Bug Description

As per one users comments in the WordPress support forums AdSense policy dictates that ads should not be displayed on 404 URLs.

Consider adding a conditional statement to ensure ads don't appear on such URLs.

More insights on AdSense policy available here, with the below guidance included:
Publishers are not permitted to place ads on any non-content based pages like thank you, error, log in, or exit pages.

Do not alter or remove anything below. The following sections will be managed by moderators only.

Acceptance criteria

• The AdSense snippet should not be included on any WordPress 404 URLs (is_404()), neither for AMP nor for non-AMP.
• This should be unconditional and always take effect, there should be no setting for it.

Implementation Brief

• Update the Modules\AdSense\Tag_Guard::can_activate method to return FALSE if is_404() returns TRUE.

Test Coverage

• Update the Tests\Modules\AdSense\Tag_GuardTest class to make sure that Tag_Guard::can_activate method returns correct result for 404 pages.

Visual Regression Changes

• N/A

QA Brief

• Activate and connect AdSense module with use snippet setting enabled;
• Go to the homepage or any page on the frontend and make sure that ad code is added to the page;
• Go to a non-existing page (it should result in 404 status) and make sure that ad code is not added.

Changelog entry

• Ensure that the AdSense snippet is not included on 404 pages in the frontend.