Nobody (I know) that uses fish actually writes scripts in fish. Everyone writes scripts in bash for portability.

I’ve used fish for a half decade too, I still write my scripts in bash like everyone else. I want them to be standard and portable.

Longer scripts get the Python treatment or a Go application.

While there is a tool called `babelfish` that will automatically convert bash to fish, in practice it's rarely needed.

You can run bash scripts from fish.

For sourcing, often it makes sense to use direnv to automatically load variables. -- For "just source this one time", in the worst case you can run a bash shell, source that, then run a fish shell.

You can always run .sh scripts