stage package cache no longer working

[Kyle Fazzari]

Snapcraft currently caches stage-packages. For example:

$ snapcraft pull
Preparing to pull ros-base
Pulling ros-base
Preparing to fetch compilers...
Fetching compilers...
Get:1 http://packages.ros.org/ros/ubuntu xenial InRelease [4025 B]
Get:2 http://security.ubuntu.com/ubuntu xenial-security InRelease [102 kB]
Hit http://archive.ubuntu.com/ubuntu xenial InRelease
Ign http://packages.ros.org/ros/ubuntu xenial InRelease
Get:3 http://archive.ubuntu.com/ubuntu xenial-updates InRelease [102 kB]
Get:4 http://archive.ubuntu.com/ubuntu xenial-security InRelease [102 kB]
Get:5 http://archive.ubuntu.com/ubuntu xenial-updates/main amd64 Packages [463 kB]
Get:6 http://archive.ubuntu.com/ubuntu xenial-updates/universe amd64 Packages [387 kB]
Get:7 http://archive.ubuntu.com/ubuntu xenial-updates/universe Translation-en [144 kB]
Fetched 1,305 kB in 0s (0 B/s)
Get:1 http://archive.ubuntu.com/ubuntu xenial/main amd64 libgmp10 amd64 2:6.1.0+dfsg-2 [240 kB]
Get:2 http://archive.ubuntu.com/ubuntu xenial/main amd64 libmpfr4 amd64 3.1.4-1 [191 kB]
Get:3 http://archive.ubuntu.com/ubuntu xenial/main amd64 libmpc3 amd64 1.0.3-1 [39.7 kB]
<snip>

Now check `~/.cache/snapcraft/apt/` and you'll see that snapcraft has cached all those debs. However, that cache doesn't seem to be used, as shown by this:

$ snapcraft clean && snapcraft pull
Cleaning up priming area
Cleaning up staging area
Cleaning up parts directory
Preparing to pull ros-base
Pulling ros-base
Preparing to fetch compilers...
Fetching compilers...
Get:1 http://packages.ros.org/ros/ubuntu xenial InRelease [4025 B]
Ign http://packages.ros.org/ros/ubuntu xenial InRelease
Hit http://security.ubuntu.com/ubuntu xenial-security InRelease
Hit http://archive.ubuntu.com/ubuntu xenial InRelease
Hit http://archive.ubuntu.com/ubuntu xenial-updates InRelease
Hit http://archive.ubuntu.com/ubuntu xenial-security InRelease
Fetched 4,025 B in 0s (0 B/s)
Get:1 http://archive.ubuntu.com/ubuntu xenial/main amd64 libgmp10 amd64 2:6.1.0+dfsg-2 [240 kB]
Get:2 http://archive.ubuntu.com/ubuntu xenial/main amd64 libmpfr4 amd64 3.1.4-1 [191 kB]
Get:3 http://archive.ubuntu.com/ubuntu xenial/main amd64 libmpc3 amd64 1.0.3-1 [39.7 kB]
<snip>

See that the packages are being downloaded again instead of being unpacked from the cache.

[Kyle Fazzari (kyrofa)]

Fix here: https://github.com/snapcore/snapcraft/pull/1113

[Kyle Fazzari (kyrofa)]

Better fix here: https://github.com/snapcore/snapcraft/pull/1122