Fix getGarbageLen to retrun correct size

pkg/document/crdt/root.go

@@ -151,19 +151,22 @@ func (r *Root) RemovedElementLen() int {
 // GarbageLen returns the count of removed elements.
 func (r *Root) GarbageLen() int {
 	count := 0
+	seen := make(map[string]bool)
 
 	for _, pair := range r.removedElementPairMapByCreatedAt {
-		count++
+		seen[pair.elem.CreatedAt().ToTestString()] = true
 
 		switch elem := pair.elem.(type) {
 		case Container:
 			elem.Descendants(func(elem Element, parent Container) bool {
-				count++
+				seen[elem.CreatedAt().ToTestString()] = true
 				return false
 			})
 		}
 	}
 
+	count += len(seen)
+
 	for _, element := range r.elementHasRemovedNodesSetByCreatedAt {
 		count += element.removedNodesLen()
 	}

test/integration/gc_test.go

@@ -382,4 +382,52 @@ func TestGarbageCollection(t *testing.T) {
 		assert.Equal(t, 0, d1.GarbageLen())
 		assert.Equal(t, 6, d2.GarbageLen())
 	})
+
+	t.Run("GarbageLen should return the actual number of elements garbage-collected", func(t *testing.T) {
+		ctx := context.Background()
+		docKey := helper.TestDocKey(t)
+		d1 := document.New(docKey)
+		d2 := document.New(docKey)
+
+		err := c1.Attach(ctx, d1)
+		assert.NoError(t, err)
+
+		err = d1.Update(func(root *json.Object, p *presence.Presence) error {
+			root.SetNewObject("point").
+				SetInteger("point.x", 0).
+				SetInteger("point.y", 0)
+			return nil
+		})
+		err = c1.Sync(ctx)
+		assert.NoError(t, err)
+		err = c2.Attach(ctx, d2)
+		assert.NoError(t, err)
+
+		err = d1.Update(func(root *json.Object, p *presence.Presence) error {
+			root.Delete("point")
+			return nil
+		})
+		assert.NoError(t, err)
+		assert.Equal(t, 3, d1.GarbageLen())
+
+		err = d2.Update(func(root *json.Object, p *presence.Presence) error {
+			root.GetObject("point").Delete("point.x")
+			return nil
+		})
+		assert.NoError(t, err)
+		assert.Equal(t, 1, d2.GarbageLen())
+
+		err = c1.Sync(ctx)
+		assert.NoError(t, err)
+		err = c2.Sync(ctx)
+		assert.NoError(t, err)
+		err = c1.Sync(ctx)
+		assert.NoError(t, err)
+
+		assert.Equal(t, 3, d1.GarbageLen())
+		assert.Equal(t, 3, d2.GarbageLen())
+
+		assert.Equal(t, d1.GarbageCollect(time.MaxTicket), 3)
+		assert.Equal(t, d2.GarbageCollect(time.MaxTicket), 3)
+	})
 }