convert javascript snippets to standalone embedded js files (part 1)

call.go

@@ -0,0 +1,88 @@
+package chromedp
+
+import (
+	"context"
+	"encoding/json"
+
+	"github.com/chromedp/cdproto/runtime"
+)
+
+// CallAction are actions that calls a Javascript function using
+// runtime.CallFunctionOn.
+type CallAction Action
+
+// CallFunctionOn is an action to call a Javascript function, unmarshaling
+// the result of the function to res.
+//
+// The handling of res is the same as that of Evaluate.
+//
+// Do not call the following methods on runtime.CallFunctionOnParams:
+// - WithReturnByValue: it will be set depending on the type of res;
+// - WithArguments: pass the arguments with args instead.
+//
+// Note: any exception encountered will be returned as an error.
+func CallFunctionOn(functionDeclaration string, res interface{}, opt CallOption, args ...interface{}) CallAction {
+	return ActionFunc(func(ctx context.Context) error {
+		// set up parameters
+		p := runtime.CallFunctionOn(functionDeclaration).
+			WithSilent(true)
+
+		switch res.(type) {
+		case nil, **runtime.RemoteObject:
+		default:
+			p = p.WithReturnByValue(true)
+		}
+
+		// apply opt
+		if opt != nil {
+			p = opt(p)
+		}
+
+		// arguments
+		if len(args) > 0 {
+			ea := &errAppender{args: make([]*runtime.CallArgument, 0, len(args))}
+			for _, arg := range args {
+				ea.append(arg)
+			}
+			if ea.err != nil {
+				return ea.err
+			}
+			p = p.WithArguments(ea.args)
+		}
+
+		// call
+		v, exp, err := p.Do(ctx)
+		if err != nil {
+			return err
+		}
+		if exp != nil {
+			return exp
+		}
+
+		return parseRemoteObject(v, res)
+	})
+}
+
+// CallOption is a function to modify the runtime.CallFunctionOnParams
+// to provide more information.
+type CallOption = func(params *runtime.CallFunctionOnParams) *runtime.CallFunctionOnParams
+
+// errAppender is to help accumulating the arguments and simplifying error checks.
+//
+// see https://blog.golang.org/errors-are-values
+type errAppender struct {
+	args []*runtime.CallArgument
+	err  error
+}
+
+// append method calls the json.Marshal method to marshal the value and appends it to the slice.
+// It records the first error for future reference.
+// As soon as an error occurs, the append method becomes a no-op but the error value is saved.
+func (ea *errAppender) append(v interface{}) {
+	if ea.err != nil {
+		return
+	}
+	var b []byte
+	b, ea.err = json.Marshal(v)
+	ea.args = append(ea.args, &runtime.CallArgument{Value: b})
+}

eval.go

@@ -15,26 +15,31 @@ type EvaluateAction Action
 // Evaluate is an action to evaluate the Javascript expression, unmarshaling
 // the result of the script evaluation to res.
 //
-// When res is a type other than *[]byte, or **runtime.RemoteObject,
-// then the result of the script evaluation will be returned "by value" (ie,
+// When res is nil, the script result will be ignored.
+//
+// When res is a *[]byte, the raw JSON-encoded value of the script
+// result will be placed in res.
+//
+// When res is a **runtime.RemoteObject, res will be set to the low-level
+// protocol type, and no attempt will be made to convert the result.
+// Original objects are maintained in memory until the page navigated or closed,
+// unless they are either explicitly released or are released along with the
+// other objects in their object group. runtime.ReleaseObject or
+// runtime.ReleaseObjectGroup can be used to ask the browser to release
+// original objects.
+//
+// For all other cases, the result of the script will be returned "by value" (ie,
 // JSON-encoded), and subsequently an attempt will be made to json.Unmarshal
 // the script result to res. It returns an error if the script result is
 // "undefined" in this case.
 //
-// Otherwise, when res is a *[]byte, the raw JSON-encoded value of the script
-// result will be placed in res. Similarly, if res is a **runtime.RemoteObject,
-// then res will be set to the low-level protocol type, and no attempt will be
-// made to convert the result. "undefined" is okay in this case.
-//
-// When res is nil, the script result will be ignored (including "undefined").
-//
 // Note: any exception encountered will be returned as an error.
 func Evaluate(expression string, res interface{}, opts ...EvaluateOption) EvaluateAction {
 	return ActionFunc(func(ctx context.Context) error {
 		// set up parameters
 		p := runtime.Evaluate(expression)
 		switch res.(type) {
-		case nil, **runtime.RemoteObject:
+		case **runtime.RemoteObject:
 		default:
 			p = p.WithReturnByValue(true)
 		}
@@ -53,30 +58,34 @@ func Evaluate(expression string, res interface{}, opts ...EvaluateOption) Evalua
 			return exp
 		}
 
-		if res == nil {
-			return nil
-		}
+		return parseRemoteObject(v, res)
+	})
+}
 
-		switch x := res.(type) {
-		case **runtime.RemoteObject:
-			*x = v
-			return nil
+func parseRemoteObject(v *runtime.RemoteObject, res interface{}) error {
+	if res == nil {
+		return nil
+	}
 
-		case *[]byte:
-			*x = []byte(v.Value)
-			return nil
-		}
+	switch x := res.(type) {
+	case **runtime.RemoteObject:
+		*x = v
+		return nil
 
-		if v.Type == "undefined" {
-			// The unmarshal above would fail with the cryptic
-			// "unexpected end of JSON input" error, so try to give
-			// a better one here.
-			return fmt.Errorf("encountered an undefined value")
-		}
+	case *[]byte:
+		*x = v.Value
+		return nil
+	}
 
-		// unmarshal
-		return json.Unmarshal(v.Value, res)
-	})
+	if v.Type == "undefined" {
+		// The unmarshal below would fail with the cryptic
+		// "unexpected end of JSON input" error, so try to give
+		// a better one here.
+		return fmt.Errorf("encountered an undefined value")
+	}
+
+	// unmarshal
+	return json.Unmarshal(v.Value, res)
 }
 
 // EvaluateAsDevTools is an action that evaluates a Javascript expression as

input.go

@@ -60,14 +60,8 @@ func MouseClickNode(n *cdp.Node, opts ...MouseOption) MouseAction {
 		if t == nil {
 			return ErrInvalidTarget
 		}
-		frameID := t.enclosingFrame(n)
-		t.frameMu.RLock()
-		execCtx := t.execContexts[frameID]
-		t.frameMu.RUnlock()
 
-		var pos []float64
-		err := evalInCtx(ctx, execCtx, snippet(scrollIntoViewJS, cashX(true), nil, n), &pos)
-		if err != nil {
+		if err := dom.ScrollIntoViewIfNeeded().WithNodeID(n.NodeID).Do(ctx); err != nil {
 			return err
 		}
 

js.go

@@ -1,97 +1,76 @@
 package chromedp
 
-import (
-	"fmt"
-
-	"github.com/chromedp/cdproto/cdp"
-)
-
 const (
-	// textJS is a javascript snippet that returns the concatenated innerText of all
-	// visible (ie, offsetWidth || offsetHeight || getClientRects().length ) children.
-	textJS = `(function(a) {
-		var s = '';
-		for (var i = 0; i < a.length; i++) {
-			if (a[i].offsetWidth || a[i].offsetHeight || a[i].getClientRects().length) {
-				s += a[i].innerText;
-			}
+	// textJS is a javascript snippet that returns the innerText of the specified
+	// visible (ie, offsetWidth || offsetHeight || getClientRects().length ) element.
+	textJS = `function text() {
+		if (this.offsetWidth || this.offsetHeight || this.getClientRects().length) {
+			return this.innerText;
 		}
-		return s;
-	})(%s)`
+		return '';
+	}`
 
-	// textContentJS is a javascript snippet that returns the concatenated textContent
-	// of all children.
-	textContentJS = `(function(a) {
-		var s = '';
-		for (var i = 0; i < a.length; i++) {
-			s += a[i].textContent;
-		}
-		return s;
-	})(%s)`
+	// textContentJS is a javascript snippet that returns the textContent of the
+	// specified element.
+	textContentJS = `function textContent() {
+		return this.textContent;
+	}`
 
 	// blurJS is a javascript snippet that blurs the specified element.
-	blurJS = `(function(a) {
-		a.blur();
+	blurJS = `function blur() {
+		this.blur();
 		return true;
-	})(%s)`
-
-	// scrollIntoViewJS is a javascript snippet that scrolls the specified node
-	// into the window's viewport (if needed), returning the actual window x/y
-	// after execution.
-	scrollIntoViewJS = `(function(a) {
-		a.scrollIntoViewIfNeeded(true);
-		return [window.scrollX, window.scrollY];
-	})(%s)`
+	}`
 
 	// submitJS is a javascript snippet that will call the containing form's
 	// submit function, returning true or false if the call was successful.
-	submitJS = `(function(a) {
-		if (a.nodeName === 'FORM') {
-			HTMLFormElement.prototype.submit.call(a);
+	submitJS = `function submit() {
+		if (this.nodeName === 'FORM') {
+			HTMLFormElement.prototype.submit.call(this);
 			return true;
-		} else if (a.form !== null) {
-			HTMLFormElement.prototype.submit.call(a.form);
+		} else if (this.form !== null) {
+			HTMLFormElement.prototype.submit.call(this.form);
 			return true;
 		}
 		return false;
-	})(%s)`
+	}`
 
 	// resetJS is a javascript snippet that will call the containing form's
 	// reset function, returning true or false if the call was successful.
-	resetJS = `(function(a) {
-		if (a.nodeName === 'FORM') {
-			HTMLFormElement.prototype.reset.call(a);
+	resetJS = `function reset() {
+		if (this.nodeName === 'FORM') {
+			HTMLFormElement.prototype.reset.call(this);
 			return true;
-		} else if (a.form !== null) {
-			HTMLFormElement.prototype.reset.call(a.form);
+		} else if (this.form !== null) {
+			HTMLFormElement.prototype.reset.call(this.form);
 			return true;
 		}
 		return false;
-	})(%s)`
+	}`
 
 	// attributeJS is a javascript snippet that returns the attribute of a specified
 	// node.
-	attributeJS = `(function(a, n) {
-		return a[n];
-	})(%s, %q)`
+	attributeJS = `function attribute(n) {
+		return this[n];
+	}`
 
 	// setAttributeJS is a javascript snippet that sets the value of the specified
 	// node, and returns the value.
-	setAttributeJS = `(function(a, n, v) {
-		a[n] = v;
+	setAttributeJS = `function setAttribute(n, v) {
+		this[n] = v;
 		if (n === 'value') {
-			a.dispatchEvent(new Event('input', { bubbles: true }));
-			a.dispatchEvent(new Event('change', { bubbles: true }));
+			this.dispatchEvent(new Event('input', { bubbles: true }));
+			this.dispatchEvent(new Event('change', { bubbles: true }));
 		}
-		return a[n];
-	})(%s, %q, %q)`
+		return this[n];
+	}`
 
 	// visibleJS is a javascript snippet that returns true or false depending on if
 	// the specified node's offsetWidth, offsetHeight or getClientRects().length is
 	// not null.
-	visibleJS = `(function(a) {
-		return Boolean( a.offsetWidth || a.offsetHeight || a.getClientRects().length );
-	})(%s)`
+	visibleJS = `function visible() {
+		return Boolean( this.offsetWidth || this.offsetHeight || this.getClientRects().length );
+	}`
 
 	// waitForPredicatePageFunction is a javascript snippet that runs the polling in the
 	// browser. It's copied from puppeteer. See
@@ -176,34 +155,3 @@ const (
 		}
 	}`
 )
-
-// snippet builds a Javascript expression snippet.
-func snippet(js string, f func(n *cdp.Node) string, sel interface{}, n *cdp.Node, v ...interface{}) string {
-	switch s := sel.(type) {
-	case *Selector:
-		if s != nil && s.raw {
-			return fmt.Sprintf(js, append([]interface{}{s.selAsString()}, v...)...)
-		}
-	}
-	return fmt.Sprintf(js, append([]interface{}{f(n)}, v...)...)
-}
-
-// cashX returns the $x() expression using the node's full xpath value.
-func cashX(flatten bool) func(*cdp.Node) string {
-	return func(n *cdp.Node) string {
-		if flatten {
-			return fmt.Sprintf(`$x(%q)[0]`, n.PartialXPath())
-		}
-		return fmt.Sprintf(`$x(%q)`, n.PartialXPath())
-	}
-}
-
-// cashXNode returns the $x(/node()) expression using the node's full xpath value.
-func cashXNode(flatten bool) func(*cdp.Node) string {
-	return func(n *cdp.Node) string {
-		if flatten {
-			return fmt.Sprintf(`$x(%q)[0]`, n.PartialXPath()+"/node()")
-		}
-		return fmt.Sprintf(`$x(%q)`, n.PartialXPath()+"/node()")
-	}
-}