perl-functions.eclass: add perl_get_module_version

This utility provides informational data describing the given module
names state of installation, either as a version, or as an error
message describing the grade of failure incurred in module loading.

It has the side effect that it most load the module (and its
dependencies) into memory to give a report value, and can be expensive
and have side-effects from Perl code execuring while the module loads,
including (but not limited to) people calling POSIX::_exit

This is the slowest way of inspecting state about a module, as
it must load the module

diff --git a/eclass/perl-functions.eclass b/eclass/perl-functions.eclass
index de22f4757a444c3ed4976bbe8de1637e2157e951..be27d7e2509d763d7ca194cde639f301d8712c6b 100644 (file)
--- a/eclass/perl-functions.eclass
+++ b/eclass/perl-functions.eclass
@@ -379,3 +379,54 @@ perl_has_module_version() {
                } ? 0 : 1 )' "$@"
 }
 
+# @FUNCTION: perl_get_module_version
+# @USAGE: MODVER=$(perl_get_module_version "Test::Simple")
+# @DESCRIPTION:
+# Query the installed system perl to report the version of the installed
+# module.
+#
+# Note this should be strictly for diagnostic purposes to the end user,
+# and may be of selective use in pkg_info to enhance
+# emerge --info reports.
+#
+# Anything that does version comparisons **must not** use the return value
+# from this function
+#
+# Also note that this **must** at least attempt load the module in
+# question as part of its operation, and is subsequently prone to SLOWness.
+#
+# Return codes return error in both compilation-failure and not-installed cases.
+
+perl_get_module_version() {
+       debug-print-function $FUNCNAME "$@"
+
+       [[ $# -gt 0 ]] || die "${FUNCNAME}: No module name provided"
+       [[ $# -lt 2 ]] || die "${FUNCNAME}: Too many parameters ($#)"
+
+       if ! perl_has_module "$@" ; then
+               echo "(Not Installed)";
+               return 1;
+       fi
+
+       # Todo: What do we do if require fails? spew to stderr
+       # or stay silent?
+
+       perl -we 'my $mn = $ARGV[0];
+               $mn =~ s{(::|\x{27})}{/}g;
+               local $@;
+               eval { require qq[${mn}.pm]; 1 } or do {
+                       print q[(Compilation failed in require)];
+                       exit 1;
+               };
+               my $stash = \%{ $ARGV[0] . q[::] };
+               if ( not exists $stash->{VERSION} ) {
+                       print q[(No VERSION property)];
+                       exit 0;
+               }
+               if ( not defined ${$stash->{VERSION}} ) {
+                       print q[(undef)];
+                       exit 0;
+               }
+               print ${$stash->{VERSION}};
+               exit 0; ' "$@"
+}