thing we have planned to make part of the Add-on SDK story is to have
"automatic repacks" for developers using the SDK. What this means is
that if you host
your add-on, built with the SDK, on AMO (addons.mozilla.org), we would
automatically rebuild it everytime we release a new version of the
Add-on SDK to maintain compatibility with a new version of Firefox. This would make sure that your add-on was always up-to-date with the latest version of Firefox.
is still the plan, but for our first attempt we noticed some things
that were wrong with the plan as we currently have it and would like to
propose a way of getting past these problems and getting to a new repack
What Went Wrong
first problem we faced is that the repacker is the first service to use
AMO's brand-new APIs for updating add-ons, and we hadn't tested the
interaction between the two sites sufficiently beforehand, so we had to
implement fixes for issues we encountered during the repack testing,
which slowed down the testing.
our testing was short and not deep enough for what we were trying to
accomplish. The repack team didn't get enough testing in themselves, nor
did they make it possible for other project participants to test
repacks and suggests issues and fixes before the production run of
Finally, what we are fundamentally trying to do is repackage a derived format without the source code it came from as reference, like decompiling a program, making changes, and then recompiling it. This is something that is hard to do and as it turned out, didn't work very well. We could fix that by including the source code in the XPI. However,
including the source code in the XPI would defeat our goal of making
the XPI size as small as possible (this is extremely important for
mobile versions of Firefox).
So what can we do about these issues? First of all, the repack team will answer the testing problems by
starting testing earlier and sharing the results with everyone. In
addition, the use of the AMO APIs is now solved as the calls we are
using are now verified and tested.
However, the issue about the required sources for a clean rebuild is a bit more difficult and needs a new proposal.
In the short-term I propose that we only repack add-ons which are built using the Add-on Builder.
This is the quickest and safest solution as we have access to all the
sources with Builder-based add-ons. The repack process is much simpler
too as we don't have to unpack a XPI first. For those who use a local installation of the Add-on SDK to build an add-on, we will document how to repack your add-on and the process for pushing the new one to AMO. In addition, you can move your add-on to the Add-on Builder
and take advantage of the automatic repacks if you'd like, but do keep
in mind that the Add-on Builder is still in beta at this point.
long-term solutions will need to be studied and debated a bit more. One
option we have is to create a "source package" that can be pushed to
AMO for use in repacking. However, this would mean that AMO would have
to store these source packages and generate XPIs from them in addition to taking on
responsibility for repacking when a new SDK is released. Obviously this
would involve adding a great deal of functionality to AMO, as well as
tooling up the services side to store these new, larger packages.
Another option is to land parts of the Add-on SDK into Firefox itself, including API implementations and the module loader. If an API already in Firefox needs updating to maintain compatibility with changes to Firefox, we won't need to repack add-ons that use that API, as the updates can be made to that new version of the browser rather than each individual add-on.
Doing this has other benefits as well. For example, it may help reduce
XPI sizes tremendously. However, this too would take a bit of time to
implement and is thus a long-term solution.
At this point we think that the short-term solution of just repacking Add-on Builder-based add-ons would be the best approach. We would also provide documentation
describing the simplest approach for repacking add-ons along with best
practices and troubleshooting. In addition, we would look into how best to notify authors when their add-ons need to be repacked manually.
Still, we also want to know what you think about this as well as the long-term ideas. Please feel free to leave your comments or suggestions about this proposal.