Backport the build_class stuff

git-svn-id: http://svn.perl.org/modules/Module-Build/branches/release-0_26_branch@5378 50811bd7-b8ce-0310-adc1-d9db26280581

Changes

@@ -5,6 +5,11 @@ Revision history for Perl extension Module::Build.
  - Fix the output of an informational message that we output when
    changing the 'shebang line' in installable scripts. [Robin Barker]
 
+ - Backported a change from the 0.27_xx branch that keeps track of any
+   custom Module::Build subclass that might have been created in the
+   Build.PL script, so that we can reinstantiate the right class in
+   new_from_context(). [Requested by Jos Boumans]
+
 0.2610  Fri Apr 15 08:25:01 CDT 2005
 
  - new_from_context() was losing its arguments in some cases (and not

lib/Module/Build/Base.pm

@@ -37,6 +37,21 @@ sub resume {
 
   $self->read_config;
 
+  # If someone called Module::Build->current() or
+  # Module::Build->new_from_context() and the correct class to use is
+  # actually a *subclass* of Module::Build, we may need to load that
+  # subclass here and re-delegate the resume() method to it.
+  unless ( UNIVERSAL::isa($self, $self->build_class) ) {
+    my $build_class = $self->build_class;
+    my $config_dir = $self->config_dir || '_build';
+    my $build_lib = File::Spec->catdir( $config_dir, 'lib' );
+    unshift( @INC, $build_lib );
+    unless ( $build_class->can('new') ) {
+      eval "require $build_class; 1" or die "Failed to re-load '$build_class': $@";
+    }
+    return $build_class->resume(@_);
+  }
+
   unless ($self->_perl_is_same($self->{properties}{perl})) {
     my $perl = $self->find_perl_interpreter;
     warn(" * WARNING: Configuration was initially created with '$self->{properties}{perl}',\n".
@@ -98,9 +113,11 @@ sub _construct {
 				   %input,
 				  },
 		   }, $package;
-
+  
   my ($p, $c) = ($self->{properties}, $self->{config});
 
+  $p->{build_class} ||= ref $self;
+
   # The following warning could be unnecessary if the user is running
   # an embedded perl, but there aren't too many of those around, and
   # embedded perls aren't usually used to install modules, and the
@@ -419,6 +436,7 @@ EOF
   # XXX huge hack alert - will revisit this later
   my %valid_properties = map {$_ => 1}
     qw(
+       build_class
        module_name
        dist_name
        dist_version