Autocomplete command-line flags with GHC 7.8.2

GHC 7.8.2 has been released just a few days ago¹. This is the first official release of GHC that contains my contributions. Most of them are improvements in the code generator and are thus practically invisible to most users. But I also implemented one very nice feature that will be useful to an average Haskeller. GHC now has --show-options flag that lists all command-line flags. This feature can be used to auto-complete command-line flags in shells that support this feature. To enable auto-completion in Bash add this code snippet to your ~/.bashrc file:

# Autocomplete GHC commands
_ghc()
{
    local envs=`ghc --show-options`
    # get the word currently being completed
    local cur=${COMP_WORDS[$COMP_CWORD]}

    # the resulting completions should be put into this array
    COMPREPLY=( $( compgen -W "$envs" -- $cur ) )
}
complete -F _ghc -o default ghc

From my experience the first completion is a bit slow but once the flags are cached things work fast.

Back