cc @crazy-max ptal 🙂

Slightly concerned if this will start users expecting ~ to work everywhere; I know we had similar cases in the docker cli, where (by design), paths were expected to be absolute in various flags; also having only support on Linux can mean that the bakefile is no longer portable. But now could become a sliding slope, where (e.g.) %APPDIR% and other similar vars are also expected to work.

@thaJeztah that's a valid concern. For things like %APPDIR%, that's already supported via variables. There's just on syntactic sugar in the bake file format - you'd have to do $APPDIR, and then it should work (if set, as it would be on win)

I quite like the ~username syntax for things like builds though because it lets you map cache, output, etc without explicitly hardcoding the paths.

I agree with @thaJeztah that adding support for a tilde expansion is a bit of a slippery slope. Tilde expansions are generally done as part of the shell program and it isn't supported by most command line tools. This shows up in cases where --path=~/foo doesn't work but --path ~/foo will work because the first gets passed with ~ verbatim.

Recently, @crazy-max added a homedir() function to bake. I think it would be better and more explicit if we suggested something like this:

variable "HOME" {
 default = homedir()
}

Then HOME can be expanded consistently with everything else and we don't have to add any extra code or wade into trying to expand tilde symbols everywhere.