detect shell is fish in executable for auto-complete

[Aaron Turner]

fish, version 3.7.1
Darwin 23.4.0

TL;DR: I am the author of aws-sso-cli and I would like to add tab auto-completion for fish. I'm running into an issue due to how fish is different from bash and zsh regarding how it processes : as an argument value.

Specifically, I'll have a command like aws-sso exec -p <profile name> where <profile name> is often in the format of <AWS Account Alias>:<AWS IAM Role Name>. When I generate the list of possible values for -p for bash or zsh, I must escape it to be like fooAccount\:barProfile. But fish seems to require there to be no escaping of the semi-colon because it's not a word delim maybe?

If I use os.Getenv("FISH_VERSION") it evaluates to an empty string, because I believe it is not actually exported: #374

Or perhaps I'm just doing it wrong in my aws-sso.fish file?

Are there any options available to me?

[Fabian Boehm]

When you generate a completion script from your tool, you would typically just pass the shell as an argument. E.g. pip wants

pip3 completion --fish

Now, when you generate the list of candidates, I would usually just print the candidates, and then handle the parsing of that in the shell, e.g. let the bash/zsh scripts escape what they need to have escaped. Print the simplest format you can and let the shell handle shell-specific concerns.

If you can't do that, you'd have to either unescape the argument in fish, e.g.

aws-sso exec -p <profile name> | string replace -ra '\\\:' ':'

or add a flag to indicate it shouldn't escape:

aws-sso exec -p <profile name> --no-escape-colons

(or call it --fish, or set an exported variable like FISH_MODE=1 aws-sso and check that)

[Aaron Turner]

Thanks. That works. That said, there doesn't seem to be any means of auto-detecting fish which is annoying. Means my users have to manually specify --shell=fish to install the auto-complete file.