Developing Firefox Addon for multiple SDK version

Question

I see each cfx tools always produce xpi with its own minVersion and maxVersion. However, those are limited to the versions which the SDK is compatible with, e.g. SDK 1.14 only for FF 21 - 25.0a1 , SDK 1.17 only for FF 26 - 30. My questions are:

1. Do I need to package my extension with new SDK everytime new version comes out ?
2. How do I maintain and update my extension in the future? Does Addon Developer Hub provides a way to submit the same extension for multiple SDK versions ? I tried to look around but couldn't find a way to submit multiple versions. I want to make FF 21 as the minimum version, since that's the version which has SDK built-in. My extension currently compiles with both SDK 1.14 and SDK 1.17 with only cosmetic(syntax) adjustment.

Answer 1

The developer hub lets you choose which versions of Firefox the add-on is compatible with. This is just a GUI for setting the minVersion and maxVersion in the install.rdf. As long as you don't use modules or methods that require Firefox 22+, it shouldn't matter which version of the SDK you use, as the version of the SDK being run is determined by the version on your user's browser.

It's hard to find module specific compatibility (you can always go to the docs for the specific module and look at the edit history), but have a look at the SDK API Lifecycle to understand which modules can be used. Some notable example are:

• The new UI modules require FF29 and some of their features require FF30.
• The widget module is deprecated from FF 29 onwards, being replaced by the above.

One way to handle the above for backward compatibility is to do the following:

const { version } = require('sdk/system/xul-app');
if (version < 29) var widget = require("sdk/widget").Widget({...});
else var button = require("sdk/ui/button/action")({...});

So, to be clear:

1. It doesn't matter which version of the SDK you use unless you want to use new modules.
2. No, you shouldn't make multiple versions of your add-on. If you want to use new modules for new browsers, follow the code example above.

Answer 2

It's true that you must use valid existing application versions but you generally don't need to repackage your addons, unless of course a change in the SDK directly affects your addons.

The reason for this is that by default the max target version is not going to be checked.

From the install manifest documentation:

strictCompatibility

A Boolean value indicating if the add-on should be enabled when the version of the application is greater than its max version. By default, the value of this property is false meaning that the compatibility checking will not be performed against the max version.

<em:strictCompatibility>true</em:strictCompatibility>

Usually, there is no need to restrict the compatibility: not all new releases will break your extension and, if it is hosted on AMO, you'll get notice several weeks in advance if a potential risk has been detected. Moreover, an extension being disabled, even for a short period, leads to a bad experience for the user. About the only time you should need to set this if your add-on does things that are likely to be broken by Firefox updates. You do not need to set this flag if your add-on has a binary component, since add-ons with binary components are always subject to strict compatibility checking (because binary components need to be rebuilt for every major application release anyway).

There is also is a recommendation for choosing version ranges.

minVersion and maxVersion should specify the range of versions of the application you have tested with. In particular you should never specify a maxVersion that is larger than the currently available version of the application since you do not know what API and UI changes are just around the corner. With compatibility updating it is not necessary to release a whole new version of the extension just to increase its maxVersion.

Technically you can use wildcards, but the documentation mentions several times that AMO verifies and possibly rejects addons with incorrect versions.