Fixed data race in store. Handle nils better

v2/internal/runtime/store.go

@@ -156,20 +156,26 @@ func (s *Store) resync() {
 	// Lock
 	s.mux.Lock()
 
-	// Stringify data
-	newdata, err := json.Marshal(s.data.Interface())
-	if err != nil {
-		if s.errorHandler != nil {
-			s.errorHandler(err)
-			return
+	var result string
+
+	if s.data.IsValid() {
+		rawdata, err := json.Marshal(s.data.Interface())
+		if err != nil {
+			if s.errorHandler != nil {
+				s.errorHandler(err)
+				return
+			}
 		}
+		result = string(rawdata)
+	} else {
+		result = "{}"
 	}
 
 	// Lock
 	s.mux.Unlock()
 
 	// Emit event to front end
-	s.runtime.Events.Emit("wails:sync:store:updatedbybackend:"+s.name, string(newdata))
+	s.runtime.Events.Emit("wails:sync:store:updatedbybackend:"+s.name, result)
 
 	// Notify subscribers
 	s.notify()
@@ -197,10 +203,16 @@ func (s *Store) notify() {
 // and notify listeners of the change
 func (s *Store) Set(data interface{}) error {
 
-	inType := reflect.TypeOf(data)
+	if data != nil {
+		inType := reflect.TypeOf(data)
 
-	if inType != s.dataType {
-		return fmt.Errorf("invalid data given in Store.Set(). Expected %s, got %s", s.dataType.String(), inType.String())
+		if inType != s.dataType && s.data.IsValid() {
+			return fmt.Errorf("invalid data given in Store.Set(). Expected %s, got %s", s.dataType.String(), inType.String())
+		}
+	}
+
+	if s.dataType == nil {
+		s.dataType = reflect.TypeOf(data)
 	}
 
 	// Save data
@@ -318,5 +330,12 @@ func (s *Store) Update(updater interface{}) {
 
 // Get returns the value of the data that's kept in the current state / Store
 func (s *Store) Get() interface{} {
+	s.mux.Lock()
+	defer s.mux.Unlock()
+
+	if !s.data.IsValid() {
+		return nil
+	}
+
 	return s.data.Interface()
 }

v2/internal/runtime/store_test.go

@@ -0,0 +1,166 @@
+package runtime
+
+import (
+	"context"
+	"math/rand"
+	"sync"
+	"testing"
+	"time"
+
+	internallogger "github.com/wailsapp/wails/v2/internal/logger"
+	"github.com/wailsapp/wails/v2/internal/servicebus"
+	"github.com/wailsapp/wails/v2/pkg/logger"
+
+	is2 "github.com/matryer/is"
+)
+
+func TestStoreProvider_NewWithNilDefault(t *testing.T) {
+	is := is2.New(t)
+
+	defaultLogger := logger.NewDefaultLogger()
+	testLogger := internallogger.New(defaultLogger)
+	//testLogger.SetLogLevel(logger.TRACE)
+	serviceBus := servicebus.New(testLogger)
+	err := serviceBus.Start()
+	is.NoErr(err)
+	defer serviceBus.Stop()
+
+	testRuntime := New(serviceBus)
+	storeProvider := newStore(testRuntime)
+
+	testStore := storeProvider.New("test", nil)
+	is.True(testStore.Get() == nil)
+
+	// You should be able to write a new value into a
+	// store initialised with nil
+	err = testStore.Set(100)
+	is.NoErr(err)
+
+	// You shouldn't be able to write different types to the
+	// store
+	err = testStore.Set(false)
+	is.True(err != nil)
+}
+
+func TestStoreProvider_NewWithScalarDefault(t *testing.T) {
+	is := is2.New(t)
+
+	defaultLogger := logger.NewDefaultLogger()
+	testLogger := internallogger.New(defaultLogger)
+	//testLogger.SetLogLevel(logger.TRACE)
+	serviceBus := servicebus.New(testLogger)
+	err := serviceBus.Start()
+	is.NoErr(err)
+	defer serviceBus.Stop()
+
+	testRuntime := New(serviceBus)
+	storeProvider := newStore(testRuntime)
+	testStore := storeProvider.New("test", 100)
+	value := testStore.Get()
+	is.Equal(value, 100)
+	testStore.resync()
+	value = testStore.Get()
+	is.Equal(value, 100)
+}
+
+func TestStoreProvider_NewWithStructDefault(t *testing.T) {
+	is := is2.New(t)
+
+	defaultLogger := logger.NewDefaultLogger()
+	testLogger := internallogger.New(defaultLogger)
+	//testLogger.SetLogLevel(logger.TRACE)
+	serviceBus := servicebus.New(testLogger)
+	err := serviceBus.Start()
+	is.NoErr(err)
+	defer serviceBus.Stop()
+
+	testRuntime := New(serviceBus)
+	storeProvider := newStore(testRuntime)
+
+	type TestValue struct {
+		Name string
+	}
+	testValue := &TestValue{
+		Name: "hi",
+	}
+
+	testStore := storeProvider.New("test", testValue)
+
+	err = testStore.Set(testValue)
+	is.NoErr(err)
+	testStore.resync()
+	value := testStore.Get()
+	is.Equal(value, testValue)
+	is.Equal(value.(*TestValue).Name, "hi")
+
+	testValue = &TestValue{
+		Name: "there",
+	}
+	err = testStore.Set(testValue)
+	is.NoErr(err)
+	testStore.resync()
+	value = testStore.Get()
+	is.Equal(value, testValue)
+	is.Equal(value.(*TestValue).Name, "there")
+
+}
+
+func TestStoreProvider_RapidReadWrite(t *testing.T) {
+	is := is2.New(t)
+
+	defaultLogger := logger.NewDefaultLogger()
+	testLogger := internallogger.New(defaultLogger)
+	//testLogger.SetLogLevel(logger.TRACE)
+	serviceBus := servicebus.New(testLogger)
+	err := serviceBus.Start()
+	is.NoErr(err)
+	defer serviceBus.Stop()
+
+	testRuntime := New(serviceBus)
+	storeProvider := newStore(testRuntime)
+
+	testStore := storeProvider.New("test", 1)
+
+	ctx, _ := context.WithTimeout(context.Background(), 3*time.Second)
+
+	var wg sync.WaitGroup
+	readers := 100
+	writers := 100
+	wg.Add(readers + writers)
+	// Setup readers
+	go func(testStore *Store, ctx context.Context) {
+		for readerCount := 0; readerCount < readers; readerCount++ {
+			go func(store *Store, ctx context.Context, id int) {
+				for {
+					select {
+					case <-ctx.Done():
+						wg.Done()
+						return
+					default:
+						store.Get()
+					}
+				}
+			}(testStore, ctx, readerCount)
+		}
+	}(testStore, ctx)
+
+	// Setup writers
+	go func(testStore *Store, ctx context.Context) {
+		for writerCount := 0; writerCount < writers; writerCount++ {
+			go func(store *Store, ctx context.Context, id int) {
+				for {
+					select {
+					case <-ctx.Done():
+						wg.Done()
+						return
+					default:
+						err := store.Set(rand.Int())
+						is.NoErr(err)
+					}
+				}
+			}(testStore, ctx, writerCount)
+		}
+	}(testStore, ctx)
+
+	wg.Wait()
+}