @@ do {
 } catch {
     print("Event 'pause' cannot currently be processed.")
 }
+
+try await stateMachine.process(event: .start) {
+    print("Execution block called.")
+}
 ```
 
 ### Logging

Tests/Sources/TransitionTests.swift

@@ -15,16 +15,16 @@ struct TransitionTests {
         #expect(transition.destination == to)
     }
 
-    @Test func callback() async {
-        await confirmation("preBlock called") { preConfirmation in
-            await confirmation("postBlock called") { postConfirmation in
+    @Test func callback() async throws {
+        try await confirmation("preBlock called") { preConfirmation in
+            try await confirmation("postBlock called") { postConfirmation in
                 let transition = Transition(with: "event", from: "from", to: "to", preBlock: {
                     preConfirmation()
                 }, postBlock: {
                     postConfirmation()
                 })
-                transition.executePreBlock()
-                transition.executePostBlock()
+                try await transition.executePreBlock()
+                try await transition.executePostBlock()
             }
         }
     }