fix: fix for Termux not having '/dev/stdin'

[bbigras]

Description

Use $BASH_VERSINFO to determine if source <(starship init bash --print-full-init) can be used.

This can only work if bash has $BASH_VERSINFO in 3.2.

Motivation and Context

To make eval "$(starship init bash)" work on Termux.

Closes #235

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Screenshots (if appropriate):

How Has This Been Tested?

• I have tested using MacOS
• I have tested using Linux
• I have tested using Windows

Checklist:

• I have updated the documentation accordingly.
• I have updated the tests accordingly.

[chipbuster]

[ "${{BASH_VERSINFO[0]}}" -ge 4 ] gives me bash: ${{BASH_VERSINFO[0]}}: bad substitution on MacOS :(

I assume there was a reason you elected not to go for single curly-braces?

[bbigras]

Did you copy paste that from the code to a terminal? I had to escape those because I'm using the format macro.

It should not be double at runtime.

[chipbuster]

@bbigras Yes, yes I did.

Sorry, hasn't been the best day for me.

[chipbuster]

Code looks good to me, and works in a bash 3.2 shell on MacOS.

I'd like to get some confirmation that the process substitution syntax does work on Bash 4.0. Have you tested with that version? The SO post in the comments mentions that it's a bash 3.2 limitation, but the post they link to on the bash mailing lists only says that this is a limitation that will be lifted "someday."

[chipbuster]

@bbigras Bad news: on bash-4.0 on my Linux machine, it doesn't work. Displays the same behavior as it does in 3.2, namely it looks like a no-op.

It does work for bash-5.0 on my machine, so I guess we just need to bisect minor versions until we find the first working one. I'll take a crack at it tomorrow--I actually downloaded all the source archives for various bash versions for testing exactly this kind of stuff, but I haven't gotten around to actually building them yet.

[bbigras]

Sorry, hasn't been the best day for me.

No worries. Thanks for testing.

I'd like to get some confirmation that the process substitution syntax does work on Bash 4.0.

I tested it successfully on 4.4.23(1)-release on NixOS.

It does work for bash-5.0 on my machine, so I guess we just need to bisect minor versions until we find the first working one. I'll take a crack at it tomorrow--I actually downloaded all the source archives for various bash versions for testing exactly this kind of stuff, but I haven't gotten around to actually building them yet.

Termux has Bash 5 so we could just test for >= 5 if you want. I guess it could be a good idea to figure out which minor version fixes it.

[chipbuster]

@bbigras On linux, the earliest version it works with is bash 4.1. Your call--we can either look specifically for that version or we can just go for 5.0 and up.

[bbigras]

I updated the PR to check for 4.1. I hope I did it right.

[chipbuster]

After further testing, it seems that neither init system works correctly for bash-4.0. The shell acknowledges that PROMPT_COMMAND is set to starship_precmd, and it even executes the line that alters PS1, but then the prompt never actually changes.

Given that that's not within the scope of this PR, I went ahead and reverted the version change (just so that it's easier to tell what's going on), and we can open an issue if bash-4.0 support is ever important to anyone.

Thanks for the work, and sorry about the complications of testing! Every time I wander into shell-land, it seems things become more complex than they used to be.