opam env toxic for fish shell

[mro]

over at ocaml/dune#6907 it turned out that the dune crash is triggered by a fishy $PATH from opam env. A typical output looks like

$ opam env
set -gx OPAM_SWITCH_PREFIX '/Users/mro/.opam/4.12.1';
set -gx CAML_LD_LIBRARY_PATH '/Users/mro/.opam/4.12.1/lib/stublibs:/Users/mro/.opam/4.12.1/lib/ocaml/stublibs:/Users/mro/.opam/4.12.1/lib/ocaml';
set -gx OCAML_TOPLEVEL_PATH '/Users/mro/.opam/4.12.1/lib/toplevel';
set -gx PKG_CONFIG_PATH '/Users/mro/.opam/4.12.1/lib/pkgconfig';
set -gx PATH ':/Users/mro/.opam/4.12.1/bin' '/opt/homebrew/bin' '/bin' '/sbin' '/usr/bin' '/usr/sbin' '/usr/local/bin' '/usr/local/MacGPG2/bin' '/Users/mro/bin';

The leading colon : is an issue as well as occasionally keeping . in the $PATH.

Shell is fish, version 3.6.0, seen on a macbook Air M1.

A workaround is to use

$ eval (opam env | sed -e "s/':/'/g;s/'\.'//g")

# opam config report
# opam-version      2.0.7 (4c1704d6a1a879625a132fbe4f1bb207965700b0)
# self-upgrade      no
# system            arch=arm64 os=macos os-distribution=homebrew os-version=11.7.4
# 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) (default repo at 2370128e)
# pinned            0
# current-switch    4.12.1

[rjbou]

This was fixed in 2.0.8 & 2.1.

[mro]

thanks @rjbou
my opam is ages old!

I am surprised that opam hasn't self-upgraded since. Shouldn't it? How can I find out why?

[mro]

(doing a manual https://opam.ocaml.org/doc/Install.html)