Shellcheck resolves source directive relative to the working directory that it was executed, no relative to the file, e.g.
src/
- sourcing.sh
- source.sh
If you run shellcheck from project root it expects the sourcing.sh file to have
# shellcheck source=src/source.sh
BashSupport-Pro resolves the directive relative to the file it's in, so it expects:
# shellcheck source=../src/source.sh
So either the directive will fail for CLI shellcheck or for the plugin.
I think it's reasonable for the plugin to assume that shellcheck would be run from project root.
An additional setting to override this might be useful.
$ shellcheck --version
ShellCheck - shell script analysis tool
version: 0.9.0
license: GNU General Public License, version 3
website: https://www.shellcheck.net