route all communication via the browser

Use a single websocket connection per browser, removing the need for an
extra websocket connection per target.

This is thanks to the Target.sendMessageToTarget command to send
messages to each target, and the Target.receivedMessageFromTarget event
to receive messages back.

The browser handles activity via a single worker goroutine, and the same
technique is used for each target. This means that commands and events
are dealt with in order, and we can do away with some complexity like
mutexes and extra go statements.

actions.go

@@ -49,7 +49,6 @@ func Sleep(d time.Duration) Action {
 	return ActionFunc(func(ctxt context.Context, h cdp.Executor) error {
 		select {
 		case <-time.After(d):
-
 		case <-ctxt.Done():
 			return ctxt.Err()
 		}

allocate.go

@@ -136,11 +136,12 @@ func (p *ExecAllocator) Allocate(ctx context.Context) (*Browser, error) {
 	}
 	stderr.Close()
 
-	browser, err := NewBrowser(wsURL)
+	browser, err := NewBrowser(ctx, wsURL)
 	if err != nil {
 		return nil, err
 	}
 	browser.UserDataDir = dataDir
+	browser.Start(ctx)
 	return browser, nil
 }
 

browser.go

@@ -8,10 +8,13 @@ package chromedp
 
 import (
 	"context"
+	"encoding/json"
 	"log"
 	"sync/atomic"
 
 	"github.com/chromedp/cdproto"
+	"github.com/chromedp/cdproto/cdp"
+	"github.com/chromedp/cdproto/target"
 	"github.com/mailru/easyjson"
 )
 
@@ -21,25 +24,38 @@ import (
 type Browser struct {
 	UserDataDir string
 
+	pages map[target.SessionID]*Target
+
 	conn Transport
 
 	// next is the next message id.
 	next int64
 
+	cmdQueue chan cmdJob
+
+	// qres is the incoming command result queue.
+	qres chan *cdproto.Message
+
 	// logging funcs
 	logf func(string, ...interface{})
 	errf func(string, ...interface{})
 }
 
+type cmdJob struct {
+	msg  *cdproto.Message
+	resp chan *cdproto.Message
+}
+
 // NewBrowser creates a new browser.
-func NewBrowser(urlstr string, opts ...BrowserOption) (*Browser, error) {
+func NewBrowser(ctx context.Context, urlstr string, opts ...BrowserOption) (*Browser, error) {
-	conn, err := Dial(ForceIP(urlstr))
+	conn, err := DialContext(ctx, ForceIP(urlstr))
 	if err != nil {
 		return nil, err
 	}
 
 	b := &Browser{
 		conn:  conn,
+		pages: make(map[target.SessionID]*Target, 1024),
 		logf:  log.Printf,
 	}
 
@@ -72,25 +88,182 @@ func (b *Browser) Shutdown() error {
 // send writes the supplied message and params.
 func (b *Browser) send(method cdproto.MethodType, params easyjson.RawMessage) error {
 	msg := &cdproto.Message{
-		Method: method,
 		ID:     atomic.AddInt64(&b.next, 1),
+		Method: method,
 		Params: params,
 	}
-	buf, err := msg.MarshalJSON()
+	return b.conn.Write(msg)
-	if err != nil {
-		return err
-	}
-	return b.conn.Write(buf)
 }
 
-// sendToTarget writes the supplied message to the target.
+func (b *Browser) executorForTarget(ctx context.Context, sessionID target.SessionID) *Target {
-func (b *Browser) sendToTarget(targetID string, method cdproto.MethodType, params easyjson.RawMessage) error {
+	if sessionID == "" {
+		panic("empty session ID")
+	}
+	if t, ok := b.pages[sessionID]; ok {
+		return t
+	}
+	t := &Target{
+		browser:   b,
+		sessionID: sessionID,
+
+		eventQueue: make(chan *cdproto.Message, 1024),
+		waitQueue:  make(chan func(cur *cdp.Frame) bool, 1024),
+		frames:     make(map[cdp.FrameID]*cdp.Frame),
+
+		logf: b.logf,
+		errf: b.errf,
+	}
+	go t.run(ctx)
+	b.pages[sessionID] = t
+	return t
+}
+
+func (b *Browser) Execute(ctx context.Context, method string, params json.Marshaler, res json.Unmarshaler) error {
+	paramsMsg := emptyObj
+	if params != nil {
+		var err error
+		if paramsMsg, err = json.Marshal(params); err != nil {
+			return err
+		}
+	}
+
+	id := atomic.AddInt64(&b.next, 1)
+	ch := make(chan *cdproto.Message, 1)
+	b.cmdQueue <- cmdJob{
+		msg: &cdproto.Message{
+			ID:     id,
+			Method: cdproto.MethodType(method),
+			Params: paramsMsg,
+		},
+		resp: ch,
+	}
+	select {
+	case msg := <-ch:
+		switch {
+		case msg == nil:
+			return ErrChannelClosed
+		case msg.Error != nil:
+			return msg.Error
+		case res != nil:
+			return json.Unmarshal(msg.Result, res)
+		}
+	case <-ctx.Done():
+		return ctx.Err()
+	}
 	return nil
 }
 
-// CreateContext creates a new browser context.
+func (b *Browser) Start(ctx context.Context) {
-func (b *Browser) CreateContext() (context.Context, error) {
+	b.cmdQueue = make(chan cmdJob)
-	return nil, nil
+	b.qres = make(chan *cdproto.Message)
+
+	go b.run(ctx)
+}
+
+func (b *Browser) run(ctx context.Context) {
+	defer b.conn.Close()
+
+	// add cancel to context
+	ctx, cancel := context.WithCancel(ctx)
+	defer cancel()
+
+	go func() {
+		defer cancel()
+
+		for {
+			select {
+			case <-ctx.Done():
+				return
+			default:
+				// continue below
+			}
+			msg, err := b.conn.Read()
+			if err != nil {
+				return
+			}
+			var sessionID target.SessionID
+			if msg.Method == cdproto.EventTargetReceivedMessageFromTarget {
+				recv := new(target.EventReceivedMessageFromTarget)
+				if err := json.Unmarshal(msg.Params, recv); err != nil {
+					b.errf("%s", err)
+					continue
+				}
+				sessionID = recv.SessionID
+				msg = new(cdproto.Message)
+				if err := json.Unmarshal([]byte(recv.Message), msg); err != nil {
+					b.errf("%s", err)
+					continue
+				}
+			}
+
+			switch {
+			case msg.Method != "":
+				if sessionID == "" {
+					// TODO: are we interested in
+					// these events?
+					continue
+				}
+
+				page, ok := b.pages[sessionID]
+				if !ok {
+					b.errf("unknown session ID %q", sessionID)
+					continue
+				}
+				select {
+				case page.eventQueue <- msg:
+				default:
+					panic("eventQueue is full")
+				}
+
+			case msg.ID != 0:
+				b.qres <- msg
+
+			default:
+				b.errf("ignoring malformed incoming message (missing id or method): %#v", msg)
+			}
+		}
+	}()
+
+	respByID := make(map[int64]chan *cdproto.Message)
+
+	// process queues
+	for {
+		select {
+		case res := <-b.qres:
+			resp, ok := respByID[res.ID]
+			if !ok {
+				b.errf("id %d not present in response map", res.ID)
+				continue
+			}
+			if resp != nil {
+				// resp could be nil, if we're not interested in
+				// this response; for CommandSendMessageToTarget.
+				resp <- res
+				close(resp)
+			}
+			delete(respByID, res.ID)
+
+		case q := <-b.cmdQueue:
+			if _, ok := respByID[q.msg.ID]; ok {
+				b.errf("id %d already present in response map", q.msg.ID)
+				continue
+			}
+			respByID[q.msg.ID] = q.resp
+
+			if q.msg.Method == "" {
+				// Only register the chananel in respByID;
+				// useful for CommandSendMessageToTarget.
+				continue
+			}
+			if err := b.conn.Write(q.msg); err != nil {
+				b.errf("%s", err)
+				continue
+			}
+
+		case <-ctx.Done():
+			return
+		}
+	}
 }
 
 // BrowserOption is a browser option.

conn.go

@@ -1,10 +1,12 @@
 package chromedp
 
 import (
+	"context"
 	"io"
 	"net"
 	"strings"
 
+	"github.com/chromedp/cdproto"
 	"github.com/gorilla/websocket"
 )
 
@@ -18,8 +20,8 @@ var (
 
 // Transport is the common interface to send/receive messages to a target.
 type Transport interface {
-	Read() ([]byte, error)
+	Read() (*cdproto.Message, error)
-	Write([]byte) error
+	Write(*cdproto.Message) error
 	io.Closer
 }
 
@@ -29,28 +31,28 @@ type Conn struct {
 }
 
 // Read reads the next message.
-func (c *Conn) Read() ([]byte, error) {
+func (c *Conn) Read() (*cdproto.Message, error) {
-	_, buf, err := c.ReadMessage()
+	msg := new(cdproto.Message)
-	if err != nil {
+	if err := c.ReadJSON(msg); err != nil {
 		return nil, err
 	}
-	return buf, nil
+	return msg, nil
 }
 
 // Write writes a message.
-func (c *Conn) Write(buf []byte) error {
+func (c *Conn) Write(msg *cdproto.Message) error {
-	return c.WriteMessage(websocket.TextMessage, buf)
+	return c.WriteJSON(msg)
 }
 
 // Dial dials the specified websocket URL using gorilla/websocket.
-func Dial(urlstr string) (*Conn, error) {
+func DialContext(ctx context.Context, urlstr string) (*Conn, error) {
 	d := &websocket.Dialer{
 		ReadBufferSize:  DefaultReadBufferSize,
 		WriteBufferSize: DefaultWriteBufferSize,
 	}
 
 	// connect
-	conn, _, err := d.Dial(urlstr, nil)
+	conn, _, err := d.DialContext(ctx, urlstr, nil)
 	if err != nil {
 		return nil, err
 	}

context.go

@@ -3,7 +3,15 @@ package chromedp
 import (
 	"context"
 	"encoding/json"
-	"net/http"
+	"fmt"
+
+	"github.com/chromedp/cdproto/css"
+	"github.com/chromedp/cdproto/dom"
+	"github.com/chromedp/cdproto/inspector"
+	"github.com/chromedp/cdproto/log"
+	"github.com/chromedp/cdproto/page"
+	"github.com/chromedp/cdproto/runtime"
+	"github.com/chromedp/cdproto/target"
 )
 
 // Executor
@@ -16,10 +24,8 @@ type Context struct {
 	Allocator Allocator
 
 	browser *Browser
-	handler *TargetHandler
 
-	logf func(string, ...interface{})
+	sessionID target.SessionID
-	errf func(string, ...interface{})
 }
 
 // Wait can be called after cancelling the context containing Context, to block
@@ -75,41 +81,47 @@ func Run(ctx context.Context, action Action) error {
 		}
 		c.browser = browser
 	}
-	if c.handler == nil {
+	if c.sessionID == "" {
-		if err := c.newHandler(ctx); err != nil {
+		if err := c.newSession(ctx); err != nil {
 			return err
 		}
 	}
-	return action.Do(ctx, c.handler)
+	return action.Do(ctx, c.browser.executorForTarget(ctx, c.sessionID))
 }
 
-func (c *Context) newHandler(ctx context.Context) error {
+func (c *Context) newSession(ctx context.Context) error {
-	// TODO: add RemoteAddr() to the Transport interface?
+	create := target.CreateTarget("about:blank")
-	conn := c.browser.conn.(*Conn).Conn
+	targetID, err := create.Do(ctx, c.browser)
-	addr := conn.RemoteAddr()
-	url := "http://" + addr.String() + "/json/new"
-	resp, err := http.Get(url)
 	if err != nil {
 		return err
 	}
-	defer resp.Body.Close()
+
-	var wurl withWebsocketURL
+	attach := target.AttachToTarget(targetID)
-	if err := json.NewDecoder(resp.Body).Decode(&wurl); err != nil {
+	sessionID, err := attach.Do(ctx, c.browser)
-		return err
-	}
-	c.handler, err = NewTargetHandler(wurl.WebsocketURL)
 	if err != nil {
 		return err
 	}
-	if err := c.handler.Run(ctx); err != nil {
+
-		return err
+	target := c.browser.executorForTarget(ctx, sessionID)
+
+	// enable domains
+	for _, enable := range []Action{
+		log.Enable(),
+		runtime.Enable(),
+		//network.Enable(),
+		inspector.Enable(),
+		page.Enable(),
+		dom.Enable(),
+		css.Enable(),
+	} {
+		if err := enable.Do(ctx, target); err != nil {
+			return fmt.Errorf("unable to execute %T: %v", enable, err)
 		}
+	}
+
+	c.sessionID = sessionID
 	return nil
 }
 
-type withWebsocketURL struct {
-	WebsocketURL string `json:"webSocketDebuggerUrl"`
-}
-
 // ContextOption
 type ContextOption func(*Context)

handler.go

@@ -3,235 +3,138 @@ package chromedp
 import (
 	"context"
 	"encoding/json"
-	"fmt"
-	"reflect"
-	goruntime "runtime"
-	"strings"
 	"sync"
+	"sync/atomic"
 	"time"
 
 	"github.com/mailru/easyjson"
 
 	"github.com/chromedp/cdproto"
 	"github.com/chromedp/cdproto/cdp"
-	"github.com/chromedp/cdproto/css"
 	"github.com/chromedp/cdproto/dom"
 	"github.com/chromedp/cdproto/inspector"
-	"github.com/chromedp/cdproto/log"
 	"github.com/chromedp/cdproto/page"
-	"github.com/chromedp/cdproto/runtime"
+	"github.com/chromedp/cdproto/target"
 )
 
-// TargetHandler manages a Chrome DevTools Protocol target.
+// Target manages a Chrome DevTools Protocol target.
-type TargetHandler struct {
+type Target struct {
-	conn Transport
+	browser   *Browser
+	sessionID target.SessionID
+
+	waitQueue  chan func(cur *cdp.Frame) bool
+	eventQueue chan *cdproto.Message
+
+	// below are the old TargetHandler fields.
 
 	// frames is the set of encountered frames.
 	frames map[cdp.FrameID]*cdp.Frame
 
-	// cur is the current top level frame.
+	// cur is the current top level frame. TODO: delete mutex
+	curMu sync.RWMutex
 	cur   *cdp.Frame
 
-	// qcmd is the outgoing message queue.
-	qcmd chan *cdproto.Message
-
-	// qres is the incoming command result queue.
-	qres chan *cdproto.Message
-
-	// qevents is the incoming event queue.
-	qevents chan *cdproto.Message
-
-	// detached is closed when the detached event is received.
-	detached chan *inspector.EventDetached
-
-	pageWaitGroup, domWaitGroup *sync.WaitGroup
-
-	// last is the last sent message identifier.
-	last  int64
-	lastm sync.Mutex
-
-	// res is the id->result channel map.
-	res   map[int64]chan *cdproto.Message
-	resrw sync.RWMutex
-
 	// logging funcs
-	logf, debugf, errf func(string, ...interface{})
+	logf, errf func(string, ...interface{})
-
-	sync.RWMutex
 }
 
-// NewTargetHandler creates a new handler for the specified client target.
+func (t *Target) run(ctx context.Context) {
-func NewTargetHandler(urlstr string, opts ...TargetHandlerOption) (*TargetHandler, error) {
+	for {
-	conn, err := Dial(urlstr)
+		select {
+		case <-ctx.Done():
+			return
+		case msg := <-t.eventQueue:
+			//fmt.Printf("%d %s: %s\n", msg.ID, msg.Method, msg.Params)
+			if err := t.processEvent(ctx, msg); err != nil {
+				t.errf("could not process event: %v", err)
+				continue
+			}
+		default:
+			// prevent busy spinning. TODO: do better
+			time.Sleep(5 * time.Millisecond)
+			n := len(t.waitQueue)
+			if n == 0 {
+				continue
+			}
+
+			t.curMu.RLock()
+			cur := t.cur
+			t.curMu.RUnlock()
+			if cur == nil {
+				continue
+			}
+
+			for i := 0; i < n; i++ {
+				fn := <-t.waitQueue
+				if !fn(cur) {
+					// try again later.
+					t.waitQueue <- fn
+				}
+			}
+		}
+	}
+}
+
+func (t *Target) Execute(ctx context.Context, method string, params json.Marshaler, res json.Unmarshaler) error {
+	paramsMsg := emptyObj
+	if params != nil {
+		var err error
+		if paramsMsg, err = json.Marshal(params); err != nil {
+			return err
+		}
+	}
+	innerID := atomic.AddInt64(&t.browser.next, 1)
+	msg := &cdproto.Message{
+		ID:     innerID,
+		Method: cdproto.MethodType(method),
+		Params: paramsMsg,
+	}
+	msgJSON, err := json.Marshal(msg)
 	if err != nil {
-		return nil, err
+		return err
+	}
+	sendParams := target.SendMessageToTarget(string(msgJSON)).
+		WithSessionID(t.sessionID)
+	sendParamsJSON, _ := json.Marshal(sendParams)
+
+	// We want to grab the response from the inner message.
+	ch := make(chan *cdproto.Message, 1)
+	t.browser.cmdQueue <- cmdJob{
+		msg:  &cdproto.Message{ID: innerID},
+		resp: ch,
 	}
 
-	h := &TargetHandler{
+	// The response from the outer message is uninteresting; pass a nil
-		conn: conn,
+	// resp channel.
-		errf: func(string, ...interface{}) {},
+	outerID := atomic.AddInt64(&t.browser.next, 1)
+	t.browser.cmdQueue <- cmdJob{
+		msg: &cdproto.Message{
+			ID:     outerID,
+			Method: target.CommandSendMessageToTarget,
+			Params: sendParamsJSON,
+		},
 	}
 
-	for _, o := range opts {
+	select {
-		o(h)
+	case msg := <-ch:
+		switch {
+		case msg == nil:
+			return ErrChannelClosed
+		case msg.Error != nil:
+			return msg.Error
+		case res != nil:
+			return json.Unmarshal(msg.Result, res)
 		}
-
+	case <-ctx.Done():
-	return h, nil
+		return ctx.Err()
 	}
-
-// Run starts the processing of commands and events of the client target
-// provided to NewTargetHandler.
-//
-// Callers can stop Run by closing the passed context.
-func (h *TargetHandler) Run(ctxt context.Context) error {
-	// reset
-	h.Lock()
-	h.frames = make(map[cdp.FrameID]*cdp.Frame)
-	h.qcmd = make(chan *cdproto.Message)
-	h.qres = make(chan *cdproto.Message)
-	h.qevents = make(chan *cdproto.Message)
-	h.res = make(map[int64]chan *cdproto.Message)
-	h.detached = make(chan *inspector.EventDetached, 1)
-	h.pageWaitGroup = new(sync.WaitGroup)
-	h.domWaitGroup = new(sync.WaitGroup)
-	h.Unlock()
-
-	// run
-	go h.run(ctxt)
-
-	// enable domains
-	for _, a := range []Action{
-		log.Enable(),
-		runtime.Enable(),
-		//network.Enable(),
-		inspector.Enable(),
-		page.Enable(),
-		dom.Enable(),
-		css.Enable(),
-	} {
-		if err := a.Do(ctxt, h); err != nil {
-			return fmt.Errorf("unable to execute %s: %v", reflect.TypeOf(a), err)
-		}
-	}
-
-	h.Lock()
-
-	// get page resources
-	tree, err := page.GetResourceTree().Do(ctxt, h)
-	if err != nil {
-		return fmt.Errorf("unable to get resource tree: %v", err)
-	}
-
-	h.frames[tree.Frame.ID] = tree.Frame
-	h.cur = tree.Frame
-
-	for _, c := range tree.ChildFrames {
-		h.frames[c.Frame.ID] = c.Frame
-	}
-
-	h.Unlock()
-
-	h.documentUpdated(ctxt)
-
 	return nil
 }
 
-// run handles the actual message processing to / from the web socket connection.
+// below are the old TargetHandler methods.
-func (h *TargetHandler) run(ctxt context.Context) {
-	defer h.conn.Close()
-
-	// add cancel to context
-	ctxt, cancel := context.WithCancel(ctxt)
-	defer cancel()
-
-	go func() {
-		defer cancel()
-
-		for {
-			select {
-			default:
-				msg, err := h.read()
-				if err != nil {
-					return
-				}
-
-				switch {
-				case msg.Method != "":
-					select {
-					case h.qevents <- msg:
-					case <-ctxt.Done():
-						return
-					}
-
-				case msg.ID != 0:
-					select {
-					case h.qres <- msg:
-					case <-ctxt.Done():
-						return
-					}
-
-				default:
-					h.errf("ignoring malformed incoming message (missing id or method): %#v", msg)
-				}
-
-			case <-h.detached:
-				// FIXME: should log when detached, and reason
-				return
-
-			case <-ctxt.Done():
-				return
-			}
-		}
-	}()
-
-	// process queues
-	for {
-		select {
-		case ev := <-h.qevents:
-			err := h.processEvent(ctxt, ev)
-			if err != nil {
-				h.errf("could not process event %s: %v", ev.Method, err)
-			}
-
-		case res := <-h.qres:
-			err := h.processResult(res)
-			if err != nil {
-				h.errf("could not process result for message %d: %v", res.ID, err)
-			}
-
-		case cmd := <-h.qcmd:
-			err := h.processCommand(cmd)
-			if err != nil {
-				h.errf("could not process command message %d: %v", cmd.ID, err)
-			}
-
-		case <-ctxt.Done():
-			return
-		}
-	}
-}
-
-// read reads a message from the client connection.
-func (h *TargetHandler) read() (*cdproto.Message, error) {
-	// read
-	buf, err := h.conn.Read()
-	if err != nil {
-		return nil, err
-	}
-
-	//h.debugf("-> %s", string(buf))
-
-	// unmarshal
-	msg := new(cdproto.Message)
-	if err := json.Unmarshal(buf, msg); err != nil {
-		return nil, err
-	}
-
-	return msg, nil
-}
 
 // processEvent processes an incoming event.
-func (h *TargetHandler) processEvent(ctxt context.Context, msg *cdproto.Message) error {
+func (t *Target) processEvent(ctxt context.Context, msg *cdproto.Message) error {
 	if msg == nil {
 		return ErrChannelClosed
 	}
@@ -251,46 +154,29 @@ func (h *TargetHandler) processEvent(ctxt context.Context, msg *cdproto.Message)
 		return err
 	}
 
-	switch e := ev.(type) {
+	switch ev.(type) {
 	case *inspector.EventDetached:
-		h.Lock()
-		defer h.Unlock()
-		h.detached <- e
 		return nil
-
 	case *dom.EventDocumentUpdated:
-		h.domWaitGroup.Wait()
+		t.documentUpdated(ctxt)
-		go h.documentUpdated(ctxt)
 		return nil
 	}
 
-	d := msg.Method.Domain()
+	switch msg.Method.Domain() {
-	if d != "Page" && d != "DOM" {
-		return nil
-	}
-
-	switch d {
 	case "Page":
-		h.pageWaitGroup.Add(1)
+		t.pageEvent(ctxt, ev)
-		go h.pageEvent(ctxt, ev)
-
 	case "DOM":
-		h.domWaitGroup.Add(1)
+		t.domEvent(ctxt, ev)
-		go h.domEvent(ctxt, ev)
 	}
-
 	return nil
 }
 
 // documentUpdated handles the document updated event, retrieving the document
 // root for the root frame.
-func (h *TargetHandler) documentUpdated(ctxt context.Context) {
+func (t *Target) documentUpdated(ctxt context.Context) {
-	f, err := h.WaitFrame(ctxt, cdp.EmptyFrameID)
+	t.curMu.RLock()
-	if err != nil {
+	f := t.cur
-		h.errf("could not get current frame: %v", err)
+	t.curMu.RUnlock()
-		return
-	}
-
 	f.Lock()
 	defer f.Unlock()
 
@@ -300,242 +186,33 @@ func (h *TargetHandler) documentUpdated(ctxt context.Context) {
 	}
 
 	f.Nodes = make(map[cdp.NodeID]*cdp.Node)
-	f.Root, err = dom.GetDocument().WithPierce(true).Do(ctxt, h)
+	var err error
+	f.Root, err = dom.GetDocument().WithPierce(true).Do(ctxt, t)
+	if err == context.Canceled {
+		return // TODO: perhaps not necessary, but useful to keep the tests less noisy
+	}
 	if err != nil {
-		h.errf("could not retrieve document root for %s: %v", f.ID, err)
+		t.errf("could not retrieve document root for %s: %v", f.ID, err)
 		return
 	}
 	f.Root.Invalidated = make(chan struct{})
 	walk(f.Nodes, f.Root)
 }
 
-// processResult processes an incoming command result.
-func (h *TargetHandler) processResult(msg *cdproto.Message) error {
-	h.resrw.RLock()
-	defer h.resrw.RUnlock()
-
-	ch, ok := h.res[msg.ID]
-	if !ok {
-		return fmt.Errorf("id %d not present in res map", msg.ID)
-	}
-	defer close(ch)
-
-	ch <- msg
-
-	return nil
-}
-
-// processCommand writes a command to the client connection.
-func (h *TargetHandler) processCommand(cmd *cdproto.Message) error {
-	// marshal
-	buf, err := json.Marshal(cmd)
-	if err != nil {
-		return err
-	}
-
-	//h.debugf("<- %s", string(buf))
-
-	return h.conn.Write(buf)
-}
-
 // emptyObj is an empty JSON object message.
 var emptyObj = easyjson.RawMessage([]byte(`{}`))
 
-// Execute executes commandType against the endpoint passed to Run, using the
-// provided context and params, decoding the result of the command to res.
-func (h *TargetHandler) Execute(ctxt context.Context, methodType string, params json.Marshaler, res json.Unmarshaler) error {
-	var paramsBuf easyjson.RawMessage
-	if params == nil {
-		paramsBuf = emptyObj
-	} else {
-		var err error
-		paramsBuf, err = json.Marshal(params)
-		if err != nil {
-			return err
-		}
-	}
-
-	id := h.next()
-
-	// save channel
-	ch := make(chan *cdproto.Message, 1)
-	h.resrw.Lock()
-	h.res[id] = ch
-	h.resrw.Unlock()
-
-	// queue message
-	select {
-	case h.qcmd <- &cdproto.Message{
-		ID:     id,
-		Method: cdproto.MethodType(methodType),
-		Params: paramsBuf,
-	}:
-	case <- ctxt.Done():
-		return ctxt.Err()
-	}
-
-	errch := make(chan error, 1)
-	go func() {
-		defer close(errch)
-
-		select {
-		case msg := <-ch:
-			switch {
-			case msg == nil:
-				errch <- ErrChannelClosed
-
-			case msg.Error != nil:
-				errch <- msg.Error
-
-			case res != nil:
-				errch <- json.Unmarshal(msg.Result, res)
-			}
-
-		case <-ctxt.Done():
-			errch <- ctxt.Err()
-		}
-
-		h.resrw.Lock()
-		defer h.resrw.Unlock()
-
-		delete(h.res, id)
-	}()
-
-	return <-errch
-}
-
-// next returns the next message id.
-func (h *TargetHandler) next() int64 {
-	h.lastm.Lock()
-	defer h.lastm.Unlock()
-	h.last++
-	return h.last
-}
-
-// GetRoot returns the current top level frame's root document node.
-func (h *TargetHandler) GetRoot(ctxt context.Context) (*cdp.Node, error) {
-	var root *cdp.Node
-
-	for {
-		var cur *cdp.Frame
-		select {
-		default:
-			h.RLock()
-			cur = h.cur
-			if cur != nil {
-				cur.RLock()
-				root = cur.Root
-				cur.RUnlock()
-			}
-			h.RUnlock()
-
-			if cur != nil && root != nil {
-				return root, nil
-			}
-
-			time.Sleep(DefaultCheckDuration)
-
-		case <-ctxt.Done():
-			return nil, ctxt.Err()
-		}
-	}
-}
-
-// SetActive sets the currently active frame after a successful navigation.
-func (h *TargetHandler) SetActive(ctxt context.Context, id cdp.FrameID) error {
-	// get frame
-	f, err := h.WaitFrame(ctxt, id)
-	if err != nil {
-		return err
-	}
-
-	h.Lock()
-	defer h.Unlock()
-
-	h.cur = f
-
-	return nil
-}
-
-// WaitFrame waits for a frame to be loaded using the provided context.
-func (h *TargetHandler) WaitFrame(ctxt context.Context, id cdp.FrameID) (*cdp.Frame, error) {
-	// TODO: fix this
-	timeout := time.After(time.Second)
-
-	for {
-		select {
-		default:
-			var f *cdp.Frame
-			var ok bool
-
-			h.RLock()
-			if id == cdp.EmptyFrameID {
-				f, ok = h.cur, h.cur != nil
-			} else {
-				f, ok = h.frames[id]
-			}
-			h.RUnlock()
-
-			if ok {
-				return f, nil
-			}
-
-			time.Sleep(DefaultCheckDuration)
-
-		case <-ctxt.Done():
-			return nil, ctxt.Err()
-
-		case <-timeout:
-			return nil, fmt.Errorf("timeout waiting for frame `%s`", id)
-		}
-	}
-}
-
-// WaitNode waits for a node to be loaded using the provided context.
-func (h *TargetHandler) WaitNode(ctxt context.Context, f *cdp.Frame, id cdp.NodeID) (*cdp.Node, error) {
-	// TODO: fix this
-	timeout := time.After(time.Second)
-
-	for {
-		select {
-		default:
-			var n *cdp.Node
-			var ok bool
-
-			f.RLock()
-			n, ok = f.Nodes[id]
-			f.RUnlock()
-
-			if n != nil && ok {
-				return n, nil
-			}
-
-			time.Sleep(DefaultCheckDuration)
-
-		case <-ctxt.Done():
-			return nil, ctxt.Err()
-
-		case <-timeout:
-			return nil, fmt.Errorf("timeout waiting for node `%d`", id)
-		}
-	}
-}
-
 // pageEvent handles incoming page events.
-func (h *TargetHandler) pageEvent(ctxt context.Context, ev interface{}) {
+func (t *Target) pageEvent(ctxt context.Context, ev interface{}) {
-	defer h.pageWaitGroup.Done()
-
 	var id cdp.FrameID
 	var op frameOp
 
 	switch e := ev.(type) {
 	case *page.EventFrameNavigated:
-		h.Lock()
+		t.frames[e.Frame.ID] = e.Frame
-		h.frames[e.Frame.ID] = e.Frame
+		t.curMu.Lock()
-		if h.cur != nil && h.cur.ID == e.Frame.ID {
+		t.cur = e.Frame
-			h.cur = e.Frame
+		t.curMu.Unlock()
-		}
-		h.Unlock()
 		return
 
 	case *page.EventFrameAttached:
@@ -545,7 +222,10 @@ func (h *TargetHandler) pageEvent(ctxt context.Context, ev interface{}) {
 		id, op = e.FrameID, frameDetached
 
 	case *page.EventFrameStartedLoading:
-		id, op = e.FrameID, frameStartedLoading
+		// TODO: this happens before EventFrameNavigated, so the frame
+		// isn't in t.frames yet.
+		//id, op = e.FrameID, frameStartedLoading
+		return
 
 	case *page.EventFrameStoppedLoading:
 		id, op = e.FrameID, frameStoppedLoading
@@ -563,18 +243,11 @@ func (h *TargetHandler) pageEvent(ctxt context.Context, ev interface{}) {
 		return
 
 	default:
-		h.errf("unhandled page event %s", reflect.TypeOf(ev))
+		t.errf("unhandled page event %T", ev)
 		return
 	}
 
-	f, err := h.WaitFrame(ctxt, id)
+	f := t.frames[id]
-	if err != nil {
-		h.errf("could not get frame %s: %v", id, err)
-		return
-	}
-
-	h.Lock()
-	defer h.Unlock()
 
 	f.Lock()
 	defer f.Unlock()
@@ -583,15 +256,10 @@ func (h *TargetHandler) pageEvent(ctxt context.Context, ev interface{}) {
 }
 
 // domEvent handles incoming DOM events.
-func (h *TargetHandler) domEvent(ctxt context.Context, ev interface{}) {
+func (t *Target) domEvent(ctxt context.Context, ev interface{}) {
-	defer h.domWaitGroup.Done()
+	t.curMu.RLock()
-
+	f := t.cur
-	// wait current frame
+	t.curMu.RUnlock()
-	f, err := h.WaitFrame(ctxt, cdp.EmptyFrameID)
-	if err != nil {
-		h.errf("could not process DOM event %s: %v", reflect.TypeOf(ev), err)
-		return
-	}
 
 	var id cdp.NodeID
 	var op nodeOp
@@ -620,12 +288,6 @@ func (h *TargetHandler) domEvent(ctxt context.Context, ev interface{}) {
 		id, op = e.NodeID, childNodeCountUpdated(e.ChildNodeCount)
 
 	case *dom.EventChildNodeInserted:
-		if e.PreviousNodeID != cdp.EmptyNodeID {
-			_, err = h.WaitNode(ctxt, f, e.PreviousNodeID)
-			if err != nil {
-				return
-			}
-		}
 		id, op = e.ParentNodeID, childNodeInserted(f.Nodes, e.PreviousNodeID, e.Node)
 
 	case *dom.EventChildNodeRemoved:
@@ -647,29 +309,20 @@ func (h *TargetHandler) domEvent(ctxt context.Context, ev interface{}) {
 		id, op = e.InsertionPointID, distributedNodesUpdated(e.DistributedNodes)
 
 	default:
-		h.errf("unhandled node event %s", reflect.TypeOf(ev))
+		t.errf("unhandled node event %T", ev)
 		return
 	}
 
-	// retrieve node
+	n, ok := f.Nodes[id]
-	n, err := h.WaitNode(ctxt, f, id)
+	if !ok {
-	if err != nil {
+		// Node ID has been invalidated. Nothing to do.
-		s := strings.TrimSuffix(goruntime.FuncForPC(reflect.ValueOf(op).Pointer()).Name(), ".func1")
-		i := strings.LastIndex(s, ".")
-		if i != -1 {
-			s = s[i+1:]
-		}
-		h.errf("could not perform (%s) operation on node %d (wait node): %v", s, id, err)
 		return
 	}
 
-	h.Lock()
-	defer h.Unlock()
-
 	f.Lock()
 	defer f.Unlock()
 
 	op(n)
 }
 
-type TargetHandlerOption func(*TargetHandler)
+type TargetOption func(*Target)

nav.go

@@ -11,17 +11,8 @@ import (
 // Navigate navigates the current frame.
 func Navigate(urlstr string) Action {
 	return ActionFunc(func(ctxt context.Context, h cdp.Executor) error {
-		th, ok := h.(*TargetHandler)
+		_, _, _, err := page.Navigate(urlstr).Do(ctxt, h)
-		if !ok {
-			return ErrInvalidHandler
-		}
-
-		frameID, _, _, err := page.Navigate(urlstr).Do(ctxt, th)
-		if err != nil {
 		return err
-		}
-
-		return th.SetActive(ctxt, frameID)
 	})
 }
 

query.go

@@ -25,7 +25,7 @@ func Nodes(sel interface{}, nodes *[]*cdp.Node, opts ...QueryOption) Action {
 		panic("nodes cannot be nil")
 	}
 
-	return QueryAfter(sel, func(ctxt context.Context, h *TargetHandler, n ...*cdp.Node) error {
+	return QueryAfter(sel, func(ctxt context.Context, h *Target, n ...*cdp.Node) error {
 		*nodes = n
 		return nil
 	}, opts...)
@@ -37,7 +37,7 @@ func NodeIDs(sel interface{}, ids *[]cdp.NodeID, opts ...QueryOption) Action {
 		panic("nodes cannot be nil")
 	}
 
-	return QueryAfter(sel, func(ctxt context.Context, h *TargetHandler, nodes ...*cdp.Node) error {
+	return QueryAfter(sel, func(ctxt context.Context, h *Target, nodes ...*cdp.Node) error {
 		nodeIDs := make([]cdp.NodeID, len(nodes))
 		for i, n := range nodes {
 			nodeIDs[i] = n.NodeID
@@ -51,7 +51,7 @@ func NodeIDs(sel interface{}, ids *[]cdp.NodeID, opts ...QueryOption) Action {
 
 // Focus focuses the first node matching the selector.
 func Focus(sel interface{}, opts ...QueryOption) Action {
-	return QueryAfter(sel, func(ctxt context.Context, h *TargetHandler, nodes ...*cdp.Node) error {
+	return QueryAfter(sel, func(ctxt context.Context, h *Target, nodes ...*cdp.Node) error {
 		if len(nodes) < 1 {
 			return fmt.Errorf("selector `%s` did not return any nodes", sel)
 		}
@@ -62,7 +62,7 @@ func Focus(sel interface{}, opts ...QueryOption) Action {
 
 // Blur unfocuses (blurs) the first node matching the selector.
 func Blur(sel interface{}, opts ...QueryOption) Action {
-	return QueryAfter(sel, func(ctxt context.Context, h *TargetHandler, nodes ...*cdp.Node) error {
+	return QueryAfter(sel, func(ctxt context.Context, h *Target, nodes ...*cdp.Node) error {
 		if len(nodes) < 1 {
 			return fmt.Errorf("selector `%s` did not return any nodes", sel)
 		}
@@ -87,7 +87,7 @@ func Dimensions(sel interface{}, model **dom.BoxModel, opts ...QueryOption) Acti
 	if model == nil {
 		panic("model cannot be nil")
 	}
-	return QueryAfter(sel, func(ctxt context.Context, h *TargetHandler, nodes ...*cdp.Node) error {
+	return QueryAfter(sel, func(ctxt context.Context, h *Target, nodes ...*cdp.Node) error {
 		if len(nodes) < 1 {
 			return fmt.Errorf("selector `%s` did not return any nodes", sel)
 		}
@@ -103,7 +103,7 @@ func Text(sel interface{}, text *string, opts ...QueryOption) Action {
 		panic("text cannot be nil")
 	}
 
-	return QueryAfter(sel, func(ctxt context.Context, h *TargetHandler, nodes ...*cdp.Node) error {
+	return QueryAfter(sel, func(ctxt context.Context, h *Target, nodes ...*cdp.Node) error {
 		if len(nodes) < 1 {
 			return fmt.Errorf("selector `%s` did not return any nodes", sel)
 		}
@@ -114,7 +114,7 @@ func Text(sel interface{}, text *string, opts ...QueryOption) Action {
 
 // Clear clears the values of any input/textarea nodes matching the selector.
 func Clear(sel interface{}, opts ...QueryOption) Action {
-	return QueryAfter(sel, func(ctxt context.Context, h *TargetHandler, nodes ...*cdp.Node) error {
+	return QueryAfter(sel, func(ctxt context.Context, h *Target, nodes ...*cdp.Node) error {
 		if len(nodes) < 1 {
 			return fmt.Errorf("selector `%s` did not return any nodes", sel)
 		}
@@ -190,7 +190,7 @@ func Attributes(sel interface{}, attributes *map[string]string, opts ...QueryOpt
 		panic("attributes cannot be nil")
 	}
 
-	return QueryAfter(sel, func(ctxt context.Context, h *TargetHandler, nodes ...*cdp.Node) error {
+	return QueryAfter(sel, func(ctxt context.Context, h *Target, nodes ...*cdp.Node) error {
 		if len(nodes) < 1 {
 			return fmt.Errorf("selector `%s` did not return any nodes", sel)
 		}
@@ -219,7 +219,7 @@ func AttributesAll(sel interface{}, attributes *[]map[string]string, opts ...Que
 		panic("attributes cannot be nil")
 	}
 
-	return QueryAfter(sel, func(ctxt context.Context, h *TargetHandler, nodes ...*cdp.Node) error {
+	return QueryAfter(sel, func(ctxt context.Context, h *Target, nodes ...*cdp.Node) error {
 		if len(nodes) < 1 {
 			return fmt.Errorf("selector `%s` did not return any nodes", sel)
 		}
@@ -243,7 +243,7 @@ func AttributesAll(sel interface{}, attributes *[]map[string]string, opts ...Que
 // SetAttributes sets the element attributes for the first node matching the
 // selector.
 func SetAttributes(sel interface{}, attributes map[string]string, opts ...QueryOption) Action {
-	return QueryAfter(sel, func(ctxt context.Context, h *TargetHandler, nodes ...*cdp.Node) error {
+	return QueryAfter(sel, func(ctxt context.Context, h *Target, nodes ...*cdp.Node) error {
 		if len(nodes) < 1 {
 			return errors.New("expected at least one element")
 		}
@@ -265,7 +265,7 @@ func AttributeValue(sel interface{}, name string, value *string, ok *bool, opts
 		panic("value cannot be nil")
 	}
 
-	return QueryAfter(sel, func(ctxt context.Context, h *TargetHandler, nodes ...*cdp.Node) error {
+	return QueryAfter(sel, func(ctxt context.Context, h *Target, nodes ...*cdp.Node) error {
 		if len(nodes) < 1 {
 			return errors.New("expected at least one element")
 		}
@@ -295,7 +295,7 @@ func AttributeValue(sel interface{}, name string, value *string, ok *bool, opts
 // SetAttributeValue sets the element attribute with name to value for the
 // first node matching the selector.
 func SetAttributeValue(sel interface{}, name, value string, opts ...QueryOption) Action {
-	return QueryAfter(sel, func(ctxt context.Context, h *TargetHandler, nodes ...*cdp.Node) error {
+	return QueryAfter(sel, func(ctxt context.Context, h *Target, nodes ...*cdp.Node) error {
 		if len(nodes) < 1 {
 			return fmt.Errorf("selector `%s` did not return any nodes", sel)
 		}
@@ -307,7 +307,7 @@ func SetAttributeValue(sel interface{}, name, value string, opts ...QueryOption)
 // RemoveAttribute removes the element attribute with name from the first node
 // matching the selector.
 func RemoveAttribute(sel interface{}, name string, opts ...QueryOption) Action {
-	return QueryAfter(sel, func(ctxt context.Context, h *TargetHandler, nodes ...*cdp.Node) error {
+	return QueryAfter(sel, func(ctxt context.Context, h *Target, nodes ...*cdp.Node) error {
 		if len(nodes) < 1 {
 			return fmt.Errorf("selector `%s` did not return any nodes", sel)
 		}
@@ -322,7 +322,7 @@ func JavascriptAttribute(sel interface{}, name string, res interface{}, opts ...
 	if res == nil {
 		panic("res cannot be nil")
 	}
-	return QueryAfter(sel, func(ctxt context.Context, h *TargetHandler, nodes ...*cdp.Node) error {
+	return QueryAfter(sel, func(ctxt context.Context, h *Target, nodes ...*cdp.Node) error {
 		if len(nodes) < 1 {
 			return fmt.Errorf("selector `%s` did not return any nodes", sel)
 		}
@@ -334,7 +334,7 @@ func JavascriptAttribute(sel interface{}, name string, res interface{}, opts ...
 // SetJavascriptAttribute sets the javascript attribute for the first node
 // matching the selector.
 func SetJavascriptAttribute(sel interface{}, name, value string, opts ...QueryOption) Action {
-	return QueryAfter(sel, func(ctxt context.Context, h *TargetHandler, nodes ...*cdp.Node) error {
+	return QueryAfter(sel, func(ctxt context.Context, h *Target, nodes ...*cdp.Node) error {
 		if len(nodes) < 1 {
 			return fmt.Errorf("selector `%s` did not return any nodes", sel)
 		}
@@ -370,7 +370,7 @@ func InnerHTML(sel interface{}, html *string, opts ...QueryOption) Action {
 
 // Click sends a mouse click event to the first node matching the selector.
 func Click(sel interface{}, opts ...QueryOption) Action {
-	return QueryAfter(sel, func(ctxt context.Context, h *TargetHandler, nodes ...*cdp.Node) error {
+	return QueryAfter(sel, func(ctxt context.Context, h *Target, nodes ...*cdp.Node) error {
 		if len(nodes) < 1 {
 			return fmt.Errorf("selector `%s` did not return any nodes", sel)
 		}
@@ -382,7 +382,7 @@ func Click(sel interface{}, opts ...QueryOption) Action {
 // DoubleClick sends a mouse double click event to the first node matching the
 // selector.
 func DoubleClick(sel interface{}, opts ...QueryOption) Action {
-	return QueryAfter(sel, func(ctxt context.Context, h *TargetHandler, nodes ...*cdp.Node) error {
+	return QueryAfter(sel, func(ctxt context.Context, h *Target, nodes ...*cdp.Node) error {
 		if len(nodes) < 1 {
 			return fmt.Errorf("selector `%s` did not return any nodes", sel)
 		}
@@ -397,7 +397,7 @@ func DoubleClick(sel interface{}, opts ...QueryOption) Action {
 // Note: when selector matches a input[type="file"] node, then dom.SetFileInputFiles
 // is used to set the upload path of the input node to v.
 func SendKeys(sel interface{}, v string, opts ...QueryOption) Action {
-	return QueryAfter(sel, func(ctxt context.Context, h *TargetHandler, nodes ...*cdp.Node) error {
+	return QueryAfter(sel, func(ctxt context.Context, h *Target, nodes ...*cdp.Node) error {
 		if len(nodes) < 1 {
 			return fmt.Errorf("selector `%s` did not return any nodes", sel)
 		}
@@ -426,7 +426,7 @@ func SendKeys(sel interface{}, v string, opts ...QueryOption) Action {
 // SetUploadFiles sets the files to upload (ie, for a input[type="file"] node)
 // for the first node matching the selector.
 func SetUploadFiles(sel interface{}, files []string, opts ...QueryOption) Action {
-	return QueryAfter(sel, func(ctxt context.Context, h *TargetHandler, nodes ...*cdp.Node) error {
+	return QueryAfter(sel, func(ctxt context.Context, h *Target, nodes ...*cdp.Node) error {
 		if len(nodes) < 1 {
 			return fmt.Errorf("selector `%s` did not return any nodes", sel)
 		}
@@ -441,7 +441,7 @@ func Screenshot(sel interface{}, picbuf *[]byte, opts ...QueryOption) Action {
 		panic("picbuf cannot be nil")
 	}
 
-	return QueryAfter(sel, func(ctxt context.Context, h *TargetHandler, nodes ...*cdp.Node) error {
+	return QueryAfter(sel, func(ctxt context.Context, h *Target, nodes ...*cdp.Node) error {
 		if len(nodes) < 1 {
 			return fmt.Errorf("selector `%s` did not return any nodes", sel)
 		}
@@ -497,7 +497,7 @@ func Screenshot(sel interface{}, picbuf *[]byte, opts ...QueryOption) Action {
 // Submit is an action that submits the form of the first node matching the
 // selector belongs to.
 func Submit(sel interface{}, opts ...QueryOption) Action {
-	return QueryAfter(sel, func(ctxt context.Context, h *TargetHandler, nodes ...*cdp.Node) error {
+	return QueryAfter(sel, func(ctxt context.Context, h *Target, nodes ...*cdp.Node) error {
 		if len(nodes) < 1 {
 			return fmt.Errorf("selector `%s` did not return any nodes", sel)
 		}
@@ -519,7 +519,7 @@ func Submit(sel interface{}, opts ...QueryOption) Action {
 // Reset is an action that resets the form of the first node matching the
 // selector belongs to.
 func Reset(sel interface{}, opts ...QueryOption) Action {
-	return QueryAfter(sel, func(ctxt context.Context, h *TargetHandler, nodes ...*cdp.Node) error {
+	return QueryAfter(sel, func(ctxt context.Context, h *Target, nodes ...*cdp.Node) error {
 		if len(nodes) < 1 {
 			return fmt.Errorf("selector `%s` did not return any nodes", sel)
 		}
@@ -544,7 +544,7 @@ func ComputedStyle(sel interface{}, style *[]*css.ComputedProperty, opts ...Quer
 		panic("style cannot be nil")
 	}
 
-	return QueryAfter(sel, func(ctxt context.Context, h *TargetHandler, nodes ...*cdp.Node) error {
+	return QueryAfter(sel, func(ctxt context.Context, h *Target, nodes ...*cdp.Node) error {
 		if len(nodes) < 1 {
 			return fmt.Errorf("selector `%s` did not return any nodes", sel)
 		}
@@ -567,7 +567,7 @@ func MatchedStyle(sel interface{}, style **css.GetMatchedStylesForNodeReturns, o
 		panic("style cannot be nil")
 	}
 
-	return QueryAfter(sel, func(ctxt context.Context, h *TargetHandler, nodes ...*cdp.Node) error {
+	return QueryAfter(sel, func(ctxt context.Context, h *Target, nodes ...*cdp.Node) error {
 		if len(nodes) < 1 {
 			return fmt.Errorf("selector `%s` did not return any nodes", sel)
 		}
@@ -589,7 +589,7 @@ func MatchedStyle(sel interface{}, style **css.GetMatchedStylesForNodeReturns, o
 
 // ScrollIntoView scrolls the window to the first node matching the selector.
 func ScrollIntoView(sel interface{}, opts ...QueryOption) Action {
-	return QueryAfter(sel, func(ctxt context.Context, h *TargetHandler, nodes ...*cdp.Node) error {
+	return QueryAfter(sel, func(ctxt context.Context, h *Target, nodes ...*cdp.Node) error {
 		if len(nodes) < 1 {
 			return fmt.Errorf("selector `%s` did not return any nodes", sel)
 		}

query_test.go

@@ -925,6 +925,7 @@ func TestFileUpload(t *testing.T) {
 		t.Fatal(err)
 	}
 	defer os.Remove(tmpfile.Name())
+	defer tmpfile.Close()
 	if _, err := tmpfile.WriteString(uploadHTML); err != nil {
 		t.Fatal(err)
 	}

sel.go

@@ -5,7 +5,6 @@ import (
 	"fmt"
 	"strings"
 	"sync"
-	"time"
 
 	"github.com/chromedp/cdproto/cdp"
 	"github.com/chromedp/cdproto/dom"
@@ -26,9 +25,9 @@ tagname
 type Selector struct {
 	sel   interface{}
 	exp   int
-	by    func(context.Context, *TargetHandler, *cdp.Node) ([]cdp.NodeID, error)
+	by    func(context.Context, *Target, *cdp.Node) ([]cdp.NodeID, error)
-	wait  func(context.Context, *TargetHandler, *cdp.Node, ...cdp.NodeID) ([]*cdp.Node, error)
+	wait  func(context.Context, *Target, *cdp.Frame, ...cdp.NodeID) ([]*cdp.Node, error)
-	after func(context.Context, *TargetHandler, ...*cdp.Node) error
+	after func(context.Context, *Target, ...*cdp.Node) error
 }
 
 // Query is an action to query for document nodes match the specified sel and
@@ -57,15 +56,11 @@ func Query(sel interface{}, opts ...QueryOption) Action {
 
 // Do satisfies the Action interface.
 func (s *Selector) Do(ctxt context.Context, h cdp.Executor) error {
-	th, ok := h.(*TargetHandler)
+	th, ok := h.(*Target)
 	if !ok {
 		return ErrInvalidHandler
 	}
 
-	// TODO: fix this
-	ctxt, cancel := context.WithTimeout(ctxt, 100*time.Second)
-	defer cancel()
-
 	var err error
 	select {
 	case err = <-s.run(ctxt, th):
@@ -79,53 +74,35 @@ func (s *Selector) Do(ctxt context.Context, h cdp.Executor) error {
 // run runs the selector action, starting over if the original returned nodes
 // are invalidated prior to finishing the selector's by, wait, check, and after
 // funcs.
-func (s *Selector) run(ctxt context.Context, h *TargetHandler) chan error {
+func (s *Selector) run(ctxt context.Context, h *Target) chan error {
 	ch := make(chan error, 1)
+	h.waitQueue <- func(cur *cdp.Frame) bool {
+		cur.RLock()
+		root := cur.Root
+		cur.RUnlock()
 
-	go func() {
+		if root == nil {
-		defer close(ch)
+			// not ready?
-
+			return false
-		for {
-			root, err := h.GetRoot(ctxt)
-			if err != nil {
-				select {
-				case <-ctxt.Done():
-					ch <- ctxt.Err()
-					return
-				default:
-					continue
-				}
 		}
 
-			select {
-			default:
 		ids, err := s.by(ctxt, h, root)
-				if err == nil && len(ids) >= s.exp {
+		if err != nil || len(ids) < s.exp {
-					nodes, err := s.wait(ctxt, h, root, ids...)
+			return false
-					if err == nil {
-						if s.after == nil {
-							return
 		}
-
+		nodes, err := s.wait(ctxt, h, cur, ids...)
+		// if nodes==nil, we're not yet ready
+		if nodes == nil || err != nil {
+			return false
+		}
+		if s.after != nil {
 			if err := s.after(ctxt, h, nodes...); err != nil {
 				ch <- err
 			}
-						return
 		}
+		close(ch)
+		return true
 	}
-
-				time.Sleep(DefaultCheckDuration)
-
-			case <-root.Invalidated:
-				continue
-
-			case <-ctxt.Done():
-				ch <- ctxt.Err()
-				return
-			}
-		}
-	}()
-
 	return ch
 }
 
@@ -151,7 +128,7 @@ func (s *Selector) selAsString() string {
 // QueryAfter is an action that will match the specified sel using the supplied
 // query options, and after the visibility conditions of the query have been
 // met, will execute f.
-func QueryAfter(sel interface{}, f func(context.Context, *TargetHandler, ...*cdp.Node) error, opts ...QueryOption) Action {
+func QueryAfter(sel interface{}, f func(context.Context, *Target, ...*cdp.Node) error, opts ...QueryOption) Action {
 	return Query(sel, append(opts, After(f))...)
 }
 
@@ -159,7 +136,7 @@ func QueryAfter(sel interface{}, f func(context.Context, *TargetHandler, ...*cdp
 type QueryOption func(*Selector)
 
 // ByFunc is a query option to set the func used to select elements.
-func ByFunc(f func(context.Context, *TargetHandler, *cdp.Node) ([]cdp.NodeID, error)) QueryOption {
+func ByFunc(f func(context.Context, *Target, *cdp.Node) ([]cdp.NodeID, error)) QueryOption {
 	return func(s *Selector) {
 		s.by = f
 	}
@@ -168,7 +145,7 @@ func ByFunc(f func(context.Context, *TargetHandler, *cdp.Node) ([]cdp.NodeID, er
 // ByQuery is a query option to select a single element using
 // DOM.querySelector.
 func ByQuery(s *Selector) {
-	ByFunc(func(ctxt context.Context, h *TargetHandler, n *cdp.Node) ([]cdp.NodeID, error) {
+	ByFunc(func(ctxt context.Context, h *Target, n *cdp.Node) ([]cdp.NodeID, error) {
 		nodeID, err := dom.QuerySelector(n.NodeID, s.selAsString()).Do(ctxt, h)
 		if err != nil {
 			return nil, err
@@ -184,7 +161,7 @@ func ByQuery(s *Selector) {
 
 // ByQueryAll is a query option to select elements by DOM.querySelectorAll.
 func ByQueryAll(s *Selector) {
-	ByFunc(func(ctxt context.Context, h *TargetHandler, n *cdp.Node) ([]cdp.NodeID, error) {
+	ByFunc(func(ctxt context.Context, h *Target, n *cdp.Node) ([]cdp.NodeID, error) {
 		return dom.QuerySelectorAll(n.NodeID, s.selAsString()).Do(ctxt, h)
 	})(s)
 }
@@ -198,7 +175,7 @@ func ByID(s *Selector) {
 // BySearch is a query option via DOM.performSearch (works with both CSS and
 // XPath queries).
 func BySearch(s *Selector) {
-	ByFunc(func(ctxt context.Context, h *TargetHandler, n *cdp.Node) ([]cdp.NodeID, error) {
+	ByFunc(func(ctxt context.Context, h *Target, n *cdp.Node) ([]cdp.NodeID, error) {
 		id, count, err := dom.PerformSearch(s.selAsString()).Do(ctxt, h)
 		if err != nil {
 			return nil, err
@@ -224,7 +201,7 @@ func ByNodeID(s *Selector) {
 		panic("ByNodeID can only work on []cdp.NodeID")
 	}
 
-	ByFunc(func(ctxt context.Context, h *TargetHandler, n *cdp.Node) ([]cdp.NodeID, error) {
+	ByFunc(func(ctxt context.Context, h *Target, n *cdp.Node) ([]cdp.NodeID, error) {
 		for _, id := range ids {
 			err := dom.RequestChildNodes(id).WithPierce(true).Do(ctxt, h)
 			if err != nil {
@@ -237,32 +214,22 @@ func ByNodeID(s *Selector) {
 }
 
 // waitReady waits for the specified nodes to be ready.
-func (s *Selector) waitReady(check func(context.Context, *TargetHandler, *cdp.Node) error) func(context.Context, *TargetHandler, *cdp.Node, ...cdp.NodeID) ([]*cdp.Node, error) {
+func (s *Selector) waitReady(check func(context.Context, *Target, *cdp.Node) error) func(context.Context, *Target, *cdp.Frame, ...cdp.NodeID) ([]*cdp.Node, error) {
-	return func(ctxt context.Context, h *TargetHandler, n *cdp.Node, ids ...cdp.NodeID) ([]*cdp.Node, error) {
+	return func(ctxt context.Context, h *Target, cur *cdp.Frame, ids ...cdp.NodeID) ([]*cdp.Node, error) {
-		f, err := h.WaitFrame(ctxt, cdp.EmptyFrameID)
-		if err != nil {
-			return nil, err
-		}
-
-		wg := new(sync.WaitGroup)
 		nodes := make([]*cdp.Node, len(ids))
-		errs := make([]error, len(ids))
+		cur.RLock()
 		for i, id := range ids {
-			wg.Add(1)
+			nodes[i] = cur.Nodes[id]
-			go func(i int, id cdp.NodeID) {
+			if nodes[i] == nil {
-				defer wg.Done()
+				cur.RUnlock()
-				nodes[i], errs[i] = h.WaitNode(ctxt, f, id)
+				// not yet ready
-			}(i, id)
+				return nil, nil
-		}
-		wg.Wait()
-
-		for _, err := range errs {
-			if err != nil {
-				return nil, err
 			}
 		}
+		cur.RUnlock()
 
 		if check != nil {
+			var wg sync.WaitGroup
 			errs := make([]error, len(nodes))
 			for i, n := range nodes {
 				wg.Add(1)
@@ -285,7 +252,7 @@ func (s *Selector) waitReady(check func(context.Context, *TargetHandler, *cdp.No
 }
 
 // WaitFunc is a query option to set a custom wait func.
-func WaitFunc(wait func(context.Context, *TargetHandler, *cdp.Node, ...cdp.NodeID) ([]*cdp.Node, error)) QueryOption {
+func WaitFunc(wait func(context.Context, *Target, *cdp.Frame, ...cdp.NodeID) ([]*cdp.Node, error)) QueryOption {
 	return func(s *Selector) {
 		s.wait = wait
 	}
@@ -298,7 +265,7 @@ func NodeReady(s *Selector) {
 
 // NodeVisible is a query option to wait until the element is visible.
 func NodeVisible(s *Selector) {
-	WaitFunc(s.waitReady(func(ctxt context.Context, h *TargetHandler, n *cdp.Node) error {
+	WaitFunc(s.waitReady(func(ctxt context.Context, h *Target, n *cdp.Node) error {
 		// check box model
 		_, err := dom.GetBoxModel().WithNodeID(n.NodeID).Do(ctxt, h)
 		if err != nil {
@@ -324,7 +291,7 @@ func NodeVisible(s *Selector) {
 
 // NodeNotVisible is a query option to wait until the element is not visible.
 func NodeNotVisible(s *Selector) {
-	WaitFunc(s.waitReady(func(ctxt context.Context, h *TargetHandler, n *cdp.Node) error {
+	WaitFunc(s.waitReady(func(ctxt context.Context, h *Target, n *cdp.Node) error {
 		// check box model
 		_, err := dom.GetBoxModel().WithNodeID(n.NodeID).Do(ctxt, h)
 		if err != nil {
@@ -350,7 +317,7 @@ func NodeNotVisible(s *Selector) {
 
 // NodeEnabled is a query option to wait until the element is enabled.
 func NodeEnabled(s *Selector) {
-	WaitFunc(s.waitReady(func(ctxt context.Context, h *TargetHandler, n *cdp.Node) error {
+	WaitFunc(s.waitReady(func(ctxt context.Context, h *Target, n *cdp.Node) error {
 		n.RLock()
 		defer n.RUnlock()
 
@@ -366,7 +333,7 @@ func NodeEnabled(s *Selector) {
 
 // NodeSelected is a query option to wait until the element is selected.
 func NodeSelected(s *Selector) {
-	WaitFunc(s.waitReady(func(ctxt context.Context, h *TargetHandler, n *cdp.Node) error {
+	WaitFunc(s.waitReady(func(ctxt context.Context, h *Target, n *cdp.Node) error {
 		n.RLock()
 		defer n.RUnlock()
 
@@ -380,11 +347,11 @@ func NodeSelected(s *Selector) {
 	}))(s)
 }
 
-// NodeNotPresent is a query option to wait until no elements match are
+// NodeNotPresent is a query option to wait until no elements are present
-// present matching the selector.
+// matching the selector.
 func NodeNotPresent(s *Selector) {
 	s.exp = 0
-	WaitFunc(func(ctxt context.Context, h *TargetHandler, n *cdp.Node, ids ...cdp.NodeID) ([]*cdp.Node, error) {
+	WaitFunc(func(ctxt context.Context, h *Target, cur *cdp.Frame, ids ...cdp.NodeID) ([]*cdp.Node, error) {
 		if len(ids) != 0 {
 			return nil, ErrHasResults
 		}
@@ -402,7 +369,7 @@ func AtLeast(n int) QueryOption {
 
 // After is a query option to set a func that will be executed after the wait
 // has succeeded.
-func After(f func(context.Context, *TargetHandler, ...*cdp.Node) error) QueryOption {
+func After(f func(context.Context, *Target, ...*cdp.Node) error) QueryOption {
 	return func(s *Selector) {
 		s.after = f
 	}