snapcraft remote-build snapcraft.yaml validation too strict

[Frode Nordahl]

When attempting to use `snapcraft remote-build` I get this error:

$ snapcraft remote-build --build-on arm64
snapcraft remote-build is experimental and is subject to change - use with caution.
Issues while validating snapcraft.yaml: The 'environment/LD_LIBRARY_PATH' property does not match the required schema: '' is not of type 'number' or '' is too short

Using an empty LD_LIBRARY_PATH is an requirement for some classic snaps [0][1] and building the snap locally or indeed through the Launchpad snap package infrastructure causes no issue.

Why does the `snapcraft remote-build` command impose this restriction, and can it be lifted?

0: https://github.com/juju/charm-tools/blob/977ec1ff795f5a8692f8061fc16aa01adf9478cf/snap/snapcraft.yaml#L14-L23
1: https://github.com/openstack-charmers/octavia-diskimage-retrofit/blob/6de2a47491df9e983b458bc7d24f0e035c55c9c3/snap/snapcraft.yaml#L32-L44

[Callahan Kovacs (mr-cal)]

Thanks for the report!

I'm able to reproduce this. This has the same root cause as https://bugs.launchpad.net/snapcraft/+bug/2007789.

The issue arises because core22 snaps use the core18|20 implementation of `remote-build`. The core18|20 implementation raises this error when parsing core22 architecture syntax.

(tracking internally with CRAFT-1640)