over*: avoid defined-or hash assignments with side-effects

These may've been causing strange errors[1] in t/imapd.t from
the -watch daemon, such as:

	Cannot copy to HASH in scalar assignment ../PublicInbox/Over.pm

in the Over->dbh() sub.  I've only noticed this failure on
FreeBSD 13.2 (Perl 5.32.1, DBD::SQLite 1.72 (bundled SQLite
3.39.4), DBI 1.643) so far, so it could also be something to do
with the versions used and/or memory layout differences
with libc or build toolchain.

1 files changed, 11 insertions, 2 deletions

diff --git a/lib/PublicInbox/Over.pm b/lib/PublicInbox/Over.pm
index e3a8adb1..4eed4f46 100644
--- a/lib/PublicInbox/Over.pm
+++ b/lib/PublicInbox/Over.pm
@@ -82,7 +82,13 @@ sub dbh_close {
         }
 }
 
-sub dbh ($) { $_[0]->{dbh} //= $_[0]->dbh_new } # dbh_new may be subclassed
+sub dbh ($) {
+        my ($self) = @_;
+        $self->{dbh} // do {
+                my $dbh = $self->dbh_new; # dbh_new may be subclassed
+                $self->{dbh} = $dbh;
+        }
+}
 
 sub load_from_row ($;$) {
         my ($smsg, $cull) = @_;
@@ -256,9 +262,12 @@ SELECT ts,ds,ddd FROM over WHERE $s
 sub get_art {
         my ($self, $num) = @_;
         # caching $sth ourselves is faster than prepare_cached
-        my $sth = $self->{-get_art} //= dbh($self)->prepare(<<'');
+        my $sth = $self->{-get_art} // do {
+                my $sth = dbh($self)->prepare(<<'');
 SELECT num,tid,ds,ts,ddd FROM over WHERE num = ? LIMIT 1
 
+                $self->{-get_art} = $sth;
+        };
         $sth->execute($num);
         my $smsg = $sth->fetchrow_hashref;
         $smsg ? load_from_row($smsg) : undef;