Handle content blocking in WebEngine

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➤ Matthew Reagan commented:

I’ve added some early hooks related to this, but am planning to revisit this later in the WebEngine refactor per discussions with Laurie Marceau. This area is particularly complicated for a couple reasons:

• We have scripts that generate the blocking lists (the JSON files consumed by WebKit) and a lot of WebKit-specific code in the client currently. If we want to have WebEngine acting as an abstraction layer then it means much of this will (probably) need to move out of the client and into WebEngine. This will be a pretty significant undertaking and will potentially involve changes to our CI also since it might affect how and when we run the related scripts
• The content blocking code itself is somewhat complicated and we also need to take things like the safelist/whitelist into consideration, and the fact that Focus and Firefox may have different requirements for how we handle strict vs standard tracking protection
• There are still some unknowns around how exactly this API should work in practice

Going to move this ticket back to Open for now and pick this up later once we are a bit further along. (cc Orla Mitchell)

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➤ Laurie Marceau commented:

Shavar deprecation project

I should also mention that the Shavar project is deprecated and we didn’t have any content blocking files update for a while. The epic tracking this is https://mozilla-hub.atlassian.net/browse/FXIOS-7217 ( https://mozilla-hub.atlassian.net/browse/FXIOS-7217|smart-link )

There’s a channel called #content-blocking-for-firefox-ios that aims to track this work with key people, but that project hasn’t been picked up yet. We can continue with the current script (triggered by bootstrap.sh) to fetch the Shavar files for now, until this project is kicked off.

Focus VS Firefox

Focus and Firefox have some differences when it comes to how the files are fetched since the script was updated for Firefox but not Focus. If we create a package under BrowserKit for the content blocker generator ( https://github.com/mozilla-mobile/firefox-ios/tree/main/firefox-ios/Client/ContentBlocker/ContentBlockerGenerator )then Focus could use the same. There’s slight differences between Firefox and Focus on how content blocking files are applied depening on the standard or strict mode, but passing options to the WebEngine, this could be adapted to each Client (or maybe we can discuss with product to align Content blocking between the two products).