Question

我正在运行node.js和Selenium WebDriverJS。我的一个测试失败，出现以下错误：

UnknownError: unknown error: Runtime.evaluate threw exception: Error: element is not attached to the page document

据我所知，这实际上是一个StaleElementReferenceException，但我找不到可靠的解决方法。我没有成功尝试以下内容：

在找到并单击元素之前等待元素出现在页面上

waitForElement: function (selector, timeout) {
    if (typeof(timeout) === 'undefined') { timeout = 3000; }
    driver.wait(function() {
        return driver.findElements(selector).then(function(list) {
            return list.length > 0;
        });
    }, timeout);
}

在找到并点击元素之前等待明确的时间段（driver.sleep(1000)）
在点击元素

.findElement()

使用promise链捕获任何错误并尝试重新点击元素

driver.getTitle().then(function(title) {
    driver.findElement(webdriver.By.xpath(...)).click();
}).thenCatch(function(e) {
    driver.findElement(webdriver.By.xpath(...)).click();
});

使用具有递归函数的promise链继续尝试重新单击元素

var getStaleElement = function(selector, callback) {
    var element = driver.findElement(selector);
    callback(element);
}).thenCatch(function(e) {
    getStaleElement(selector, callback);
});

var clickSelf = function(ele) { return ele.click() };

driver.getTitle().then(function(title) {
    driver.findElement(webdriver.By.xpath(...)).click();
}).thenCatch(function(e) {
    getStaleElement(webdriver.By.xpath(...), clickSelf);
});

方法4和5使用.then()的错误参数代替.thenCatch()
上述

似乎Selenium无法捕获此特定错误。我使用print语句来确认.thenCatch()捕获了其他错误，例如NoSuchElementError。是否有一种解决方法可以让我处理过时的元素？

Answer 1

我遇到了类似的问题，所以我做了下面的解决方法，你可以尝试一下......

/*
 * params.config - {
 *           opposite - {Boolean} - if true, will wait till negative result is reached/ error is thrown.
 *           maxWaitTime - {Number} - if this time exceeds, just throw an error and leave.
 *           waitTime - {Number} - wait time between two checks.
 *           expectValue - {Boolean} - where you just want it to run without error, or it should expect a value
 *           expectedValue - {Object} - object value it should or should not match.
 *         }
 *  params.fn - a function that returns a promise that we want to keep checking till desire value is reached
 */
function waiter(fn, config){
    config = config || {};
    var deffered = Driver.promise.defer(),  
        wt = config.waitTime || 100,
        mwt = config.maxWaitTime || 3000,
        timeoutReached = false,
        pCall = function(){
                        fn().then(pThen, pCatch);
                    },
        pThen = function(data){
                    if(timeoutReached)  return;
                    if(config.expectValue){
                        if(config.opposite){                        
                            if(data == config.expectedValue){
                                setTimeout(pCall, wt);
                            }else{
                                clearTimeout(vTimeout);
                                deffered.fulfill(true);
                            }
                        }else{
                            if(data == config.expectedValue){
                                clearTimeout(vTimeout);
                                deffered.fulfill(true);
                            }else{
                                setTimeout(pCall, wt);
                            }
                        }
                    }else{
                        deffered.fulfill(true);
                    }
                },  
        pCatch = function(err){
                    if(timeoutReached)  return;
                    if(config.opposite){
                        deffered.fulfill(true);
                    }else{
                        setTimeout(pCall, wt);
                    }
                };  

    pCall();    

    var vTimeout = setTimeout(function(){
        timeoutReached = true;
        if(config.opposite){
            deffered.fulfill(true);         
        }else{
            deffered.reject(new Error('timed-out'));
        }
    }, mwt);
    return deffered.promise;
}

示例用法（针对您的情况）：

var myPromise = function(){
    return driver.findElement(webdriver.By.xpath(...)).click();
};

//default use
waiter(myPromise).then(function(){
    console.log('finally...');
}).catch(fucntion(err){
    console.log('not working: ', err);
});

// with custom timeout after 10 seconds
waiter(myPromise, {maxWaitTime: 10000}).then(function(){
    console.log('finally...');
}).catch(fucntion(err){
    console.log('not working: ', err);
});

Answer 2

您对auto lo iface lo inet loopback auto eth0 iface eth0 inet static address 192.168.0.101 netmask 255.255.255.0 network 192.168.0.0 broadcast 192.168.0.255 gateway 192.168.0.1有正确的想法，但没有正确编码。这是有用的东西：

getStaleElement

以下是演示其用法的代码。您会发现function retryOnStale(selector, callback) { return browser.findElement(selector).then(callback) .thenCatch(function (err) { if (err.name === 'StaleElementReferenceError') return retryOnStale(selector, callback); throw err; }); }包含的代码会导致陈旧的元素异常发生，并且它具有retryOnStaleIllustrate用于诊断。然后是console.log，它与我上面显示的相同。

retryOnStale

此示例可以执行并应生成此输出：

var webdriver = require('selenium-webdriver');
var chrome = require('selenium-webdriver/chrome');
var By = webdriver.By;
var until = webdriver.until;

var browser = new chrome.Driver();

browser.get("http://www.example.com");

function make_stale() {
    browser.executeScript("document.body.innerHTML = " +
                          "'<p id=\\'foo\\'>foo text</p>'");
}

// Create our initial p element with id `foo`.
make_stale();

var fake_stale = 10;

// We have to use var ... = ... because later in this code we are
// going to change the value of retryOnStaleIllustrate.
function retryOnStaleIllustrate(selector, callback) {
    return browser.findElement(selector).then(function (element) {

        //
        // This code is here to simulate a process that causes the element
        // we acquired to become stale.
        //
        if (fake_stale) {
            make_stale();
            fake_stale--;
        }

        return callback(element);
    }).thenCatch(function (err) {
        if (err.name === 'StaleElementReferenceError') {
            console.log("stale: retrying");
            return retryOnStaleIllustrate(selector, callback);
        }

        throw err;
    });
}

retryOnStaleIllustrate(By.id("foo"), function (element) {
    element.getText().then(console.log);
});

// Once we remove the code to simulate an element becoming stale, and
// the console.log for diagnosis, this is what we are left with:
function retryOnStale(selector, callback) {
    return browser.findElement(selector).then(callback)
        .thenCatch(function (err) {
            if (err.name === 'StaleElementReferenceError')
                return retryOnStale(selector, callback);

            throw err;
        });
}

// This just shows that retryOnStale returns a promise which can be used.
retryOnStale(By.id("foo"), function (element) {
    return element.getText();
}).then(function (text) {
    console.log(text);
});

browser.quit();

所有stale: retrying stale: retrying stale: retrying stale: retrying stale: retrying stale: retrying stale: retrying stale: retrying stale: retrying stale: retrying foo text foo text行和第一个stale: retrying都是由使用foo text的代码生成的。最后一个retryOnStaleIllustrate行由使用foo text的代码生成。

Selenium WebDriverJS thenCatch没有捕获StaleElementException

2 个答案: