Canonicalize source path

[rylev]

This allows users to have "~/some/path/../to/binary" as their source in their spin.toml.

[lann]

You'll have to rebase on main...sorry!

[lann]

Not sure how I feel about this feature; '~'-expansion is usually just a shell feature and while there are some applications that support it, it isn't really all that common in config files ime. I would rather spell out /home/lann/... so that I'm more likely to catch it when reviewing a diff...

[rylev]

Perhaps I should explain why I'd like to have this feature. My cargo target directory is always set to .cargo_target directory in my home directory. When I switch back and forth between Linux and macOS I have to constantly adjust the source path to fit the machine I'm on. With this feature, I wouldn't have to adjust since it's always in the same place relative to my home directory.

Perhaps you could explain more about what you're worried about? Do we want to discourage source paths that aren't relative to spin application? We already support absolute paths, so I see this as just an extension of that.

[lann]

It's partly about consistency. Do we support ~ just in source paths? Should we support ~<user> too? Why just ~-expansion and not e.g. $HOME?

[lann]

But! Your use case seems reasonable to me and I'm definitely not vetoing this or anything.

[rylev]

@lann I expanded this PR to also support ENV variables using the shellexpand crate. Unfortunately that crate does not support ~$USER expansion, but I don't think that feature is used super often so perhaps that's fine (at least for now)?

[lann]

👍 The only other thing I would consider is whether we want to support ~ in runtime config for consistency here. I can't think of anywhere else it would apply.

[rylev]

@lann that would need to be reconciled with how we handle sqlite databases as well. Can we merge this first and then handle the runtime config case once the sqlite PR lands? I will make an issue for this.

[rylev]

I opened #1526 to track that we do this consistently.

[lann]

Sorry, had this review comment queued up but never submitted it...