Bug#721547: libregexp-grammars-perl: Currently incompatible with Perl 5.18

[Salvatore Bonaccorso]

Hi,

Damian, CC'ing you only for information :)

On Sun, Sep 01, 2013 at 10:32:31PM +0200, Salvatore Bonaccorso wrote:
> Package: libregexp-grammars-perl
> Version: 1.028-1
> Severity: serious
> Tags: upstream
> Justification: maintainer decision, unfit for release with perl 5.18.1; incompatible
> 
> This is a blocking bug to prevent further migration of
> libregexp-grammars-perl into testing until some incompatibility
> problems with Perl 5.18 are solved upstream:
> 
> ,---- [ lib/Regexp/Grammars.pm ]
> | Warning: Regexp::Grammars is currently unsupported under Perl 5.18.
> |
> | Perl 5.18 changed how 'qr' constant overloadings are parsed and the
> | scope in which they are subsequently compiled. This change currently
> | make it impossible to reliably create 'qr' overloadings that inject
> | code blocks into a regex, as it prevents the overloaded regexes from
> | compiling properly in many cases, even with an explicit 'use re
> | "eval"' in scope.
> |
> | These problems have been reported, and the brave volunteers of P5P are
> | currently working on fixes. However, these will not be available until
> | at least 5.18.2.
> |
> | Because Regexp::Grammars relies on 'qr' overloads to inject code blocks
> | into regexes, the module is curently not compatible with Perl 5.18. It
> | may continue to work in some limited cases, but is no longer reliable.
> |
> | At present, if you rely on Regexp::Grammars for your parsing needs, your
> | alternatives are either not to upgrade to Perl 5.18, to livce with the
> | problems until they are resolved (in Perl 5.18.2, we hope), or else to
> | consider switching to another parsing system, such as Marpa.
> |
> | We deeply regret that Regexp::Grammars cannot currently be maintained
> | completelt due to these backwards-incompatible changes and bugs in
> | Perl 5.18.
> `----

I had the privilege to talk directly to Damian to aks about if it is
worth keeping Regexp::Grammars. Basically I would suggest the
following:

As we have from the RT ticket, there is slowly progress, and possibly
in some perl 5.18.x release it might be fixed the remaining problems,
basically around say 95% of it should work already now again.

I'm proposing the following: Keep Regexp::Grammars still in Debian
unstable. The release-critical Bug prevents the package migrating to
Debian Testing, so we will not ship libregexp-grammars-perl with a
Debian release which has perl 5.18.

The issues should be solved when working with Perl 5.20, which will
be released next month. Once this happens, a new version of
Regexp::Grammars will eventually be uploaded by Damian which changes
the warning to mark explicitly only the broken 5.18 releases.

Once we have Perl 5.20 in Debian libregexp-grammars-perl should be
safe to distribute again together in Debian as packaged module.

Thus in short: I'm in favour to keep the package for now with a RC bug
open preventing the migration to testing.

Regards,
Salvatore