Refuse to subscribe to document type for broadcasting

api/types/event.go

@@ -9,7 +9,8 @@ type DocEvent struct {
 	DocumentID ID
 }
 
-// BroadcastEvent represents events that are delievered to subscribers.
+// BroadcastEvent represents events that are delievered to broadcast
+// event subscribers.
 type BroadcastEvent struct {
 	Type      string
 	Publisher *time.ActorID

pkg/document/document.go

@@ -19,6 +19,7 @@ package document
 
 import (
 	gojson "encoding/json"
+	"errors"
 	"fmt"
 
 	"github.com/yorkie-team/yorkie/pkg/document/change"
@@ -30,6 +31,12 @@ import (
 	"github.com/yorkie-team/yorkie/pkg/document/time"
 )
 
+var (
+	// ErrReservedEventType is returned when the event type is "document".
+	ErrReservedEventType = errors.New(
+		"the \"document\" event type is reserved for document events")
+)
+
 // DocEvent represents the event that occurred in the document.
 type DocEvent struct {
 	Type      DocEventType
@@ -377,6 +384,10 @@ func (d *Document) BroadcastRequests() <-chan BroadcastRequest {
 
 // Broadcast encodes the payload and makes a "Broadcast" type request.
 func (d *Document) Broadcast(eventType string, payload any) error {
+	if eventType == "document" {
+		return ErrReservedEventType
+	}
+
 	marshaled, err := gojson.Marshal(payload)
 	if err != nil {
 		return fmt.Errorf("marshal payload in broadcast event: %w", err)
@@ -395,26 +406,36 @@ func (d *Document) Broadcast(eventType string, payload any) error {
 func (d *Document) SubscribeBroadcastEvent(
 	eventType string,
 	handler func(eventType, publisher string, payload []byte) error,
-) {
+) error {
+	if eventType == "document" {
+		return ErrReservedEventType
+	}
+
 	d.broadcastEventHandlers[eventType] = handler
 
 	d.broadcastRequests <- BroadcastRequest{
 		RequestType: Subscribe,
 		EventType:   eventType,
 	}
+	return nil
 }
 
 // UnsubscribeBroadcastEvent deregisters the event handler and makes
 // a "Unsubscribe" type request.
 func (d *Document) UnsubscribeBroadcastEvent(
 	eventType string,
-) {
+) error {
+	if eventType == "document" {
+		return ErrReservedEventType
+	}
+
 	delete(d.broadcastEventHandlers, eventType)
 
 	d.broadcastRequests <- BroadcastRequest{
 		RequestType: Unsubscribe,
 		EventType:   eventType,
 	}
+	return nil
 }
 
 // BroadcastEventHandlers returns registered event handlers for events.

test/integration/document_test.go

@@ -435,13 +435,15 @@ func TestDocument(t *testing.T) {
 		assert.NoError(t, c1.Attach(ctx, d1))
 		rch1, err := c1.Watch(ctx, d1)
 		assert.NoError(t, err)
-		d1.SubscribeBroadcastEvent("mention", handler)
+		err = d1.SubscribeBroadcastEvent("mention", handler)
+		assert.NoError(t, err)
 
 		d2 := document.New(helper.TestDocKey(t))
 		assert.NoError(t, c2.Attach(ctx, d2))
 		rch2, err := c2.Watch(ctx, d2)
 		assert.NoError(t, err)
-		d2.SubscribeBroadcastEvent("mention", handler)
+		err = d2.SubscribeBroadcastEvent("mention", handler)
+		assert.NoError(t, err)
 
 		err = d2.Broadcast("mention", "yorkie")
 		assert.NoError(t, err)
@@ -472,6 +474,7 @@ func TestDocument(t *testing.T) {
 
 	// TODO(sejongk): broadcast to multiple subscribers
 	// TODO(sejongk): dont broadcast to unsubscribers
+	// TODO(sejongk): reject subscribing document for broadcast
 }
 
 func TestDocumentWithProjects(t *testing.T) {