casperjs/slimerjs 在 getElementByXPath 中有效的 waitForSelector 中的选择器无效？

Question

我有这个 HTML 文件，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://whosebug.com">Click me!</a>
  </div>
</body>
</html>

在这个文件的文件夹中，我运行 PHP CLI > 5.4 作为服务器是这样的：

php -S localhost:8080

...因此 HTML 页面可在 http://localhost:8080/test_xpath.htm.

然后我运行这个 SlimerJS 代码：

// 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();

如果我运行 JS 代码原样 - 即 waitForSelector 部分被 if(false) 禁用 - 那么一切运行都很好。

但是，如果我通过将 if(false) 更改为 if(true) 来启用该部分，我会得到：

$ 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 
....

我真的不明白，因为http://docs.casperjs.org/en/latest/modules/casper.html#waitforselector说：

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

... 其中 http://docs.casperjs.org/en/latest/selectors.html 表示：

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

所以，XPath 应该没问题 - 而且，我正在使用 完全相同的 XPATH 在：

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

...在那里它可以工作，但它失败了：

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

为什么会这样——我哪里出错了？如果可能的话，我如何在 waitForSelector 中使用这个 XPath？

Answer 1

如果将字符串传递给 waitForSelector() 函数，它将被解释为 CSS 选择器 。要让它与 XPath 表达式一起工作，传入 object 显式指定选择器 type:

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

你也可以用waitForText()解决，示例。

casperjs/slimerjs 在 getElementByXPath 中有效的 waitForSelector 中的选择器无效？

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

javascript

xpath

casperjs

slimerjs