Flag Parsers in Various Languages - oils-for-unix/oils GitHub Wiki
Many of these generate bash completions. It would be nice if they could target Shellac somehow and get support for bash, zsh, fish, Oil, etc.
- Python: argcomplete for the stdlib argparse module
- Go: cobra, has the ability to generate bash completions.
- Rust: clap-rs
- Haskell: bash completion for optparse-applicative
- Ruby: Fylla -- for the Thor command line toolkit
- google gflags for C++, Java, etc. ?