waitForSelector 通过,但 assertExists 对同一个选择器失败
当我调用以下函数时,waitForSelector
为选择器"传递,但 assertExists
对同一选择器失败.怎么可能?
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);
这里是使用 :nth-child 重现问题的完整示例
选择器.
推荐答案
这是一个已知的错误(参见 #11632,#11737)在 WebKit 的 Qt4 分支中(来自2010).当使用 :nth-child()
或 :nth-of-type()
CSS3 选择器时会发生这种情况.选择器第二次运行时,它返回不同的结果(大部分时间是 null
).唯一已知的解决方法是使用 XPath 表达式而不是 CSS3 选择器.此错误已在 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).
这是在 http://example.com 上重现问题的最小脚本(修改自 这里):
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:
标记是:
Markup is:
<h1>文本</h1><p>文本</p><p><a href="url">文本</a></p></div>
<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.通常人们会写 //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
.
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