support :void to enable croaking only in void context (from

Simon Cozens <simon@othersideofthe.earth.li>)

p4raw-id: //depot/perl@5600

1 files changed, 37 insertions, 10 deletions

diff --git a/lib/Fatal.pm b/lib/Fatal.pm
index d033d62713..1496117c89 100644
--- a/lib/Fatal.pm
+++ b/lib/Fatal.pm
@@ -12,9 +12,15 @@ $Debug = 0 unless defined $Debug;
 sub import {
     my $self = shift(@_);
     my($sym, $pkg);
+    my $void = 0;
     $pkg = (caller)[0];
     foreach $sym (@_) {
-	&_make_fatal($sym, $pkg);
+	if ($sym eq ":void") {
+	    $void = 1;
+	}
+	else {
+	    &_make_fatal($sym, $pkg, $void);
+	}
     }
 };
 
@@ -42,11 +48,11 @@ sub fill_protos {
 }
 
 sub write_invocation {
-  my ($core, $call, $name, @argvs) = @_;
+  my ($core, $call, $name, $void, @argvs) = @_;
   if (@argvs == 1) {		# No optional arguments
     my @argv = @{$argvs[0]};
     shift @argv;
-    return "\t" . one_invocation($core, $call, $name, @argv) . ";\n";
+    return "\t" . one_invocation($core, $call, $name, $void, @argv) . ";\n";
   } else {
     my $else = "\t";
     my (@out, @argv, $n);
@@ -56,7 +62,7 @@ sub write_invocation {
       push @out, "$ {else}if (\@_ == $n) {\n";
       $else = "\t} els";
       push @out, 
-          "\t\treturn " . one_invocation($core, $call, $name, @argv) . ";\n";
+          "\t\treturn " . one_invocation($core, $call, $name, $void, @argv) . ";\n";
     }
     push @out, <<EOC;
 	}
@@ -67,21 +73,27 @@ EOC
 }
 
 sub one_invocation {
-  my ($core, $call, $name, @argv) = @_;
+  my ($core, $call, $name, $void, @argv) = @_;
   local $" = ', ';
-  return qq{$call(@argv) || croak "Can't $name(\@_)} . 
-    ($core ? ': $!' : ', \$! is \"$!\"') . '"';
+  if ($void) { 
+    return qq/(defined wantarray)?$call(@argv):
+              $call(@argv) || croak "Can't $name(\@_)/ . 
+           ($core ? ': $!' : ', \$! is \"$!\"') . '"'
+  } else {
+    return qq{$call(@argv) || croak "Can't $name(\@_)} . 
+           ($core ? ': $!' : ', \$! is \"$!\"') . '"';
+  }
 }
 
 sub _make_fatal {
-    my($sub, $pkg) = @_;
+    my($sub, $pkg, $void) = @_;
     my($name, $code, $sref, $real_proto, $proto, $core, $call);
     my $ini = $sub;
 
     $sub = "${pkg}::$sub" unless $sub =~ /::/;
     $name = $sub;
     $name =~ s/.*::// or $name =~ s/^&//;
-    print "# _make_fatal: sub=$sub pkg=$pkg name=$name\n" if $Debug;
+    print "# _make_fatal: sub=$sub pkg=$pkg name=$name void=$void\n" if $Debug;
     croak "Bad subroutine name for Fatal: $name" unless $name =~ /^\w+$/;
     if (defined(&$sub)) {	# user subroutine
 	$sref = \&$sub;
@@ -109,7 +121,7 @@ sub$real_proto {
 	local(\$", \$!) = (', ', 0);
 EOS
     my @protos = fill_protos($proto);
-    $code .= write_invocation($core, $call, $name, @protos);
+    $code .= write_invocation($core, $call, $name, $void, @protos);
     $code .= "}\n";
     print $code if $Debug;
     {
@@ -150,6 +162,21 @@ replaced.  You may wrap both user-defined functions and overridable
 CORE operators (except C<exec>, C<system> which cannot be expressed
 via prototypes) in this way.
 
+If the symbol C<:void> appears in the import list, then functions
+named later in that import list raise an exception only when
+these are called in void context--that is, when their return
+values are ignored.  For example
+
+	use Fatal qw/:void open close/;
+
+	# properly checked, so no exception raised on error
+	if(open(FH, "< /bogotic") {
+		warn "bogo file, dude: $!";
+	}
+
+	# not checked, so error raises an exception
+	close FH;
+
 =head1 AUTHOR
 
 Lionel.Cons@cern.ch