javascript - CasperJS 中的静默错误

Question

我刚开始使用 CasperJs，我很难调试它，因为太多的编码错误似乎导致脚本在没有提供错误消息的情况下退出。当你使用详细模式时，你会得到你应该得到的消息，直到有问题的代码行，然后它就退出了。

例如，如果我执行代码:

var casper = require('casper').create({
    verbose: true,
    logLevel: "debug"
});

casper.start('https://www.google.com/#q=stackoverflow', function(){

});
casper.wait(2000, function(){
});


casper.then(function() {
    hrefAr = this.evaluate(getLinks);
    this.log(hrefAr.length + ' links found', 'info');
    this.exit();
});

casper.run(function() {
    this.exit();
});

function getLinks() {
    var links = document.querySelectorAll('a');
    return Array.prototype.map.call(links, function(e) {
        return e.getAttribute('href');
    });
}

我得到以下结果:

...a bunch of info & debug messages, followed by...
[info] [phantom] Step 4/4 https://www.google.com/search?q=stackoverflow&cad=h (HTTP 200)
[info] [phantom] 89 links found
[debug] [phantom] Navigation requested: url=about:blank, type=Other, lock=true, isMainFrame=true
[debug] [phantom] url changed to "about:blank"

如果我向函数 getLinks 添加一条日志语句...

...code as shown above...
function getLinks() {
    this.log('getLinks ran', 'info');
    var links = document.querySelectorAll('a');
...code as shown above...

...这会导致脚本失败，如下所示:

...the same info & debug messages...
[info] [phantom] Step 4/4 https://www.google.com/search?q=stackoverflow&cad=h (HTTP 200)
...NO LOGS, ECHOS, OR RESULTS PAST THIS POINT, JUST THESE TWO CLOSING STATEMENTS...
[debug] [phantom] Navigation requested: url=about:blank, type=Other, lock=true, isMainFrame=true
[debug] [phantom] url changed to "about:blank"

它不会告诉您出现任何问题，它只会让您返回空白并结束执行。

有没有办法获得更好的错误报告？或者任何错误报告？

---

当我尝试使用以下代码实现以下解决方法时:

var casper = require('casper').create({
    verbose: true,
    logLevel: "debug"
});

casper.start('https://www.google.com/#q=stackoverflow', function(){

});
casper.wait(2000, function(){
});


casper.then(function() {
    reportErrors(function() {
        hrefAr = this.evaluate(getLinks);
        this.log(hrefAr.length + ' links found', 'info');
        this.exit();
    });
});

casper.run(function() {
    this.exit();
});

function getLinks() {

        //this.log('getLinks ran', 'info');
        var links = document.querySelectorAll('a');
        return Array.prototype.map.call(links, function(e) {
            return e.getAttribute('href');
        });

}

function reportErrors(f) {
  var ret = null;
  try {
    ret = f();
  } catch (e) {
    casper.echo("ERROR: " + e);
    casper.exit();
  }
  return ret;
}

我明白了...

...info & debug messages shown above...
[info] [phantom] Step 4/4 https://www.google.com/search?q=stackoverflow&cad=h (HTTP 200)
ERROR: TypeError: undefined is not a constructor (evaluating 'this.evaluate(getLinks)') 
--THIS IS WHERE MY LINK COUNT WOULD BE REPORTED
[debug] [phantom] Navigation requested: url=about:blank, type=Other, lock=true, isMainFrame=true
[debug] [phantom] url changed to "about:blank"

Answer 1

有一个开放的PhantomJS issue对此。

你可以通过包装每个 then 和类似的 reportErrors 函数来绕过它，例如:

function reportErrors(f) {
  var ret = null;
  try {
    ret = f();
  } catch (e) {
    casper.echo("ERROR: " + e);
    casper.exit();
  }
  return ret;
}

casper.then(function() {
  reportErrors(function() {
    ...
  });
});