404 error detection broken on Safari in Manifest v3

[cgorringe]

Describe the bug

In the latest v3.4.2 code which upgraded to Manifest v3, the extension will not work in Safari without removing the webRequest permission and commenting out the chrome.webRequest functions. Unfortunately, the result of doing so removes the ability for the extension to detect 4xx error codes such as 404 Not Found. When this feature is turned on in Settings, the red dot and/or popup will no longer appear on a 404 page.

Environment (please complete the following information):

• Webextension version: v3.4.2 (modified)
• Browser + version: Safari 18.0
• OS + version: macOS Sonoma 14.7

[cgorringe]

Testing this on branch safari-manifest-v3

[cgorringe]

I think this is a bug in Safari. It should support webRequest functions. I don't know why it doesn't in Manifest v3. It appears we need this to detect any kind of http error code.

[cgorringe]

Filed a compatibility report on MDM here: mdn/browser-compat-data#24571