Add msgIDGenerator to abstract away id

This will avoid accidental use of id when newID should be used.

Resolves: #984 (comment)

Author: ankur22

common/connection.go

@@ -33,14 +33,20 @@ var _ cdp.Executor = &Connection{}
 // chrome, it's best to work with unique ids to avoid the Execute
 // handlers working with the wrong response, or handlers deadlocking
 // when their response is rerouted to the wrong handler.
+//
+// Use the msgIDGenerator interface to abstract `id` away.
 type msgID struct {
 	id int64
 }
 
-func (m *msgID) new() int64 {
+func (m *msgID) newID() int64 {
 	return atomic.AddInt64(&m.id, 1)
 }
 
+type msgIDGenerator interface {
+	newID() int64
+}
+
 type executorEmitter interface {
 	cdp.Executor
 	EventEmitter
@@ -125,7 +131,7 @@ type Connection struct {
 	done         chan struct{}
 	closing      chan struct{}
 	shutdownOnce sync.Once
-	msgID        *msgID
+	msgIDGen     msgIDGenerator
 
 	sessionsMu sync.RWMutex
 	sessions   map[target.SessionID]*Session
@@ -163,7 +169,7 @@ func NewConnection(ctx context.Context, wsURL string, logger *log.Logger) (*Conn
 		errorCh:          make(chan error),
 		done:             make(chan struct{}),
 		closing:          make(chan struct{}),
-		msgID:            &msgID{},
+		msgIDGen:         &msgID{},
 		sessions:         make(map[target.SessionID]*Session),
 	}
 
@@ -329,7 +335,7 @@ func (c *Connection) recvLoop() {
 			sid, tid := eva.SessionID, eva.TargetInfo.TargetID
 
 			c.sessionsMu.Lock()
-			session := NewSession(c.ctx, c, sid, tid, c.logger, c.msgID)
+			session := NewSession(c.ctx, c, sid, tid, c.logger, c.msgIDGen)
 			c.logger.Debugf("Connection:recvLoop:EventAttachedToTarget", "sid:%v tid:%v wsURL:%q", sid, tid, c.wsURL)
 			c.sessions[sid] = session
 			c.sessionsMu.Unlock()
@@ -509,7 +515,7 @@ func (c *Connection) Close(args ...goja.Value) {
 // Execute implements cdproto.Executor and performs a synchronous send and receive.
 func (c *Connection) Execute(ctx context.Context, method string, params easyjson.Marshaler, res easyjson.Unmarshaler) error {
 	c.logger.Debugf("connection:Execute", "wsURL:%q method:%q", c.wsURL, method)
-	id := c.msgID.new()
+	id := c.msgIDGen.newID()
 
 	// Setup event handler used to block for response to message being sent.
 	ch := make(chan *cdproto.Message, 1)

common/session.go

@@ -23,7 +23,7 @@ type Session struct {
 	conn     *Connection
 	id       target.SessionID
 	targetID target.ID
-	msgID    *msgID
+	msgIDGen msgIDGenerator
 	readCh   chan *cdproto.Message
 	done     chan struct{}
 	closed   bool
@@ -34,7 +34,7 @@ type Session struct {
 
 // NewSession creates a new session.
 func NewSession(
-	ctx context.Context, conn *Connection, id target.SessionID, tid target.ID, logger *log.Logger, msgID *msgID,
+	ctx context.Context, conn *Connection, id target.SessionID, tid target.ID, logger *log.Logger, msgIDGen msgIDGenerator,
 ) *Session {
 	s := Session{
 		BaseEventEmitter: NewBaseEventEmitter(ctx),
@@ -43,7 +43,7 @@ func NewSession(
 		targetID:         tid,
 		readCh:           make(chan *cdproto.Message),
 		done:             make(chan struct{}),
-		msgID:            msgID,
+		msgIDGen:         msgIDGen,
 
 		logger: logger,
 	}
@@ -118,7 +118,7 @@ func (s *Session) Execute(ctx context.Context, method string, params easyjson.Ma
 		return ErrTargetCrashed
 	}
 
-	id := s.msgID.new()
+	id := s.msgIDGen.newID()
 
 	// Setup event handler used to block for response to message being sent.
 	ch := make(chan *cdproto.Message, 1)
@@ -186,7 +186,7 @@ func (s *Session) ExecuteWithoutExpectationOnReply(ctx context.Context, method s
 		}
 	}
 	msg := &cdproto.Message{
-		ID: s.msgID.new(),
+		ID: s.msgIDGen.newID(),
 		// We use different sessions to send messages to "targets"
 		// (browser, page, frame etc.) in CDP.
 		//