File::stat: always return a scalar, even in list context

Previously, a failing stat would return an empty list in list context,
not undef. This can cause surprises in code like:

    foo(stat $file);  # would call foo() without arguments if stat fails

    my %hash = (
        stat => stat($file),
        # Odd number of elements in hash assignment if stat fails
    );

Author: mauke

lib/File/stat.pm

@@ -185,7 +185,7 @@ struct 'File::stat' => [
 ];
 
 sub populate {
-    return unless @_;
+    return undef unless @_;
     my $stob = new();
     @$stob = (
 	$st_dev, $st_ino, $st_mode, $st_nlink, $st_uid, $st_gid, $st_rdev,
@@ -199,16 +199,15 @@ sub lstat :prototype($) { populate(CORE::lstat(shift)) }
 sub stat :prototype($) {
     my $arg = shift;
     my $st = populate(CORE::stat $arg);
-    return $st if defined $st;
-    return if ref $arg;
+    return $st if defined $st || ref $arg;
     # ... maybe $arg is the name of a bareword handle?
     my $fh;
     {
         local $!;
         no strict 'refs';
         require Symbol;
         $fh = \*{ Symbol::qualify( $arg, caller() )};
-        return unless defined fileno $fh;
+        return undef unless defined fileno $fh;
     }
     return populate(CORE::stat $fh);
 }

lib/File/stat.t

@@ -225,6 +225,18 @@ SKIP:
     is stat({}), undef, 'stat({}) fails by returning undef';
 }
 
+{
+    # list context
+
+    my @ret = stat '/ no such file';
+    is scalar(@ret), 1, 'stat returns one value in list context on failure';
+    is $ret[0], undef, 'stat returns undef on failure';
+
+    @ret = stat $file;
+    is scalar(@ret), 1, 'stat returns one value in list context on success';
+    isa_ok $ret[0], 'File::stat', 'successful stat in list context';
+}
+
 # Testing pretty much anything else is unportable.
 
 done_testing;