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# Firefox Snap Packaging
This page explains interactions between Firefox and Snap packaging format.
## Where is the upstream
The code reference itself is mozilla-central, but the packaging is being worked
This packaging includes a few more bits and dependencies, including compiler.
It will also re-download the mercurial repository: this is on purpose.
## Where to report bugs
All bugs should be reported to Bugzilla's `Third Party Packaging` component,
and marked as blocking `snap` meta-bug.
## Full build process
There may be a few differences between a simple repack and a real full build of
the Snap, you can find mention of the repackage usage below.
The following steps should be enough, assuming you have properly setup:
While the documentation still refers to `Multipass`, the Firefox Snap and its
dependency had some requirements that made it better suited to use `LXD`.
When performing the checkout, please keep in mind the branch mapping:
- `edge` is our `nightly`
- `beta` is our `beta`
- `stable` is our `release`
- `esr` is our `esr`
```shell
snap run snapcraft
```
You should end up after some time with two files: `firefox-XXX.snap` and
`firefox-XXX.debug`. The first one is the package you will want to `snap
install` while the second one holds your debugging symbols.
You can then install the package:
```shell
sudo snap install --name firefox --dangerous ./path/to/firefox-XXX.snap
```
If you want to have parallel installs, then you can change the `--name firefox`
to something else. This will be the name you use for `snap run
installed-name`, e.g., `--name firefox_nightly` will require you to run
`snap run firefox_nightly`.
`Snap` has a notion of plugs and slots, and some gets automatically connected
in various ways, including depending on the `Snap Sore` itself, and if you
manually install as `firefox` it should reuse them (but you might do bad
things with your profile). If you install using another name, then the `Snap
Store` automatic connection will not happen and this can result in a broken
state. Inspecting `snap connections firefox` using a store-installed snap
should get your an accurate list that you can replicate.
## Cross-compilation
There is now support for cross-compilation for `arm64`.
To produce cross-compiled version locally:
- follow the steps above for building, except you need to pass
`--build-for=ARCH` to `snapcraft`
- this needs `snapcraft` of at least v8.x
- make sure you uncomment the `##CROSS-COMPILATION##` lines due to Launchpad
limitations
Builds on Treeherder as well as Try pushes are also available using
cross-compilation. Tests on Treeherder will also be supported when ARM-based
workers will be available, confere [Bug 1855463](https://bugzilla.mozilla.org/show_bug.cgi?id=1855463).
## What CI coverage
Currently, there are upstream-like builds on treeherder. They are scheduled as
a cron task daily and includes:
- building opt/debug versions of the snap
- building them on all branches
- running a few selenium-based tests
The build definitions {searchfox}`are based on docker <mozilla-central/rev/3c72de9280ec57dc55c24886c6334d9e340500e8:taskcluster/docker/snap-coreXX-build/Dockerfile>`.
It should be noted that for the moment, all tasks needs to run under docker.
However, this setup is not working for `Snap` since it interacts with `SystemD`
which does not work under `Docker`. This is why the installation is handled by
{searchfox}`the install-snap script <mozilla-central/rev/3c72de9280ec57dc55c24886c6334d9e340500e8:taskcluster/docker/snap-coreXX-build/install-snap.sh>`
rather than plain `sudo snap install`, and also why we need to run `snap` in
`destructive mode` (which is fine since we are within a docker container). This
does not apply to the tests case which relies on newly-available wayland
virtual machines.
Outside the build oddities because of the setup, it should be noted that those
builds are as close as possible to upstream. This means:
- the mozilla-central hash they run against is not matching the source code it
builds from, and one should inspect the build log to see the mercurial clone
step
- it builds using the clang build within the snap definition
The tests are defined {searchfox}`within the docker subdirectory <mozilla-central/rev/3c72de9280ec57dc55c24886c6334d9e340500e8:taskcluster/docker/snap-coreXX-build/snap-tests/tests.sh>`.
They are using Selenium because this is what was used by pre-existing tests ran
on GitHub Actions from upstream.
Their coverage is ensuring that we get a basic working browser out of builds.
It includes some tests that previously were manually ran by QA.
## How to hack on try
Build and test tasks can be explored via `mach try fuzzy --full` by searching
for `'snap 'upstream`. There is a bit of hacking for try to make sure we
actually don't re-download the mercurial repo and directly reuse the clone
generated by `run-task`, handled in the {searchfox}`run.sh script <mozilla-central/rev/3c72de9280ec57dc55c24886c6334d9e340500e8:taskcluster/docker/snap-coreXX-build/run.sh#61-72>`.
So pushing to try is basically just:
```shell
mach try fuzzy --full -q "'snap 'upstream 'local"
```
Because of the build process, a full opt build will take around 1h45-2h while a
debug build will be around 60 minutes, the difference coming from the use of
PGO on opt builds.
If you need to reuse a package from the Snap Store or from the latest
mozilla-central or a specific successful build, you can use `USE_SNAP_FROM_STORE_OR_MC` en
variable ; setting it to `store` will download from the Snap Store (warning:
no debug builds on the Snap Store, so whatever `debug` variants we have will
be an `opt` build in fact), and setting to a TaskCluster index value will
download from the index. Set it to `latest` if you want latest, or explore
the TaskCluster index for others. Any `try` will be pulled from latest
`nightly` while others will be fetched from their respective branches.
## How to hack locally
After a successful build, you can also build a Snap by performing a repackaging
using the `mach repackage snap` tool. This requires a `snapcraft` working
installation relying on `LXD`, which installation steps are