[Dbix-class] Patch and test for DBIx::Class storage->connected() bug

[luke saunders]

There is a bug in method connected of DBIx::Class::Storage::DBI: it
doesn't check that $dbh is still valid after it has called
$self->_verify_pid. _verify_pid() will invalidate $dbh if the connection
has been created in a different process (the parent).

Here is a patch with a potential fix and a test case for this problem.

Index: t/50fork.t
===================================================================
--- t/50fork.t  (revision 3641)
+++ t/50fork.t  (working copy)
@@ -18,7 +18,7 @@
    $num_children = 10;
 }

-plan tests => $num_children + 5;
+plan tests => $num_children + 6;

 use lib qw(t/lib);

@@ -45,6 +45,23 @@
 };
 ok(!$@) or diag "Creation eval failed: $@";

+{
+    my $pid = fork;
+    if(!defined $pid) {
+        die "fork failed: $!";
+    }
+
+    if (!$pid) {
+        exit $schema->storage->connected ? 1 : 0;
+    }
+
+    if (waitpid($pid, 0) == $pid) {
+        my $ex = $? >> 8;
+        ok($ex == 0, "storage->connected() returns false in child");
+        exit $ex if $ex; # skip remaining tests
+    }
+}
+
 my @pids;
 while(@pids < $num_children) {

Index: lib/DBIx/Class/Storage/DBI.pm
===================================================================
--- lib/DBIx/Class/Storage/DBI.pm       (revision 3641)
+++ lib/DBIx/Class/Storage/DBI.pm       (working copy)
@@ -665,6 +665,7 @@
       }
       else {
           $self->_verify_pid;
+          return 0 if !$self->_dbh;
       }
       return ($dbh->FETCH('Active') && $dbh->ping);
   }