simplify the design of js helper

dev_helpers.go

@@ -103,7 +103,7 @@ func (b *Browser) trySlowmotion() {
 
 // ExposeHelpers helper functions to page's js context so that we can use the Devtools' console to debug them.
 func (p *Page) ExposeHelpers(list ...*js.Function) {
-	p.MustEvaluate(EvalHelper(&js.Function{
+	p.MustEvaluate(evalHelper(&js.Function{
 		Name:         "_" + utils.RandString(8), // use a random name so it won't hit the cache
 		Definition:   "() => { window.rod = functions }",
 		Dependencies: list,
@@ -114,7 +114,7 @@ func (p *Page) ExposeHelpers(list ...*js.Function) {
 func (p *Page) Overlay(left, top, width, height float64, msg string) (remove func()) {
 	id := utils.RandString(8)
 
-	_, _ = p.root.Evaluate(EvalHelper(js.Overlay,
+	_, _ = p.root.Evaluate(evalHelper(js.Overlay,
 		id,
 		left,
 		top,
@@ -124,7 +124,7 @@ func (p *Page) Overlay(left, top, width, height float64, msg string) (remove fun
 	).ByPromise())
 
 	remove = func() {
-		_, _ = p.root.Evaluate(EvalHelper(js.RemoveOverlay, id))
+		_, _ = p.root.Evaluate(evalHelper(js.RemoveOverlay, id))
 	}
 
 	return
@@ -198,13 +198,13 @@ func (p *Page) tryTraceReq(includes, excludes []string) func(map[proto.NetworkRe
 func (el *Element) Overlay(msg string) (removeOverlay func()) {
 	id := utils.RandString(8)
 
-	_, _ = el.Evaluate(EvalHelper(js.ElementOverlay,
+	_, _ = el.Evaluate(evalHelper(js.ElementOverlay,
 		id,
 		msg,
 	).ByPromise())
 
 	removeOverlay = func() {
-		_, _ = el.Evaluate(EvalHelper(js.RemoveOverlay, id))
+		_, _ = el.Evaluate(evalHelper(js.RemoveOverlay, id))
 	}
 
 	return
@@ -224,11 +224,11 @@ func (el *Element) tryTrace(typ TraceType, msg ...interface{}) func() {
 }
 
 func (m *Mouse) initMouseTracer() {
-	_, _ = m.page.Evaluate(EvalHelper(js.InitMouseTracer, m.id, assets.MousePointer).ByPromise())
+	_, _ = m.page.Evaluate(evalHelper(js.InitMouseTracer, m.id, assets.MousePointer).ByPromise())
 }
 
 func (m *Mouse) updateMouseTracer() bool {
-	res, err := m.page.Evaluate(EvalHelper(js.UpdateMouseTracer, m.id, m.x, m.y))
+	res, err := m.page.Evaluate(evalHelper(js.UpdateMouseTracer, m.id, m.x, m.y))
 	if err != nil {
 		return true
 	}

element.go

@@ -220,7 +220,7 @@ func (el *Element) SelectText(regex string) error {
 	defer el.tryTrace(TraceTypeInput, "select text: "+regex)()
 	el.page.browser.trySlowmotion()
 
-	_, err = el.Evaluate(EvalHelper(js.SelectText, regex).ByUser())
+	_, err = el.Evaluate(evalHelper(js.SelectText, regex).ByUser())
 	return err
 }
 
@@ -235,7 +235,7 @@ func (el *Element) SelectAllText() error {
 	defer el.tryTrace(TraceTypeInput, "select all text")()
 	el.page.browser.trySlowmotion()
 
-	_, err = el.Evaluate(EvalHelper(js.SelectAllText).ByUser())
+	_, err = el.Evaluate(evalHelper(js.SelectAllText).ByUser())
 	return err
 }
 
@@ -270,7 +270,7 @@ func (el *Element) Input(text string) error {
 		return err
 	}
 
-	_, err = el.Evaluate(EvalHelper(js.InputEvent).ByUser())
+	_, err = el.Evaluate(evalHelper(js.InputEvent).ByUser())
 	return err
 }
 
@@ -300,7 +300,7 @@ func (el *Element) InputTime(t time.Time) error {
 
 	defer el.tryTrace(TraceTypeInput, "input "+t.String())()
 
-	_, err = el.Evaluate(EvalHelper(js.InputTime, t.UnixNano()/1e6).ByUser())
+	_, err = el.Evaluate(evalHelper(js.InputTime, t.UnixNano()/1e6).ByUser())
 	return err
 }
 
@@ -326,7 +326,7 @@ func (el *Element) Select(selectors []string, selected bool, t SelectorType) err
 	defer el.tryTrace(TraceTypeInput, fmt.Sprintf(`select "%s"`, strings.Join(selectors, "; ")))()
 	el.page.browser.trySlowmotion()
 
-	_, err = el.Evaluate(EvalHelper(js.Select, selectors, selected, t).ByUser())
+	_, err = el.Evaluate(evalHelper(js.Select, selectors, selected, t).ByUser())
 	return err
 }
 
@@ -436,7 +436,7 @@ func (el *Element) Frame() (*Page, error) {
 
 // ContainsElement check if the target is equal or inside the element.
 func (el *Element) ContainsElement(target *Element) (bool, error) {
-	res, err := el.Evaluate(EvalHelper(js.ContainsElement, target.Object))
+	res, err := el.Evaluate(evalHelper(js.ContainsElement, target.Object))
 	if err != nil {
 		return false, err
 	}
@@ -445,7 +445,7 @@ func (el *Element) ContainsElement(target *Element) (bool, error) {
 
 // Text that the element displays
 func (el *Element) Text() (string, error) {
-	str, err := el.Evaluate(EvalHelper(js.Text))
+	str, err := el.Evaluate(evalHelper(js.Text))
 	if err != nil {
 		return "", err
 	}
@@ -463,7 +463,7 @@ func (el *Element) HTML() (string, error) {
 
 // Visible returns true if the element is visible on the page
 func (el *Element) Visible() (bool, error) {
-	res, err := el.Evaluate(EvalHelper(js.Visible))
+	res, err := el.Evaluate(evalHelper(js.Visible))
 	if err != nil {
 		return false, err
 	}
@@ -473,7 +473,7 @@ func (el *Element) Visible() (bool, error) {
 // WaitLoad for element like <img>
 func (el *Element) WaitLoad() error {
 	defer el.tryTrace(TraceTypeWait, "load")()
-	_, err := el.Evaluate(EvalHelper(js.WaitLoad).ByPromise())
+	_, err := el.Evaluate(evalHelper(js.WaitLoad).ByPromise())
 	return err
 }
 
@@ -586,7 +586,7 @@ func (el *Element) Wait(opts *EvalOptions) error {
 // WaitVisible until the element is visible
 func (el *Element) WaitVisible() error {
 	defer el.tryTrace(TraceTypeWait, "visible")()
-	return el.Wait(EvalHelper(js.Visible))
+	return el.Wait(evalHelper(js.Visible))
 }
 
 // WaitEnabled until the element is not disabled.
@@ -606,7 +606,7 @@ func (el *Element) WaitWritable() error {
 // WaitInvisible until the element invisible
 func (el *Element) WaitInvisible() error {
 	defer el.tryTrace(TraceTypeWait, "invisible")()
-	return el.Wait(EvalHelper(js.Invisible))
+	return el.Wait(evalHelper(js.Invisible))
 }
 
 // CanvasToImage get image data of a canvas.
@@ -625,7 +625,7 @@ func (el *Element) CanvasToImage(format string, quality float64) ([]byte, error)
 
 // Resource returns the "src" content of current element. Such as the jpg of <img src="a.jpg">
 func (el *Element) Resource() ([]byte, error) {
-	src, err := el.Evaluate(EvalHelper(js.Resource).ByPromise())
+	src, err := el.Evaluate(evalHelper(js.Resource).ByPromise())
 	if err != nil {
 		return nil, err
 	}

page.go

@@ -516,7 +516,7 @@ func (p *Page) WaitRequestIdle(d time.Duration, includes, excludes []string) fun
 
 // WaitIdle waits until the next window.requestIdleCallback is called.
 func (p *Page) WaitIdle(timeout time.Duration) (err error) {
-	_, err = p.Evaluate(EvalHelper(js.WaitIdle, timeout.Seconds()).ByPromise())
+	_, err = p.Evaluate(evalHelper(js.WaitIdle, timeout.Seconds()).ByPromise())
 	return err
 }
 
@@ -531,23 +531,23 @@ func (p *Page) WaitRepaint() error {
 // WaitLoad waits for the `window.onload` event, it returns immediately if the event is already fired.
 func (p *Page) WaitLoad() error {
 	defer p.tryTrace(TraceTypeWait, "load")()
-	_, err := p.Evaluate(EvalHelper(js.WaitLoad).ByPromise())
+	_, err := p.Evaluate(evalHelper(js.WaitLoad).ByPromise())
 	return err
 }
 
 // AddScriptTag to page. If url is empty, content will be used.
 func (p *Page) AddScriptTag(url, content string) error {
 	hash := md5.Sum([]byte(url + content))
 	id := hex.EncodeToString(hash[:])
-	_, err := p.Evaluate(EvalHelper(js.AddScriptTag, id, url, content).ByPromise())
+	_, err := p.Evaluate(evalHelper(js.AddScriptTag, id, url, content).ByPromise())
 	return err
 }
 
 // AddStyleTag to page. If url is empty, content will be used.
 func (p *Page) AddStyleTag(url, content string) error {
 	hash := md5.Sum([]byte(url + content))
 	id := hex.EncodeToString(hash[:])
-	_, err := p.Evaluate(EvalHelper(js.AddStyleTag, id, url, content).ByPromise())
+	_, err := p.Evaluate(evalHelper(js.AddStyleTag, id, url, content).ByPromise())
 	return err
 }
 

page_eval.go

@@ -44,11 +44,13 @@ type EvalOptions struct {
 
 	// Whether execution should be treated as initiated by user in the UI.
 	UserGesture bool
-
-	jsHelper *js.Function
 }
 
 // Eval creates a EvalOptions with ByValue set to true.
+//
+// When an arg in the args is a *js.Function, the arg will be cached on the page's js context.
+// When the arg.Name exists in the page's cache, it reuse the cache without sending the definition to the browser again.
+// Useful when you need to eval a huge js expression many times.
 func Eval(js string, args ...interface{}) *EvalOptions {
 	return &EvalOptions{
 		ByValue:      true,
@@ -57,38 +59,35 @@ func Eval(js string, args ...interface{}) *EvalOptions {
 		JS:           js,
 		JSArgs:       args,
 		UserGesture:  false,
-		jsHelper:     nil,
 	}
 }
 
-// EvalHelper creates a special EvalOptions that will eval and cache the fn on the page's js context.
-// When the fn.Name exists in the page's cache, it reuse the cache without sending the definition to the browser again.
-// Useful when you need to eval a huge js expression many times.
-func EvalHelper(fn *js.Function, args ...interface{}) *EvalOptions {
+func evalHelper(fn *js.Function, args ...interface{}) *EvalOptions {
 	return &EvalOptions{
-		ByValue:  true,
-		JSArgs:   args,
-		JS:       `({fn}, ...args) => fn.apply(this, args)`,
-		jsHelper: fn,
+		ByValue: true,
+		JSArgs:  append([]interface{}{fn}, args...),
+		JS:      `(f, ...args) => f.apply(this, args)`,
 	}
 }
 
 // String interface
 func (e *EvalOptions) String() string {
 	fn := e.JS
-
-	if e.jsHelper != nil {
-		fn = "rod." + e.jsHelper.Name
-	}
+	args := e.JSArgs
 
 	paramsStr := ""
 	thisStr := ""
 
 	if e.ThisObj != nil {
 		thisStr = e.ThisObj.Description
 	}
-	if len(e.JSArgs) > 0 {
-		paramsStr = strings.Trim(mustToJSONForDev(e.JSArgs), "[]\r\n")
+	if len(args) > 0 {
+		if f, ok := args[0].(*js.Function); ok {
+			fn = "rod." + f.Name
+			args = e.JSArgs[1:]
+		}
+
+		paramsStr = strings.Trim(mustToJSONForDev(args), "[]\r\n")
 	}
 
 	return fmt.Sprintf("%s(%s) %s", fn, paramsStr, thisStr)
@@ -243,20 +242,17 @@ func (p *Page) formatArgs(opts *EvalOptions) ([]*proto.RuntimeCallArgument, erro
 	for _, arg := range opts.JSArgs {
 		if obj, ok := arg.(*proto.RuntimeRemoteObject); ok { // remote object
 			formated = append(formated, &proto.RuntimeCallArgument{ObjectID: obj.ObjectID})
+		} else if obj, ok := arg.(*js.Function); ok { // js helper
+			id, err := p.ensureJSHelper(obj)
+			if err != nil {
+				return nil, err
+			}
+			formated = append(formated, &proto.RuntimeCallArgument{ObjectID: id})
 		} else { // plain json data
 			formated = append(formated, &proto.RuntimeCallArgument{Value: gson.New(arg)})
 		}
 	}
 
-	if opts.jsHelper != nil {
-		id, err := p.ensureJSHelper(opts.jsHelper)
-		if err != nil {
-			return nil, err
-		}
-
-		formated = append([]*proto.RuntimeCallArgument{{ObjectID: id}}, formated...)
-	}
-
 	return formated, nil
 }
 
@@ -304,10 +300,10 @@ func (p *Page) ensureJSHelper(fn *js.Function) (proto.RuntimeRemoteObjectID, err
 			Arguments: []*proto.RuntimeCallArgument{{ObjectID: fns}},
 
 			FunctionDeclaration: fmt.Sprintf(
-				// We wrap an extra {fn: fn} here to reduce the response body size,
 				// we only need the object id, but the cdp will return the whole function string.
-				"functions => { functions.%s = %s; return { fn: functions.%s } }",
-				fn.Name, fn.Definition, fn.Name,
+				// So we override the toString to reduce the overhead.
+				"functions => { const f = functions.%s = %s; f.toString = () => 'fn'; return f }",
+				fn.Name, fn.Definition,
 			),
 		}.Call(p)
 		if err != nil {

page_eval_test.go

@@ -5,7 +5,6 @@ import (
 
 	"github.com/go-rod/rod"
 	"github.com/go-rod/rod/lib/cdp"
-	"github.com/go-rod/rod/lib/js"
 	"github.com/go-rod/rod/lib/proto"
 	"github.com/go-rod/rod/lib/utils"
 	"github.com/ysmood/gson"
@@ -237,7 +236,7 @@ func (t T) EnsureJSHelperErr() {
 	p := t.page.MustNavigate(t.blank())
 
 	t.mc.stubErr(2, proto.RuntimeCallFunctionOn{})
-	t.Err(p.Evaluate(rod.EvalHelper(js.Overlay, "test", 0, 0, 10, 10, "msg")))
+	t.Err(p.Elements(`button`))
 }
 
 func (t T) EvalOptionsString() {