weechat multiline.pl broken due to legacy Pod::Select being remove from perl

[yipengsun]

Describe the bug
I've been using multiline.pl in weechat for multi-line message support. After updating to NixOS 20.09 and weechat 2.9, the script no longer works.

When trying to load that script, weechat had the following error:

2020-12-10 02:38:00		perl: error: Can't locate Pod/Select.pm in @INC (you may need to install the Pod::Select module) (@INC contains: /nix/store/ifayp0kvijq0n4x0bv51iqrb0yzyz77g-perl-5.32.0/lib/perl5/site_perl/5.32.0/x86_64-linux-thread-multi /nix/store/ifayp0kvijq0n4x0bv51iqrb0yzyz77g-perl-5.32.0/lib/perl5/site_perl/5.32.0 /nix/store/ifayp0kvijq0n4x0bv51iqrb0yzyz77g-perl-5.32.0/lib/perl5/5.32.0/x86_64-linux-thread-multi /nix/store/ifayp0kvijq0n4x0bv51iqrb0yzyz77g-perl-5.32.0/lib/perl5/5.32.0) at /home/syp/.weechat/perl/autoload/multiline.pl line 240.
2020-12-10 02:38:00		perl: error: Can't locate Pod/Select.pm in @INC (you may need to install the Pod::Select module) (@INC contains: /nix/store/ifayp0kvijq0n4x0bv51iqrb0yzyz77g-perl-5.32.0/lib/perl5/site_perl/5.32.0/x86_64-linux-thread-multi /nix/store/ifayp0kvijq0n4x0bv51iqrb0yzyz77g-perl-5.32.0/lib/perl5/site_perl/5.32.0 /nix/store/ifayp0kvijq0n4x0bv51iqrb0yzyz77g-perl-5.32.0/lib/perl5/5.32.0/x86_64-linux-thread-multi /nix/store/ifayp0kvijq0n4x0bv51iqrb0yzyz77g-perl-5.32.0/lib/perl5/5.32.0) at /home/syp/.weechat/perl/autoload/multiline.pl line 240.
2020-12-10 02:38:00		BEGIN failed--compilation aborted at /home/syp/.weechat/perl/autoload/multiline.pl line 240.
2020-12-10 02:38:00	=!=	perl: function "register" not found (or failed) in file "/home/syp/.weechat/perl/autoload/multiline.pl"
2020-12-10 02:38:00		perl scripts loaded: highmon
2020-12-10 02:38:00		Plugins loaded: alias, buflist, charset, exec, fifo, fset, irc, logger, lua, perl, python, relay, script, spell, trigger, xfer
2020-12-10 02:38:00		python: loading script "/nix/store/mx91fb7q7vfvc0zc4l8fx9amhyq1nrcd-wee-slack-2.6.0/share/wee_slack.py"
2020-12-10 02:38:00		python: registered script "slack", version 2.6.0 (Extends weechat for typing notification/search/etc on slack.com)
2020-12-10 02:38:00		Connecting to 2 slack teams.
2020-12-10 02:38:49		fifo: pipe closed

To Reproduce
Steps to reproduce the behavior:

1. Download the multiline.pl from the official weechat repo
2. Make sure it's on NixOS 20.09 with weechat 2.9
3. Copy the script to $HOME/.weechat/perl/autoload

Expected behavior
No error message on weechat startup, and the multi-line message works

Additional context
I found this issue is already reported at weechat/scripts#421. On Arch linux, this seems to be solved by install the Pod::Select manually.

Notify maintainers

@lovek323 @lheckemann

Metadata
Please run nix-shell -p nix-info --run "nix-info -m" and paste the result.

 - system: `"x86_64-linux"`
 - host os: `Linux 5.9.12, NixOS, 20.09.2152.e34208e1003 (Nightingale)`
 - multi-user?: `yes`
 - sandbox: `yes`
 - version: `nix-env (Nix) 2.3.9`
 - channels(root): `"nixos-20.09.2152.e34208e1003"`
 - nixpkgs: `/nix/var/nix/profiles/per-user/root/channels/nixos`

Maintainer information:

# a list of nixpkgs attributes affected by the problem
attribute:
# a list of nixos modules affected by the problem
module:

[aanderse]

This script should probably be packaged for nixpkgs so it can have a proper perl environment. @stigtsp any thoughts on that? You wouldn't happen to be a weechat user, would you?

[stigtsp]

Pod::Select is provided by perlPackages.PodParser, you can get a nix-shell which includes this module in @INC by using nix-shell -p 'perl.withPackages(p:[p.PodParser])'

In the case of weechat you can do something like this to get a Perl which includes this module:

    (weechat.override {
      configure = { availablePlugins, ...}: {
        plugins = with availablePlugins; [
          (perl.withPackages(p: [ p.PodParser ]))
        ];
      };
    })

[yipengsun]

Thanks. I was able to get multiline.pl work again by overriding weechat in an overlay to add PodParser to perl:

   weechat = super.weechat.override {
    configure = { availablePlugins, ... }: {
      plugins = with availablePlugins; [
        (perl.withPackages (p: [ p.PodParser ]))
      ] ++ [ python ];
      scripts = with super.weechatScripts; [
        wee-slack
      ] ++ self.stdenv.lib.optionals (!self.stdenv.isDarwin) [ weechat-notify-send ];
    };
  };

Edit: Hopefully for better clarity.

[krzkrzkrz]

Im consfused, and for better clarity for others who come across the same issue. What is the solution exactly?

[krzkrzkrz]

For those wondering, on Arch, one should install perl-pod-parser. Also highlighted https://wiki.archlinux.org/index.php/WeeChat#Problem_loading_multiline.pl

[yipengsun]

My solution is to override weechat in an overlay. The relevant lines are these:

      plugins = with availablePlugins; [
        (perl.withPackages (p: [ p.PodParser ]))
      ] ++ [ python ];

Make sure you list all types of plugins (e.g. Perl and Python) that you intent to use, as this overrides that setting, instead of append to default values.

[codybuell]

On OSX installing Pod::Parser with cpan did the trick:

brew install perl
cpan install Pod::Parser