Add default value to unset environment variables

[erikeah]

Similar to how it's been done in bash, this allows to give dafault values to environment variables that hasn't been set yet.

Test plan:

• Test the old syntax by using ${ENVVAR}, expect to behave the same way.
• Test the new syntax by using ${ENVVAR:foobar}, expect to use the value after the semi-colon if the environment variable has not been set.

Congrats for such a cool project, Ain is just what I have been looking for. 💝

[jonaslu]

Hey, thanks for the kind words.

I'll have a think if ain should support sh-isms such as variable defaults. If we go this route then probably all bash-variable antics should be supported too. Need to read up on that.

In the meantime you can work around it by defining an .env file supplying the defaults there.

[erikeah]

By bash variables antics, do you mean what's called in the bash manual «Expansion»?

In that case I think Ain it could have a lot methods to transform environment variables. However I see too much methods, I don't see anyone using all that features (or knowing how to use it), also maintain all those lines... and ensure code quality... pain increasing

I think a well being selected, or inspired by, those features of shell inside a Ain could be cool but just a few, or even anyone. 😂

But I think a default value for env vars could be useful, maybe changing the nomenclature will make you more confortable?

Thanks for response!

[jonaslu]

Yes that's what I mean with bash-antics.

I've thought some more about it, and this is not the way to go.

With this syntax you can define the same variable twice with different defaults (thanks to @meros for pointing this out). That will be confusing and bug prone, esp. if several files are used.

VAR:value is a valid env-variable, you can define it via env but not in bash itself. This will cause regression in any files using this as the actual variable.

[erikeah]

Thanks @meros, I haven't notice on env... To be fair, I haven't ever used.

I will try to get some documentation on illegal symbols on Environment Variables, from that I will craft some posible syntax to present to you and may one of them will fit on ain!

[jonaslu]

Allright, good luck!

I'll close this PR.