Generics

.github/workflows/main.yml

@@ -10,15 +10,15 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v5
 
       - name: Set up Go
-        uses: actions/setup-go@v2
+        uses: actions/setup-go@v5
         with:
-          go-version: 1.16
+          go-version: "1.24.x"
 
       - name: Test
-        run: go test -coverprofile=coverage.out ./...
+        run: make test
 
       - name: Convert coverage
         uses: jandelgado/gcov2lcov-action@v1.0.5

.gitignore

@@ -29,5 +29,6 @@ _testmain.go
 
 # Testing
 .coverprofile
+coverage.out
 
-.vscode
+.vscode

Makefile

@@ -2,7 +2,7 @@ default: services test
 
 .PHONY: test
 test:
-	go test ./...
+	CGO_ENABLED=1 go test -benchmem -bench=. -v ./... -race -coverprofile=coverage.out -covermode=atomic && go tool cover -func=coverage.out
 
 .PHONY: lint
 lint:

README.md

@@ -1,5 +1,5 @@
 [![PkgGoDev](https://pkg.go.dev/badge/github.com/looplab/fsm)](https://pkg.go.dev/github.com/looplab/fsm)
-![Bulid Status](https://github.com/looplab/fsm/actions/workflows/main.yml/badge.svg)
+![Build Status](https://github.com/looplab/fsm/actions/workflows/main.yml/badge.svg)
 [![Coverage Status](https://img.shields.io/coveralls/looplab/fsm.svg)](https://coveralls.io/r/looplab/fsm)
 [![Go Report Card](https://goreportcard.com/badge/looplab/fsm)](https://goreportcard.com/report/looplab/fsm)
 
@@ -24,17 +24,17 @@ package main
 
 import (
     "fmt"
-    "github.com/looplab/fsm"
+    "github.com/looplab/fsm/v2"
 )
 
 func main() {
-    fsm := fsm.NewFSM(
+    fsm := fsm.New[string, string](
         "closed",
-        fsm.Events{
+        fsm.Events[string, string]{
             {Name: "open", Src: []string{"closed"}, Dst: "open"},
             {Name: "close", Src: []string{"open"}, Dst: "closed"},
         },
-        fsm.Callbacks{},
+        fsm.Callbacks[string, string]{},
     )
 
     fmt.Println(fsm.Current())
@@ -64,7 +64,7 @@ package main
 
 import (
     "fmt"
-    "github.com/looplab/fsm"
+    "github.com/looplab/fsm/v2"
 )
 
 type Door struct {
@@ -77,14 +77,19 @@ func NewDoor(to string) *Door {
         To: to,
     }
 
-    d.FSM = fsm.NewFSM(
+    d.FSM = fsm.New[string, string](
         "closed",
-        fsm.Events{
+        fsm.Events[string, string]{
             {Name: "open", Src: []string{"closed"}, Dst: "open"},
             {Name: "close", Src: []string{"open"}, Dst: "closed"},
         },
-        fsm.Callbacks{
-            "enter_state": func(e *fsm.Event) { d.enterState(e) },
+        fsm.Callbacks[string, string]{
+            fsm.Callback[string, string]{
+                When: fsm.AfterAllStates,
+                F: func(cr *fsm.CallbackContext[MyEvent, MyState]) {
+                    d.enterState(e)
+                },
+            },
         },
     )
 

callback.go

@@ -0,0 +1,150 @@
+// Copyright (c) 2013 - Max Persson <max@looplab.se>
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package fsm
+
+import (
+	"cmp"
+	"fmt"
+)
+
+// CallbackType defines at which type of Event this callback should be called.
+type CallbackType string
+
+const (
+	// BeforeEvent called before event E
+	BeforeEvent = CallbackType("before_event")
+	// BeforeAllEvents called before all events
+	BeforeAllEvents = CallbackType("before_all_events")
+	// AfterEvent called after event E
+	AfterEvent = CallbackType("after_event")
+	// AfterAllEvents called after all events
+	AfterAllEvents = CallbackType("after_all_events")
+	// EnterState called after entering state S
+	EnterState = CallbackType("enter_state")
+	// EnterAllStates called after entering all states
+	EnterAllStates = CallbackType("enter_all_states")
+	// LeaveState is called before leaving state S.
+	LeaveState = CallbackType("leave_state")
+	// LeaveAllStates is called before leaving all states.
+	LeaveAllStates = CallbackType("leave_all_states")
+)
+
+// Callback defines a condition when the callback function F should be called in certain conditions.
+// The order of execution for CallbackTypes in the same event or state is:
+// The concrete CallbackType has precedence over a general one, e.g.
+// BeforeEvent E will be fired before BeforeAllEvents.
+type Callback[E cmp.Ordered, S cmp.Ordered] struct {
+	// When should the callback be called.
+	When CallbackType
+	// Event is the event that the callback should be called for. Only relevant for BeforeEvent and AfterEvent.
+	Event E
+	// State is the state that the callback should be called for. Only relevant for EnterState and LeaveState.
+	State S
+	// F is the callback function.
+	F func(*CallbackContext[E, S])
+}
+
+// Callbacks is a shorthand for defining the callbacks in New.
+type Callbacks[E cmp.Ordered, S cmp.Ordered] []Callback[E, S]
+
+// CallbackContext is the info that get passed as a reference in the callbacks.
+type CallbackContext[E cmp.Ordered, S cmp.Ordered] struct {
+	// FSM is an reference to the current FSM.
+	FSM *FSM[E, S]
+	// Event is the event name.
+	Event E
+	// Src is the state before the transition.
+	Src S
+	// Dst is the state after the transition.
+	Dst S
+	// Err is an optional error that can be returned from a callback.
+	Err error
+	// Args is an optional list of arguments passed to the callback.
+	Args []any
+	// canceled is an internal flag set if the transition is canceled.
+	canceled bool
+	// async is an internal flag set if the transition should be asynchronous
+	async bool
+}
+
+// Cancel can be called in before_<EVENT> or leave_<STATE> to cancel the
+// current transition before it happens. It takes an optional error, which will
+// overwrite e.Err if set before.
+func (ctx *CallbackContext[E, S]) Cancel(err ...error) {
+	ctx.canceled = true
+
+	if len(err) > 0 {
+		ctx.Err = err[0]
+	}
+}
+
+// Async can be called in leave_<STATE> to do an asynchronous state transition.
+//
+// The current state transition will be on hold in the old state until a final
+// call to Transition is made. This will complete the transition and possibly
+// call the other callbacks.
+func (ctx *CallbackContext[E, S]) Async() {
+	ctx.async = true
+}
+func (cs Callbacks[E, S]) validate() error {
+	for i := range cs {
+		cb := cs[i]
+		err := cb.validate()
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (c *Callback[E, S]) validate() error {
+	var (
+		zeroEvent E
+		zeroState S
+	)
+	switch c.When {
+	case BeforeEvent, AfterEvent:
+		if c.Event == zeroEvent {
+			return fmt.Errorf("%v given but no event", c.When)
+		}
+		if c.State != zeroState {
+			return fmt.Errorf("%v given but state %v specified", c.When, c.State)
+		}
+	case BeforeAllEvents, AfterAllEvents:
+		if c.Event != zeroEvent {
+			return fmt.Errorf("%v given with event %v", c.When, c.Event)
+		}
+		if c.State != zeroState {
+			return fmt.Errorf("%v given with state %v", c.When, c.State)
+		}
+	case EnterState, LeaveState:
+		if c.State == zeroState {
+			return fmt.Errorf("%v given but no state", c.When)
+		}
+		if c.Event != zeroEvent {
+			return fmt.Errorf("%v given but event %v specified", c.When, c.Event)
+		}
+	case EnterAllStates, LeaveAllStates:
+		if c.State != zeroState {
+			return fmt.Errorf("%v given with state %v", c.When, c.State)
+		}
+		if c.Event != zeroEvent {
+			return fmt.Errorf("%v given with event %v", c.When, c.Event)
+		}
+	default:
+		return fmt.Errorf("invalid callback:%v", c)
+	}
+	return nil
+}

callback_test.go

@@ -0,0 +1,62 @@
+package fsm
+
+import "testing"
+
+func TestCallbackValidate(t *testing.T) {
+	tests := []struct {
+		name      string
+		cb        Callback[string, string]
+		errString string
+	}{
+		{
+			name:      "before_event without event",
+			cb:        Callback[string, string]{When: BeforeEvent},
+			errString: "before_event given but no event",
+		},
+		{
+			name:      "before_event with state",
+			cb:        Callback[string, string]{When: BeforeEvent, Event: "open", State: "closed"},
+			errString: "before_event given but state closed specified",
+		},
+		{
+			name:      "before_event with state",
+			cb:        Callback[string, string]{When: BeforeAllEvents, Event: "open"},
+			errString: "before_all_events given with event open",
+		},
+
+		{
+			name:      "before_event without event",
+			cb:        Callback[string, string]{When: EnterState},
+			errString: "enter_state given but no state",
+		},
+		{
+			name:      "before_event with state",
+			cb:        Callback[string, string]{When: EnterState, Event: "open", State: "closed"},
+			errString: "enter_state given but event open specified",
+		},
+		{
+			name:      "before_event with state",
+			cb:        Callback[string, string]{When: EnterAllStates, State: "closed"},
+			errString: "enter_all_states given with state closed",
+		},
+	}
+
+	for i := range tests {
+		tt := tests[i]
+		t.Run(tt.name, func(t *testing.T) {
+			err := tt.cb.validate()
+
+			if tt.errString == "" && err != nil {
+				t.Errorf("err:%v", err)
+			}
+			if tt.errString != "" && err == nil {
+				t.Errorf("errstring:%s but err is nil", tt.errString)
+			}
+
+			if tt.errString != "" && err.Error() != tt.errString {
+				t.Errorf("transition failed %v", err)
+			}
+		})
+	}
+
+}

errors.go

@@ -14,15 +14,20 @@
 
 package fsm
 
+import (
+	"cmp"
+	"fmt"
+)
+
 // InvalidEventError is returned by FSM.Event() when the event cannot be called
 // in the current state.
-type InvalidEventError struct {
-	Event string
-	State string
+type InvalidEventError[E cmp.Ordered, S cmp.Ordered] struct {
+	Event E
+	State S
 }
 
-func (e InvalidEventError) Error() string {
-	return "event " + e.Event + " inappropriate in current state " + e.State
+func (e InvalidEventError[E, S]) Error() string {
+	return fmt.Sprintf("event %v inappropriate in current state %v", e.Event, e.State)
 }
 
 // UnknownEventError is returned by FSM.Event() when the event is not defined.
@@ -31,7 +36,7 @@ type UnknownEventError struct {
 }
 
 func (e UnknownEventError) Error() string {
-	return "event " + e.Event + " does not exist"
+	return fmt.Sprintf("event %s does not exist", e.Event)
 }
 
 // InTransitionError is returned by FSM.Event() when an asynchronous transition
@@ -41,7 +46,7 @@ type InTransitionError struct {
 }
 
 func (e InTransitionError) Error() string {
-	return "event " + e.Event + " inappropriate because previous transition did not complete"
+	return fmt.Sprintf("event %s inappropriate because previous transition did not complete", e.Event)
 }
 
 // NotInTransitionError is returned by FSM.Transition() when an asynchronous
@@ -60,7 +65,7 @@ type NoTransitionError struct {
 
 func (e NoTransitionError) Error() string {
 	if e.Err != nil {
-		return "no transition with error: " + e.Err.Error()
+		return fmt.Sprintf("no transition with error: %s", e.Err.Error())
 	}
 	return "no transition"
 }
@@ -73,7 +78,7 @@ type CanceledError struct {
 
 func (e CanceledError) Error() string {
 	if e.Err != nil {
-		return "transition canceled with error: " + e.Err.Error()
+		return fmt.Sprintf("transition canceled with error: %s", e.Err.Error())
 	}
 	return "transition canceled"
 }
@@ -86,7 +91,7 @@ type AsyncError struct {
 
 func (e AsyncError) Error() string {
 	if e.Err != nil {
-		return "async started with error: " + e.Err.Error()
+		return fmt.Sprintf("async started with error: %s", e.Err.Error())
 	}
 	return "async started"
 }

errors_test.go

@@ -22,7 +22,7 @@ import (
 func TestInvalidEventError(t *testing.T) {
 	event := "invalid event"
 	state := "state"
-	e := InvalidEventError{Event: event, State: state}
+	e := InvalidEventError[string, string]{Event: event, State: state}
 	if e.Error() != "event "+e.Event+" inappropriate in current state "+e.State {
 		t.Error("InvalidEventError string mismatch")
 	}