No expansion of nested environment variables in environment variable overrides

[6b6279]

Hello,

I am not sure if this is a shortcoming of Flatpak itself, but it seems like nested envvars in envvar overwrites are not evaluated, e.g., the overwrite MYDATADIR=$XDG_DATA_HOME/custom isn't evaluated into MYDATADIR=/home/foo/.var/app/foo.bar.Example/data/custom, but according to flatpak run --command=sh --devel, it's declared literally, so that the variable literally contains the substring $XDG_DATA_HOME.

I've discovered this trying to set DOOMWADDIR for Crispy Doom: fabiangreffrath/crispy-doom#1193

[rusty-snake]

There is no concept of "nested environment variables" in POSIX (i.e. setenv(3)/getenv(3)). They are plain strings w/o any logic/runtime beyond <NAME>=<VALUE>. FOOBAR=$FOO/bar in bash works because the right side is evaluated with features such as "parameter expansion" or "command substitution".

Flatseal could (=technically possible) expand those variables at the time when you enter/save them but not when you flatpak run. This is likely not what you want since you could also just enter the expanded path. (And $XDG_DATA_HOME might have an unexpected value due to flatpak).

As you already said, this limitation comes from flatpak. Where I could find two relevant issues:

flatpak/flatpak#4596
flatpak/flatpak#1415

[6b6279]

I see. Like you said, if Flatseal were to expand envvars upon "entry" (e.g., string replacement in the entry field), it'd cause other issues, ex., $XDG_DATA_HOME being incorrectly replaced. I guess I am better off manually typing in the exact paths.