Implement abort-on-property-read snippet

[hfiguiere]

Background

Some circumvention scripts depend on global properties on the window object. The execution of such scripts can be aborted by throwing an error when the property is read.

There is a technique in uBlock Origin called ​abort-on-property-read that does this.

What to change

Implement a snippet called abort-on-property-read that wraps a given property of the window object and throws an error if the property is read.

Hints for testers

Try this:

<!-- test.html -->
<div>
  Lorem ipsum dolor sit amet, consectetur
  adipiscing elit, sed do eiusmod tempor
  incididunt ut labore et dolore magna aliqua.
</div>
<script src="script.js"></script>

/* script.js */
adsShown = false;

setTimeout(() =>
{  
  if (!adsShown)
  {
    let ad = document.createElement("div");
    ad.id = Math.random().toString(36).substring(2);
    ad.innerHTML = "<div><span>Check this!</span><span class='label'>Ad</span></div>";
    document.body.appendChild(ad);

    adsShown = true;
  }
},
500);

When you load this page, it should show the "Check this!" ad. If you then add the filter localhost#$#abort-on-property-read adsShown and reload the page, the ad should no longer be shown. Also there should be no error in the tab's console.

[mjethani]

chefkoch.de,pcwelt.de,vox.de,cinema.de#$#abort-on-property-read trckd
chefkoch.de,pcwelt.de,vox.de,cinema.de#$#abort-on-property-read uabpd3

This can also be just one filter, like so:

chefkoch.de,pcwelt.de,vox.de,cinema.de#$#abort-on-property-read trckd; abort-on-property-read uabpd3

[abpbot]

A commit referencing this issue has landed:
​Issue 6969 - Implement abort-on-property-read snippet

[abpbot]

A commit referencing this issue has landed:
​Issue 6969 - Implement abort-on-property-read snippet

[mjethani]

Hubert, I think the hints for testers should have a standalone test case just like all the other snippets (see #6919 for example).

[mjethani]

I am reopening this until there's a standalone test case.

[hfiguiere]

We should make a new test page with this.

[Ross]

Thanks for the test HTML. I agree all of these examples should be added to the proper test pages. I've added this one to the list of test data to create to the Test Data section of the ABP WebEx Testing notes document.

[Ross]

Done. This works with the example provided with no errors and as far as I can tell, seems to be working fine removing the ads on the domains listed above in comment 8.

ABP 3.4.0.2189
Firefox 63 / 51 / Windows 8
Chrome 70 / 49 / Windows 8
Opera 36 / 56 / Windows 8

[SMed79]

Question: Does SNIPPET options have an exception syntax rule?

Background: Debug an issue without disabling the main list (ABP filters).

example.com#@#abort-on-property-x xyz done not seems to work (tested for ​#114, ​#99 & ​#112)

[mjethani]

@SMed79 not yet, but the plan is to apply such exceptions to snippet filters as well (#6842). We will do it soon.