I am writing a Google Chrome extension. One of my content scripts has a little bug that I can't find and the Google Chrome debugger appears to be useless for this purpose. The code stops on an Uncaught typeError: Cannot set property 'value' of null. I can see this by opening the debugger and viewing the console after the code fails. But my content script does not appear in the list of scripts shown in the debugger at this point. There are a lot of scripts shown there, including a big block of scripts in light blue. But none named "profile.js" which is my content script.
I tried "location.reload(); but it simply returns "undefined." I'd love to step thru this code and find the problem but I can't figure out how to do it. I've set alerts to try to track the problem but once I click on the alert, the script continues with no opportunity to invoke the debugger. Based on the result of the alert experiment, it appears the code is failing at the very end. I presume the code is finished by the time the error is caught and the script is no longer available to the debugger.
I tried adding this line to the script: "debugger;" to try and force the debugger to open but there is no change whatever to the execution of the code. It fails as usual and as usual I can open the debugger, find the console message and the big list of scripts that does not include mine.
How can I pause execution of the code using a line in the code itself? I just want to stop execution of the code at the beginning, invoke the debugger, set up some breakpoints, resume execution and monitor some variables. That seems like a pretty simple and do-able request.
Any ideas?
Related
I cannot figure out how to debug my simple extension. Script (a content script) loads (because the first console.log call shows in the tab's console) but then nothing. There's no error what so ever and no second console.log call.
My question is not about solving my code issue (there surely is one, if only firefox would tell me where), it's about finding the place where warnings/errors about the add-on are in firefox (like 'sdfsdf has no object property ...')
about:debugging is no help, the console it can open shows some errors (example: 'Error: Service "domainInfo" is not available. Make sure it appears in the "requiresServices" property of the module's background where is it used.') that have nothing to do with what I'm trying to do (I can tell from the source and nature of errors)
// start of file
console.log('I AM LOADING');
// simple DOM manipulation code here...
console.log('I AM LOADED');
// end of file
The content scripts are supposed to be debugged with the DevTools instance attached to the web page.
However, as you noticed, the errors in the content script are not reported in the tab's Web Console due to a bug. (As of Firefox 70.)
As a workaround you can:
use try..catch with logging,
check the Browser Console (which does show error in the content script)
use the Debugger's "pause on exceptions" option.
Long story short, I am debugging a big application which I didn't write. It is throwing an error when it runs on the server on which it is supposed to be run, so I am testing on my own machine with the debugger attached to see what happens.
It has thousands of lines of code, and has been running for a couple of hours now. I want to know which line of code is currently executing, so I can get a rough idea of how long is left, but I don't want to Break All as the code is...rickety.
Short of firing watchpoints all over the place in a spray and pray fashion, is there a non-invasive way to see which line of code is executing right now?
Thanks
Process Explorer can show the currently executing line and call stack in the process.
Right-click a process, click Properties, and then click the Threads tab.
I'm currently (trying) to develop an app with Worklight Studio 5.0.6 and Dojo (Mobile) 1.8.3. I have a really hard time to to find a proper method for debugging. After waiting 5-10 minutes for the build an deploy-process on the server, an error usually looks like this in the Chrome debugger:
How am I supposed to track down this error in MY source? The whole stack trace consists entirely of Dojo code which generates an absolutely useless error message after 20 abstraction layers.
Seriously, how do you guys handle this in real life? What methods do you use for debugging Dojo-driven apps in the browser?
spyro
For dojo.parse errors, I find it useful to pause the Chrome debugger on all exceptions (the purple icon on your screenshot, should be blue). You usally get more details about the cause of the error, the name of the DOM node being parsed, etc. in the first exception being raised.
Rémi.
Debugging dojo based application should be the same as debugging any javascript application.
Usually I will follow these steps:
add console.log() somewhere in code: this is fast and most of time this is enough.
set breakpoint in debugger: if step 1 is not enough, you can base on error information to set breakpoint before error line, then step in or step out.
comment out recently changes: for some error which is hard to find the error line, for example, parse error in your case, the good way is comment out your recently changes one by one till back to your last working version. Or, return to your last working version, then add code back one by one.
Create a simple application to reproduce the error : if your application is very complicate and it is hard for you to follow above methods, you can try to create a new application which mimics your current application but with simple logics and try to reproduce the error.
Based on experience : Some errors, for example, extra ',' in the end of array which works at chrome and firefox, will report a nonsense error information at IE. Debug these kinds of errors is very difficult, you can base on your experience or do a google search.
Did you provide isDebug: true in your dojoConfig? Also, try to see if the same occurs in other browsers.
Update: I recently discovered that there are issues with Google Chrome and Dojo debugging and I think it has to do with the asynchronous loading of files. As you can see in the provided screenshot of #spyro, the ReferenceError object is blank (which you can notice because of the empty brackets {}). If you want to solve that, reopen the console of Google Chrome, (for example by tapping F12 twice). After reopening the ReferenceError should not be empty anymore and now you can expand that object by using the arrow next to it and get a more detailed message about what failed.
Usually what I do in situations like that is to place a breakpoint inside the error callback (line 3398 in your case) and then look into the error variable ("e").
I am not sure how familiar you are with the Web Inspector, but once you hit the breakpoint open the Web Inspector 'console' and check for the error properties "e.message" and "e.stack" (just type in "e.message " in the console).
Also, during development it is better to avoid Dojo optimization / minification, which greatly improve your debug-ability.
Bottom line is to try to place the breakpoint before the error is thrown.
Where XCode generate error for application crash ?
I'm crazyng ! My application when open second file xib with webview then it crash. But I don't know why ? how can i Know where is error ?
You need to learn how to use the debugger in Xcode.
Run your app under the debugger then instead if simply getting a stack trace Xcode will stop at the line the fault occurs and show you your code and variables. You can then examine the contents of your variables, the call tree, etc. and hunt down the problem.
Once you know the general area of the problem you can place breakpoints to pause your application before the problem occurs and check whether your variables have the values expected etc. Then you can run till the next breakpoint, or step through your code a line at a time.
You can add code, such as NSAssert's and NSLog's to your app to check progress and display information without stopping the run, etc.
It's a process, and some problems will be harder to track down, but you'll get quicker at it with practice.
The Xcode documentation will tell you all about the debugger.
HTH
Is there a way to invoke the script debugger programmatically?
I want to create a dialog box that offers an option to start the debugger (as if it had reached a breakpoint in one of the callers), similar to the one that QTP offers when it encounters a playback error.
This is for QTP, but i estimate that if one can do this for VBS, it'll work there too.
Updated update
The stop statement does what I want -- except for this (in conjunction with QTP/UFT):
it stops where the stop statement is (and not in the caller's code) (I think I could work around that by putting the function with the stop statement into a file that I load in a way that it won't be jumped into by the debugger (LoadLibrary? ExecuteFile?));
it requires me to have triggered one "real" breakpoint during the run session previously, and continued execution with "Run"/F5.
Does Err.Raise work for what you're trying to achieve?