Re: [PATCH] get_maintainer: lazy load JSON::PP only when --json is used

[Joe Perches <joe@perches.com>]

On Fri, 2026-10-30 at 22:44 +0100, Oleg Nesterov wrote:
> On 10/30, Joe Perches wrote:
> > On Fri, 2026-10-30 at 17:17 +0100, Oleg Nesterov wrote:
> > > > > This module is only needed with the --json option. Use "require" to
> > > > > load this module dynamically inside the "if ($json)" block instead.
> > > > The patch may be sensible but could fail the same way
> > > > if you used the --json option with your version.
> > > Of course, "./scripts/get_maintainer.pl --json ..." will still fail
> > > the same way without JSON::PP. But with this patch get_maintainer.pl
> > > works without the --json option.
> > What does that failure output?
> Hmm. I am not sure I understand you concerns. Let me add more details.
> So, I think this patch makes no difference if JSON::PP is installed.
> Do you agree?
> 
> Now lets see what happens on my machine where JSON::PP is NOT installed.
> Without --json:
> 
> Before this patch:
> 
> 	$ ./scripts/get_maintainer.pl ./scripts/get_maintainer.pl
> 	Can't locate JSON/PP.pm in @INC (you may need to install the JSON::PP module) (@INC entries checked: /usr/local/lib64/perl5/5.42 /usr/local/share/perl5/5.42 /usr/lib64/perl5/vendor_perl /usr/share/perl5/vendor_perl /usr/lib64/perl5 /usr/share/perl5) at ./scripts/get_maintainer.pl line 24.
> 	BEGIN failed--compilation aborted at ./scripts/get_maintainer.pl line 24.
> 
> After:
> 
> 	$ ./scripts/get_maintainer.pl ./scripts/get_maintainer.pl
> 	Joe Perches <[joe@perches.com](mailto:joe@perches.com)> (maintainer:GET_MAINTAINER SCRIPT)
> 	[linux-kernel@vger.kernel.org](mailto:linux-kernel@vger.kernel.org) (open list)
> 
> With --json:
> 
> Before this patch:
> 
> 	$ ./scripts/get_maintainer.pl --json ./scripts/get_maintainer.pl
> 	Can't locate JSON/PP.pm in @INC (you may need to install the JSON::PP module) (@INC entries checked: /usr/local/lib64/perl5/5.42 /usr/local/share/perl5/5.42 /usr/lib64/perl5/vendor_perl /usr/share/perl5/vendor_perl /usr/lib64/perl5 /usr/share/perl5) at ./scripts/get_maintainer.pl line 24.
> 	BEGIN failed--compilation aborted at ./scripts/get_maintainer.pl line 24.
> 
> After:
> 
> 	$ ./scripts/get_maintainer.pl --json ./scripts/get_maintainer.pl
> 	Can't locate JSON/PP.pm in @INC (you may need to install the JSON::PP module) (@INC entries checked: /usr/local/lib64/perl5/5.42 /usr/local/share/perl5/5.42 /usr/lib64/perl5/vendor_perl /usr/share/perl5/vendor_perl /usr/lib64/perl5 /usr/share/perl5) at ./scripts/get_maintainer.pl line 665.
> 
> Same failure. Sorry, I don't understand what is not clear for you :(
> 
> 
> > Dunno.  Depending on the current failure output
> > maybe adding something like the below is better:
> > 
> > use Module::Load::Conditional qw(check_install);
> > 
> > if (!check_install(module => 'JSON:PP')) {
> >     die "$P: --json not available - missing perl module JSON:PP\n";
> > }
> 
> But why? Why make get_maintainer.pl depend on yet another module?
> FYI, on my Fedora 44
> 
> 	$ perl -we 'use Module::Load::Conditional qw(check_install);'
> 	Can't locate Module/Load/Conditional.pm in @INC (you may need to install the Module::Load::Conditional module) (@INC entries checked: /usr/local/lib64/perl5/5.42 /usr/local/share/perl5/5.42 /usr/lib64/perl5/vendor_perl /usr/share/perl5/vendor_perl /usr/lib64/perl5 /usr/share/perl5) at -e line 1.
> 	BEGIN failed--compilation aborted at -e line 1.

Module::Load is a core perl module since 5.10 and

I think you are using a broken version of a perl installation
and I think you should:

$ sudo dnf install perl-core

> And for what ???

My idea is to make it more obvious _why_ something fails
and not like get_maintainer itself is broken.

> If we want to "improve" the errmsg, we can use "eval { require JSON::PP; }; die ... if $@"
> but this looks absolutely pointless to me.

We disagree.  I prefer output errors to look less broken.