fix issue where dbh errcode gets lost when transaction fails to start

Author: Grinnz

Changes

@@ -1,5 +1,6 @@
 {{$NEXT}}
   - wal_mode is now off by default, but can be enabled with the wal_mode option.
+  - Fix issue where a transaction that failed to begin would rollback and clear the database handle error.
 
 3.009     2022-03-22 20:16:03 EDT
   - Fix race condition in Mojo::SQLite::Migrations where two processes could attempt to create the same migration. (#25, Oliver Kurz)

lib/Mojo/SQLite/Transaction.pm

@@ -10,14 +10,15 @@ has db => undef, weak => 1;
 my %behaviors = map { ($_ => 1) } qw(deferred immediate exclusive);
 
 sub new {
-  my $self = shift->SUPER::new(@_, rollback => 1);
+  my $self = shift->SUPER::new(@_);
   my $dbh = $self->{dbh} = $self->db->dbh;
   if (my $behavior = $self->{behavior}) {
     croak qq{Invalid transaction behavior $behavior} unless exists $behaviors{lc $behavior};
     $dbh->do("begin $behavior transaction");
   } else {
     $dbh->begin_work;
   }
+  $self->{rollback} = 1;
   return $self;
 }
 

t/results.t

@@ -148,6 +148,18 @@ my $sql = Mojo::SQLite->new;
     like $@, qr/does_not_exist/, 'right error';
     is_deeply $db->query('select * from results_test where name = ?', 'tx3')
       ->hashes->to_array, [], 'no results';
+    {
+      my $timeout = $db->dbh->sqlite_busy_timeout // 0;
+      $db->dbh->sqlite_busy_timeout(100);
+      my $tx;
+      eval {
+        $tx = $db->begin('immediate');
+        $db->begin('immediate');
+      };
+      ok $@, 'transaction failed';
+      ok $db->dbh->err, 'database error code retained';
+      $db->dbh->sqlite_busy_timeout($timeout);
+    }
   };
 
   subtest 'Issue #2' => sub {