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Debugger error

Hi and thanks for a great software

I'm a web developer and usually work with chrome debugger tools and 'Pause on exceptions' enabled.

Very often when working on a page I get an exception in main_content.js line 53:

    appAPI.message.addListener( { channel: "popup" }, function( info ){

Uncaught TypeError: Cannot read property 'message' of undefined

(seems like appAPI is not defined)

which I presume has to do with clibu web clipper.


Hi Mika,

Thanks for your kind words and bug report. I have Chrome dev tools open all the time as well, however I don't have  'Pause on exceptions' enabled and have now enabled it.

I tried various activities using the Web Clipper and so far haven't seen any exceptions.

Can you provide any more details on what you are doing when the exception occurs. I assume you are using the Web Clipper in some way?

Also is Clibu open in the Browser?

FYI appAPI is a window global variable which is common between the Extension and the Content script. You can actually access and debug the content script in the Chrome Debugger via. Sources | Content Scripts. It is under the file:// item. The file is app_api_2016.js 

This screenshot shows it. Could you check this next time the exception is raised - thanks.


Hi Neville,

I have clipbu open in a desktop shortcut (created in chrome settings -> more tools -> add to desktop)

I get the exception intermittently while working inside my browser on a completely unrelated tab.

under sources -> content scripts -> file://

I have one folder including one file: main_content.js where the exception is as I wrote above

Global -> appAPI is not there (it is not defined), this is why the exception is raised.

Thanks !

Hi Mika,

Thanks for checking this out for me.

Is the unrelated Tab some random web page?

Are you doing any Browser development of your own when the exception is raised?

I assume you are using the latest version of Chrome.

yes. This is why it's annoying, as I suddenly get an exception on the clibu code while debugging a page that has nothing to do with it.

It only happens directly after refreshing a page I'm developing and only intermittently.

yes, latest chrome.

So it only happens when you are debugging your own code, right?

Is this code a Browser Extension or normal JS code in the Web page?

Has your code raised an error of some sort when the Clibu code crashes?

I'm wondering if your code is somehow trashing Clibu's code, although this shouldn't be possible. That said maybe Chrome somehow behaves differently when the Debugger is running.

FYI The Clibu code that is raising the exception is running in the context of the current web page, however it is (supposed to be) running in a isolated sandboxed environment. 

It is injected into the web page when the page loads and executed immediately. So this is the only time that the exception should occur.


Yes it happens when debugging my own page (not an extension).

I just refresh the page and get the exception, if I press F8 (resume) my page continues fine. I can't see how it can be a problem with my code as it happens intermittently. 

So not sure what's going on ... perhaps you can add an exception handler there ?


Ok, I'll add an exception handler on the next release of the Web Clipper. 

In the meantime you could disable the Web Clipper Extension whilst you are debugging.

FYI I'm not seeing the issue here and have Dev Tools and the Debugger open all the time. And I'm doing lots of debugging at the moment. This is Clibu debugging, but that shouldn't make any difference.

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