sdbbs sdbbs - 5 months ago 69
Javascript Question

casperjs/slimerjs invalid selector in waitForSelector, which works in getElementByXPath?

I have this HTML file,

test_xpath.htm
:

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
</head>

<body>
<h1>Hello World!</h1>
<div>
<a href="http://stackoverflow.com">Click me!</a>
</div>
</body>
</html>


In the folder of this file, I run PHP CLI > 5.4 as a server like this:

php -S localhost:8080


... so the HTML page is available at
http://localhost:8080/test_xpath.htm
.

Then I run this SlimerJS code:

// run with:
// SLIMERJSLAUNCHER=/usr/bin/firefox46 /home/USERNAME/.nvm/versions/node/v4.0.0/lib/node_modules/casperjs/bin/casperjs --engine=slimerjs test_xpath.js

var casper = require('casper').create({
verbose: true,
logLevel: 'debug',
userAgent: 'Mozilla/5.0 (X11; Linux i686; rv:43.0) Gecko/20100101 Firefox/43.0',
viewportSize: {width: 1024, height: 768},
pageSettings: {
loadImages: false,//The script is much faster when this field is set to false
loadPlugins: false,
}
});

casper.on("url.changed", function(){
this.then(function(){
this.echo("URL changed " + this.getCurrentUrl()); //getTitle());
});
});

casper.on('remote.message', function(message) {
this.echo('remote message caught: ' + message);
});

casper.start().thenOpen("http://localhost:8080/test_xpath.htm", function() {
console.log("website opened");
});

// set this to true to run - causes "[error] [remote] findAll(): invalid selector provided "//*[text()="Click me!"]":SyntaxError: An invalid or illegal string was specified"
if (false) {
casper.waitForSelector('//*[text()="Click me!"]', function() {
this.echo("I'm sure //*[text()='Click me!'] is available in the DOM");
});
}

casper.then(function(){
this.evaluate(function(){
var aelem = __utils__.getElementByXPath('//*[text()="Click me!"]');
aelem.click();
});
});


casper.then(function(){
casper.capture('TestCapture.png');
});

casper.run();


If I run the JS code as is - that is, the
waitForSelector
part is disabled by
if(false)
- then everything runs fine.

However, if I enable that part by changing the
if(false)
to
if(true)
, I get this:

$ SLIMERJSLAUNCHER=/usr/bin/firefox46 /home/USERNAME/.nvm/versions/node/v4.0.0/lib/node_modules/casperjs/bin/casperjs --engine=slimerjs test_xpath.js
[info] [phantom] Starting...
[info] [phantom] Running suite: 5 steps
[debug] [phantom] opening url: http://localhost:8080/test_xpath.htm, HTTP GET
[debug] [phantom] Navigation requested: url=http://localhost:8080/test_xpath.htm, type=Undefined, willNavigate=true, isMainFrame=true
[debug] [phantom] url changed to "http://localhost:8080/test_xpath.htm"
[debug] [phantom] Successfully injected Casper client-side utilities
[info] [phantom] Step anonymous 2/6 http://localhost:8080/test_xpath.htm (HTTP 200)
URL changed http://localhost:8080/test_xpath.htm
[info] [phantom] Step anonymous 2/6: done in 235ms.
[info] [phantom] Step anonymous 3/6 http://localhost:8080/test_xpath.htm (HTTP 200)
website opened
[info] [phantom] Step anonymous 3/6: done in 258ms.
[info] [phantom] Step _step 4/6 http://localhost:8080/test_xpath.htm (HTTP 200)
[info] [phantom] Step _step 4/6: done in 276ms.
[error] [remote] findAll(): invalid selector provided "//*[text()="Click me!"]":SyntaxError: An invalid or illegal string was specified
[error] [remote] findAll(): invalid selector provided "//*[text()="Click me!"]":SyntaxError: An invalid or illegal string was specified
[error] [remote] findAll(): invalid selector provided "//*[text()="Click me!"]":SyntaxError: An invalid or illegal string was specified
[error] [remote] findAll(): invalid selector provided "//*[text()="Click me!"]":SyntaxError: An invalid or illegal string was specified
[error] [remote] findAll(): invalid selector provided "//*[text()="Click me!"]":SyntaxError: An invalid or illegal string was specified
....


I truly don't understand this, because http://docs.casperjs.org/en/latest/modules/casper.html#waitforselector says:


Waits until an element matching the provided selector expression exists in remote DOM to process any next step


... where http://docs.casperjs.org/en/latest/selectors.html says:


CasperJS makes a heavy use of selectors in order to work with the DOM, and can transparently use either CSS3 or XPath expressions.


So, XPath should be OK - what's more, I'm using THE EXACT SAME XPATH in:

var aelem = __utils__.getElementByXPath('//*[text()="Click me!"]');


... and there it works, but it fails in:

casper.waitForSelector('//*[text()="Click me!"]', function() { ....


Why does this happen - where am I going wrong? And how can I use this XPath in
waitForSelector
, if it's possible?

Answer

If you pass a string into the waitForSelector() function, it would be interpreted as a CSS selector. To have it work with an XPath expression pass in an object explicitly specifying the selector type:

selectorObject = {
  type: 'xpath',
  path: '//*[text()="Click me!"]'
}
casper.waitForSelector(selectorObject, function() {
  // ...
});

You can solve it with waitForText() as well, sample here.