add async closer

async/result.go

@@ -60,6 +60,10 @@ type ResultHandler[E any] func(ctx context.Context, entry E, cause error)
 
 var DiscardVoidHandler ResultHandler[Void] = func(_ context.Context, _ Void, _ error) {}
 
+type Closer interface {
+	Close() (future Future[Void])
+}
+
 func tryCloseResultWhenUnexpectedlyErrorOccur(v any) {
 	if v == nil {
 		return
@@ -68,6 +72,12 @@ func tryCloseResultWhenUnexpectedlyErrorOccur(v any) {
 	closer, isCloser := ri.(io.Closer)
 	if isCloser {
 		_ = closer.Close()
+		return
+	}
+	asyncCloser, isAsyncCloser := ri.(Closer)
+	if isAsyncCloser {
+		asyncCloser.Close().OnComplete(DiscardVoidHandler)
+		return
 	}
 }
 

async/stream_test.go

@@ -16,6 +16,17 @@ func (c *Closer) Close() error {
 	return nil
 }
 
+type AsyncCloser struct {
+	N   int
+	t   *testing.T
+	ctx context.Context
+}
+
+func (c *AsyncCloser) Close() async.Future[async.Void] {
+	c.t.Log("close ", c.N)
+	return async.SucceedImmediately[async.Void](c.ctx, async.Void{})
+}
+
 func TestTryStreamPromise(t *testing.T) {
 	ctx, closer := prepare()
 	defer func() {
@@ -47,6 +58,37 @@ func TestTryStreamPromise(t *testing.T) {
 	}
 }
 
+func TestTryStreamPromiseWithAsyncCloser(t *testing.T) {
+	ctx, closer := prepare()
+	defer func() {
+		err := closer()
+		if err != nil {
+			t.Error(err)
+		}
+	}()
+	promise, promiseErr := async.Make[*AsyncCloser](ctx, async.WithStream())
+	if promiseErr != nil {
+		t.Errorf("try promise failed")
+		return
+	}
+	future := promise.Future()
+	future.OnComplete(func(ctx context.Context, result *AsyncCloser, err error) {
+		t.Log("future entry:", result, err)
+		if err != nil {
+			t.Log("is eof:", async.IsEOF(err))
+			return
+		}
+		return
+	})
+	for i := 0; i < 10; i++ {
+		promise.Succeed(&AsyncCloser{N: i, t: t, ctx: ctx})
+	}
+	promise.Cancel()
+	for i := 0; i < 10; i++ {
+		promise.Succeed(&AsyncCloser{N: i, t: t, ctx: ctx})
+	}
+}
+
 func TestMustStreamPromise(t *testing.T) {
 	ctx, closer := prepare()
 	defer func() {