opam 2.0.4 clobbers MANPATH on fish

[talex5]

There needs to be a leading : in MANPATH so that the default paths are still used. It seems that opam does this for other shells, but not for fish:

~ $ opam config env --shell=bash | grep MANPATH
MANPATH=':/home/user/.opam/4.07.0/man'; export MANPATH;
~ $ opam config env --shell=zsh  | grep MANPATH
MANPATH=':/home/user/.opam/4.07.0/man'; export MANPATH;
~ $ opam config env --shell=fish | grep MANPATH
builtin -n | /bin/sh -c 'grep -q \'^argparse$\'' 1>/dev/null 2>/dev/null; and
set -gx MANPATH '/home/user/.opam/4.07.0/man';

The result is e.g.

~ $ man ls
No manual entry for ls

(see also #3319)

~ $ opam config report
# opam config report
# opam-version      2.0.4 
# self-upgrade      no
# system            arch=x86_64 os=linux os-distribution=debian os-version=10
# 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              3
# repositories      1 (http), 1 (version-controlled) (default repo at 1b1f3945)
# pinned            13 (git), 1 (rsync)
# current-switch    4.07.0

[rjbou]

Thanks for the report.
What is your fish version ? It seems related to #3728.
/cc @gregory-nisbet

[talex5]

~ $ fish --version
fish, version 3.0.2

But you don't need fish installed to see the bug. Just do opam config env --shell=fish | grep MANPATH and you can see that the : is missing ('/home/opam/.opam/4.07/man' should be ':/home/opam/.opam/4.07/man').

[talex5]

Thanks. BTW, I noticed that man on opam-installed binaries works fine even without MANPATH being set. Running man -d, I see:

path directory /home/user/.opam/4.07.0/bin is not in the config file
but does have a ../man, man, ../share/man, or share/man subdirectory
adding /home/user/.opam/4.07.0/man to manpath

This is on Debian 10; I don't know how widespread this feature is.

[robin-a-meade]

I just wanted to note for any future MANPATH troubleshooters that the output of manpath -d no longer includes the helpful but does have a ../man, man, ../share/man, or share/man subdirectory text. It was removed in the following commit:

https://git.savannah.nongnu.org/cgit/man-db.git/commit/?id=8197d7824f814c5d4b992b4c8730b5b0f7ec589a

(Mirrored here:
qunixorg/man-db@8197d78#diff-af71d1fb8a7162c40d7e7e3d62679bc5fa7ffce53d20966998b0f3e66af1ade6 )

The comment by @talex5 above helped me figure out what was going on. Thanks!