[DBD-SQLite] DBD::SQLite and CPAN

[David Dooling]

On Fri, Jun 19, 2009 at 12:20:23PM -0600, Curtis Jewell wrote:
> On Fri, 19 Jun 2009 18:45 +0100, "Ash Berlin" <ash_cpan at firemirror.com>
> wrote:
> > On 19 Jun 2009, at 18:37, David Dooling wrote:
> > > I am trying to clean up the prerequisites for a package that requires
> > > both DBI and DBD::SQLite (UR).  CPAN wants to order the prerequisites
> > > in alphabetical order, so it tries to install DBD::SQLite first.  It
> > > comes to this part of the DBD::SQLite Makefile.PL code
> > >
> > >  # Because DBI generates a postamble at configure-time, we need
> > >  # the required version of DBI very early.
> > >  my $DBI_required = 1.57;
> > >  eval {
> > >          require DBI;
> > >  };
> > >  if ( $@ or DBI->VERSION < $DBI_required ) {
> > >          print "DBI 1.57 is required to configure this module,  
> > > please install it or upgrade your CPAN/CPANPLUS shell\n";
> > >          exit(0);
> > >  }
> > >
> > > and fails (although the exit status is zero) because an older version
> > > of DBI is installed.  Even though DBI later appears and as PREREQ_PM
> > > in the WriteMakefile call, that line never gets executed, the Makefile
> > > never gets created, and CPAN will go no further with the DBD::SQLite
> > > install. CPAN does continue to try to install other modules,
> > > ultimately failing the requested install because DBD::SQLite is
> > > missing (or too old).
> > >
> > > I am not sure what the issue around the DBI postamble is so I am not
> > > sure how to fix this so DBD::SQLite to play nicely with CPAN.  Any
> > > ideas/guidance on how to get this to behave as one might expect?
> 
> The DBI postamble copies two files from the DBI distribution into the
> DBD driver's distribution - they're the standard framework for any XS
> dbd driver.
> 
> So the postamble is vital.

But if it were a PREREQ_PM, wouldn't it get installed before
DBD::SQLite gets built?  Or do those files need to be there before
even the Makefile is created?

> I would assume that there was an incompatible change or a necessary bug
> fix in one or the other of these two files in the 1.56 -> 1.57 era that
> would make compilation impossible, although I could be wrong. (It's
> quite possible:
> http://search.cpan.org/diff?from=DBI-1.56&to=DBI-1.57#Driver.xst - The
> postamble itself hasn't changed since 1.56, so it's not that.)
> 
> > Two possible solutions I can think of:
> > 
> > 1) configure_requires. Doesn't help with old clients
> 
> No, but it's the easiest way to help new ones. It can't hurt.

This seems more applicable to DBD::SQLite than something that needs
DBD::SQLite.  Using that would require porting the entire DBD::SQLite
build system to Module::Install (it currently uses
ExtUtils::MakeMaker).

> > 2) Use the 'Are we running under a CPAN shell' from the (now improved)  
> > Module::Install::AutoInstall.
> 
> Do this, too. It will catch what the previous one does not.

I'll try this (although I am not entirely sure if it will help; the
docs are a little light).

> > Oh, a bonus 3rd option.
> > 
> > 3) Remove the check and delay it to the first test which does BAIL_OUT  
> > if DBI is too old.
> 
> Does it even COMPILE if DBI is too old?

It seems if DBI is a PREREQ_PM, both of these are moot since the
appropriate version of DBI would be installed before compilation or
testing.

-- 
David Dooling