opam env adds . to PATH in fish shell

[bbc2]

When I execute eval (opam env), I end up with . in my PATH.

I think the problem is caused by an extra colon in the output of opam env:

set -gx PATH ':/home/bertrand/.opam/4.07.1/bin' '/usr/local/sbin' '/usr/local/bin' '/usr/bin' '/usr/bin/site_perl' '/usr/bin/vendor_perl' '/usr/bin/core_perl';

It results in:

> echo $PATH
. /home/bertrand/.opam/4.07.1/bin /usr/local/sbin /usr/local/bin /usr/bin /usr/bin/site_perl /usr/bin/vendor_perl /usr/bin/core_perl

opam config report

# opam config report
# opam-version      2.0.6 
# self-upgrade      no
# system            arch=x86_64 os=linux os-distribution=arch os-version=unknown
# solver            builtin-mccs+glpk
# install-criteria  -removed,-count[version-lag,request],-count[version-lag,changed],-changed
# upgrade-criteria  -removed,-count[version-lag,solution],-new
# jobs              7
# repositories      1 (http), 1 (version-controlled) (default repo at 203e326c)
# pinned            1 (git), 1 (rsync)
# current-switch    4.07.1

[rjbou]

It comes from #3878: for MANPATH that leading ':' is needed (#3878). Seems that should be restrained only to MANPATH, and not added for PATH & CDPATH as they are completely redefined.

[rjbou]

Thanks for the report!

[undu]

I've encountered this issue since I prefer per-session switches so I though sharing my workaround to whoever finds this thread.

I use a function to wrap switch activation (in $XDG_CONFIG_HOME/fish/functions/oswitch.fish):

function oswitch
    if test (count $argv) -lt 1
        echo "oswitch: expected a least an arg, got none"
        echo "Usage: oswitch <switch>"
        return -1
    end
    set switch "$argv[1]"
    if opam switch set --dry-run "$switch" 2> /dev/null > /dev/null
        eval (opam env --switch="$switch" --set-switch)
        # opam adds . to PATH, delete it if it's present
        if set -l i (contains -i -- '.' $PATH)
                set -e PATH[$i]
        end
    else
        # show output
        opam switch set --dry-run "$switch"
    end
end

The recommended way to add paths to fish is to append paths to $fish_user_paths instead of directly setting the $PATH, but I don't know how well that meshes with cross-shell handling in opam. Adding a path would be usually done with contains $path $fish_user_paths; or set -a fish_user_paths $path