haskell-prompt-info (zsh)

haskell-prompt-info.zsh

function haskell_info() {
    cabal_files=(*.cabal(N))
    if [ $#cabal_files -gt 0 ]; then
        if [ -f cabal.sandbox.config ]; then
            cabal_sandbox_info
        elif [ -f stack.yaml ]; then
            stack_info
        else
            echo "%{$fg[red]%}no stack/sandbox%{$reset_color%}"
        fi
    fi
}

function stack_info() {
    ghc_version=`ghc --version | rev | cut -d' ' -f 1 | rev`
    resolver_yaml=`cat stack.yaml | grep resolver | cut -d' ' -f 2`
    if [ -d ".stack-work/install/x86_64-linux/$resolver_yaml" ]; then
        ghc_stack=`ls .stack-work/install/x86_64-linux/$resolver_yaml/ | grep $ghc_version`
        if [ $ghc_stack ]; then
            echo "[%{$fg[green]%}$resolver_yaml %{$reset_color%}| %{$fg[green]%}$ghc_version%{$reset_color%}]"
        else
            ghc_stack=`ls .stack-work/install/x86_64-linux/$resolver_yaml/ | xargs`
            echo  "[%{$fg[green]%}$resolver_yaml%{$reset_color%}|%{$fg[red]%}$ghc_stack%{$reset_color%}]"
        fi
    else
        echo  "%{$fg[red]%}[$resolver_yaml missing please do a 'stack build']%{$reset_color%}"
    fi
}

function cabal_sandbox_info() {
    ghc_version=`ghc --version | rev | cut -d' ' -f 1 | rev`
    ghc_loc=`ls .cabal-sandbox | grep ghc | cut -d'-' -f 4 | grep $ghc_version`
    if [ $ghc_loc ]; then
        echo "[%{$fg[green]%}$ghc_version%{$reset_color%}]"
    else
        ghc_version=`ls .cabal-sandbox | grep ghc | cut -d'-' -f 4 | xargs`
        echo  "[%{$fg[red]%}$ghc_version%{$reset_color%}]"
    fi
}

RPROMPT="\$(haskell_info) $RPROMPT"

cabal sandboxes are indicated by a ghc version liked [7.10.2]

• green ghc version indicates that there is a cabal project, and there exists a directory in the sandbox with libraries built with the current ghc (in the path)
• a list of red ghc versions indicates cabal projects, which would be available

for stack projects the indicator is like: [rts-3.0|7.10.0]

• green resolver info and green ghc version indicate a proper stack project
• red resolver info indicate that the current resolver is not initialized

the default choice if both cabal-sandbox and a stack project are coexisting is cabal for stack is quite new and there are more cabal projects out there

Note: stack itself is a moving target and changes in stack might lead to a breakage in this script
Note: this setup has been made on a linux machine - if you are working on a mac/windows it might need some adjustments.