if.pm is upstream blead

2 files changed, 93 insertions, 0 deletions

diff --git a/dist/if/if.pm b/dist/if/if.pm
new file mode 100644
index 0000000000..5f6bcc8ae1
--- /dev/null
+++ b/dist/if/if.pm
@@ -0,0 +1,56 @@
+package if;
+
+$VERSION = '0.05';
+
+sub work {
+  my $method = shift() ? 'import' : 'unimport';
+  die "Too few arguments to `use if' (some code returning an empty list in list context?)"
+    unless @_ >= 2;
+  return unless shift;		# CONDITION
+
+  my $p = $_[0];		# PACKAGE
+  (my $file = "$p.pm") =~ s!::!/!g;
+  require $file;		# Works even if $_[0] is a keyword (like open)
+  my $m = $p->can($method);
+  goto &$m if $m;
+}
+
+sub import   { shift; unshift @_, 1; goto &work }
+sub unimport { shift; unshift @_, 0; goto &work }
+
+1;
+__END__
+
+=head1 NAME
+
+if - C<use> a Perl module if a condition holds
+
+=head1 SYNOPSIS
+
+  use if CONDITION, MODULE => ARGUMENTS;
+
+=head1 DESCRIPTION
+
+The construct
+
+  use if CONDITION, MODULE => ARGUMENTS;
+
+has no effect unless C<CONDITION> is true.  In this case the effect is
+the same as of
+
+  use MODULE ARGUMENTS;
+
+Above C<< => >> provides necessary quoting of C<MODULE>.  If not used (e.g.,
+no ARGUMENTS to give), you'd better quote C<MODULE> yourselves.
+
+=head1 BUGS
+
+The current implementation does not allow specification of the
+required version of the module.
+
+=head1 AUTHOR
+
+Ilya Zakharevich L<mailto:perl-module-if@ilyaz.org>.
+
+=cut
+
diff --git a/dist/if/t/if.t b/dist/if/t/if.t
new file mode 100644
index 0000000000..badab64f04
--- /dev/null
+++ b/dist/if/t/if.t
@@ -0,0 +1,37 @@
+#!./perl
+
+my $t = 1;
+print "1..5\n";
+sub ok {
+  print "not " unless shift;
+  print "ok $t # ", shift, "\n";
+  $t++;
+}
+
+my $v_plus = $] + 1;
+my $v_minus = $] - 1;
+
+unless (eval 'use open ":std"; 1') {
+  # pretend that open.pm is present
+  $INC{'open.pm'} = 'open.pm';
+  eval 'sub open::foo{}';		# Just in case...
+}
+
+
+ok( eval "use if ($v_minus > \$]), strict => 'subs'; \${'f'} = 12" eq 12,
+    '"use if" with a false condition, fake pragma');
+
+ok( eval "use if ($v_minus > \$]), strict => 'refs'; \${'f'} = 12" eq 12,
+    '"use if" with a false condition and a pragma');
+
+ok( eval "use if ($v_plus > \$]), strict => 'subs'; \${'f'} = 12" eq 12,
+    '"use if" with a true condition, fake pragma');
+
+ok( (not defined eval "use if ($v_plus > \$]), strict => 'refs'; \${'f'} = 12"
+     and $@ =~ /while "strict refs" in use/),
+    '"use if" with a true condition and a pragma');
+
+# Old version had problems with the module name `open', which is a keyword too
+# Use 'open' =>, since pre-5.6.0 could interpret differently
+ok( (eval "use if ($v_plus > \$]), 'open' => IN => ':crlf'; 12" || 0) eq 12,
+    '"use if" with open');