Misc #17815


Snapcraft Ruby plugin

Added by paddor (Patrik Wenger) about 1 year ago. Updated about 1 year ago.



I'm working on a Ruby build plugin for the Snapcraft v2 plugin AP, since the v1 Ruby plugin does not work on the Ubuntu core20 image. The v2 API only allows to influence the build step, which means there's no nice way for the plugin to set environment variables that apply during runtime. The problem is that the final paths to Ruby's stdlib are unknown during compile time.

I've got it to work by renaming the ruby executable to ruby.bare and creating a wrapper script ruby that sets the $RUBYLIB and $GEM_PATH env variables based on $SNAP before execing ruby.bare. I don't like that it requires a wrapper script though, since it would have to awkwardly determine the arch-specific stdlib directory to support any platform. The current wrapper script is this:

export RUBYLIB="$SNAP/lib/ruby/snap:$SNAP/lib/ruby/snap/x86_64-linux:$RUBYLIB"
export GEM_PATH="$SNAP/lib/ruby/gems/snap:$GEM_PATH"

exec `dirname $0`/ruby.bare "$@"

What possible solutions are there? I could maybe fix the shebangs of Ruby executables like gem and bundle, but not ruby itself since it's binary. Also, I'm not sure if env variable expansion even works in shebang.
Can the configure script's --with-search-path be made to support env variable expansion during runtime? That still wouldn't solve the issue about the arch-specific directory.

Python apparently determines its load paths relative to the executable being run. Does Ruby support anything like that?

Any other ideas?
Current state:


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