Add-on Compatibility for Firefox 45

Firefox 45 will be released on March 8th. Here’s the list of changes that went into this version that can affect add-on compatibility. There is more information available in Firefox 45 for Developers, so you should also give it a look.

General

• JavaScript expression closures (shorthand function syntax) are deprecated. From the bug report, this is an example of the deprecated syntax: var x = function() 1;
• Disallow calling WebIDL constructors as functions for system callers. Constructors should always be called using the new keyword.
• Drop support for jar: URIs by default. This only affects web content being loaded with the jar: protocol.

UI

• Remove Panorama / Tab Groups. There are a couple of add-ons that are already taking the lead and bringing back the feature for those who need it.
• Replace globe with the “i” icon, keep separate lock for secure pages. This changes the appearance and behavior of the identity information that appears to the left of the current URL.
• Stop using icon sprites for command buttons. This would only affects extensions and themes that touch the buttons in the developer tools.

XPCOM

• Use the loading document’s principal to populate loadInfo for Favicons. Comment 51 sums it up well. If you call mozIAsyncFavicons.setAndFetchFaviconForPage or mozIAsyncFavicons.replaceFaviconDataFromDataURL, you should pass the right principal using the new optional argument.
• Replace removeAllPages with history.clear() and deprecate it.
• Remove nsIURIChecker.
• Remove nsISaveAsCharset. The interface is still there and should work, but some of the parameters its methods take are being ignored now.
• Make listbox.selectedItems be an nsIDOMNodeList.

Signing

• Firefox is currently enforcing add-on signing, with a preference to override it. Firefox 46 will remove the preference entirely , which means your add-on will need to be signed in order to run in release versions of Firefox. You can read about your options here.

New

• Support a simplified JSON add-on update protocol. Firefox now supports a JSON update file for add-ons that manage their own automatic updates, as an alternative to the existing XML format. For new add-ons, we suggest using the JSON format. You shouldn’t immediately switch for older add-ons until most of your users are on 45 and later.

Let me know in the comments if there’s anything missing or incorrect on these lists. If your add-on breaks on Firefox 45, I’d like to know.

The automatic compatibility validation and upgrade for add-ons on AMO will happen in the coming weeks, so keep an eye on your email if you have an add-on listed on our site with its compatibility set to Firefox 44.