问题描述
当我调用下面的函数时, waitForSelector
传递给'selector',但 assertExists
。如何实现?
When I call the following function, waitForSelector
passes for 'selector', but assertExists
fails for the same selector. How is it possible?
casper.waitForSelector(selector, function() {
casper.test.assertExists(selector, sectionName + " opened up successfully.");
}, function() {
casper.test.fail(sectionName + " did not load in given time");
}, max_timeout);
是用:nth-child
选择器重现问题的完整示例。
Here is a complete example to reproduce the issue with an :nth-child
selector.
推荐答案
这是已知的错误(请参阅,)在WebKit的Qt4分支(从2010年)。当:nth-child()
或:nth-of-type()
时,会使用CSS3选择器。第二次运行选择器时,返回不同的结果(大部分时间 null
)。唯一已知的解决方法是使用XPath表达式而不是CSS3选择器。这个bug在PhantomJS 2中修复,因为它使用WebKit的Qt5分支(版本538.1)。
This is a known bug (see #11632, #11737) in the Qt4 fork of WebKit (from 2010). It happens when :nth-child()
or :nth-of-type()
CSS3 selectors are used. The second time the selector is run, it returns a different result (most of the time null
). The only known workaround is to use XPath expressions instead of CSS3 selectors. This bug is fixed in PhantomJS 2 as it uses a Qt5 fork of WebKit (version 538.1).
这是一个最小的脚本来重现(修改自):
This is a minimal script to reproduce the issue on http://example.com (modified from here):
var casper = require('casper').create(),
x = require('casper').selectXPath;
casper.start('http://example.com', function() {
var selector = 'p:nth-child(3) > a',
xpSelector = '//*[local-name()="p" and position()=3]/a';
var first = this.exists(selector);
var second = this.exists(selector);
if(first !== second) {
console.error('Expected First selector to equal the Second');
} else {
console.log('Passed');
}
first = this.exists(x(xpSelector));
second = this.exists(x(xpSelector));
if(first !== second) {
console.error('Expected First selector to equal the Second');
} else {
console.log('Passed');
}
}).run();
输出:
Expected First selector to equal the Second
Passed
标记是:
<div>
<h1>text</h1>
<p>text</p>
<p><a href="url">text</a></p>
</div>
XPath表达式看起来有点尴尬,因为它直接再现了CSS选择器的预期行为。通常会写 // p [2] / a
。
The XPath expression looks a little awkward, because it directly reproduces the intended behavior of the CSS selector. Normally one would write //p[2]/a
.
这篇关于waitForSelector传递,但assertExists对同一个选择器失败的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持!