From: Peter Rabbitson <ribasushi@cpan.org>
Date: Tue, 26 Oct 2010 11:16:26 +0000 (+0200)
Subject: Temporary fixes for 5.13.x $@ handling
X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=commitdiff_plain;h=1f870d5a08fa1794734380d7c8bd6753cdcf8f6d;p=dbsrgits%2FDBIx-Class-Historic.git

Temporary fixes for 5.13.x $@ handling

Some patchups to mitigate fallout from
http://perl5.git.perl.org/perl.git/commitdiff/96d9b9cd

Included several "time-bombs" set to go off when 5.13.8
is available (the "Contentious Changes freeze" release)
---

diff --git a/Changes b/Changes
index 4a609e2..a9ae59e 100644
--- a/Changes
+++ b/Changes
@@ -31,6 +31,8 @@ Revision history for DBIx::Class
 
     * Fixes
         - Fix memory leak during populate() on 5.8.x perls
+        - Temporarily fixed 5.13.x failures (RT#58225)
+          (perl-core fix still pending)
         - Fix result_soutrce_instance leaks on compose_namespace
         - Make sure exception_action does not allow exception-hiding
           due to badly-written handlers (the mechanism was never meant
diff --git a/lib/DBIx/Class/Storage/TxnScopeGuard.pm b/lib/DBIx/Class/Storage/TxnScopeGuard.pm
index f686cce..4365b9d 100644
--- a/lib/DBIx/Class/Storage/TxnScopeGuard.pm
+++ b/lib/DBIx/Class/Storage/TxnScopeGuard.pm
@@ -4,14 +4,69 @@ use strict;
 use warnings;
 use Carp::Clan qw/^DBIx::Class/;
 use Try::Tiny;
-use Scalar::Util qw/weaken/;
+use Scalar::Util qw/weaken blessed/;
+use DBIx::Class::Exception;
 use namespace::clean;
 
+# temporary until we fix the $@ issue in core
+# we also need a real appendable, stackable exception object
+# (coming soon)
+BEGIN {
+  if ($] < 5.013001) {
+    *IS_BROKEN_PERL = sub () { 0 };
+  }
+  elsif ($] < 5.013008) {
+    *IS_BROKEN_PERL = sub () { 1 };
+  }
+  else {
+    die 'The $@ debacle should have been resolved by now, adjust DBIC';
+  }
+}
+
+my ($guards_count, $compat_handler, $foreign_handler);
+
 sub new {
   my ($class, $storage) = @_;
 
   $storage->txn_begin;
   my $guard = bless [ 0, $storage, $storage->_dbh ], ref $class || $class;
+
+
+  # install a callback carefully
+  if (IS_BROKEN_PERL and !$guards_count) {
+
+    # if the thrown exception is a plain string, wrap it in our
+    # own exception class
+    # this is actually a pretty cool idea, may very well keep it
+    # after perl is fixed
+    $compat_handler ||= bless(
+      sub {
+        $@ = (blessed($_[0]) or ref($_[0]))
+          ? $_[0]
+          : bless ( { msg => $_[0] }, 'DBIx::Class::Exception')
+        ;
+        die;
+      },
+      '__TxnScopeGuard__FIXUP__',
+    );
+
+    if ($foreign_handler = $SIG{__DIE__}) {
+      $SIG{__DIE__} = bless (
+        sub {
+          # we trust the foreign handler to do whatever it wants, all we do is set $@
+          eval { $compat_handler->(@_) };
+          $foreign_handler->(@_);
+        },
+        '__TxnScopeGuard__FIXUP__',
+      );
+    }
+    else {
+      $SIG{__DIE__} = $compat_handler;
+    }
+  }
+
+  $guards_count++;
+
   weaken ($guard->[2]);
   $guard;
 }
@@ -26,6 +81,29 @@ sub commit {
 sub DESTROY {
   my ($dismiss, $storage) = @{$_[0]};
 
+  $guards_count--;
+
+  # don't touch unless it's ours, and there are no more of us left
+  if (
+    IS_BROKEN_PERL
+      and
+    !$guards_count
+  ) {
+
+    if (ref $SIG{__DIE__} eq '__TxnScopeGuard__FIXUP__') {
+      # restore what we saved
+      if ($foreign_handler) {
+        $SIG{__DIE__} = $foreign_handler;
+      }
+      else {
+        delete $SIG{__DIE__};
+      }
+    }
+
+    # make sure we do not leak the foreign one in case it exists
+    undef $foreign_handler;
+  }
+
   return if $dismiss;
 
   # if our dbh is not ours anymore, the weakref will go undef
@@ -47,7 +125,13 @@ sub DESTROY {
     catch { $rollback_exception = shift };
 
     if (defined $rollback_exception && $rollback_exception !~ /DBIx::Class::Storage::NESTED_ROLLBACK_EXCEPTION/) {
-      if ($exception) {
+      # append our text - THIS IS A TEMPORARY FIXUP!
+      # a real stackable exception object is in the works
+      if (ref $exception eq 'DBIx::Class::Exception') {
+        $exception->{msg} = "Transaction aborted: $exception->{msg} "
+          ."Rollback failed: ${rollback_exception}";
+      }
+      elsif ($exception) {
         $exception = "Transaction aborted: ${exception} "
           ."Rollback failed: ${rollback_exception}";
       }
@@ -62,7 +146,7 @@ sub DESTROY {
     }
   }
 
-  $@ = $exception;
+  $@ = $exception unless IS_BROKEN_PERL;
 }
 
 1;
diff --git a/t/52leaks.t b/t/52leaks.t
index 2f1867d..ad781ac 100644
--- a/t/52leaks.t
+++ b/t/52leaks.t
@@ -165,6 +165,10 @@ for my $slot (keys %$weak_registry) {
     delete $weak_registry->{$slot}
       unless $cleared->{hash_merge_singleton}{$weak_registry->{$slot}{weakref}{behavior}}++;
   }
+  elsif ($slot =~ /^__TxnScopeGuard__FIXUP__/) {
+    die 'The $@ debacle should have been fixed by now!!!' if $] >= 5.013008;
+    delete $weak_registry->{$slot};
+  }
 }
 
 
diff --git a/xt/podcoverage.t b/xt/podcoverage.t
index 8c9132e..ba30f31 100644
--- a/xt/podcoverage.t
+++ b/xt/podcoverage.t
@@ -47,6 +47,11 @@ my $exceptions = {
             MULTICREATE_DEBUG
         /],
     },
+    'DBIx::Class::Storage::TxnScopeGuard' => {
+        ignore => [qw/
+            IS_BROKEN_PERL
+        /],
+    },
     'DBIx::Class::FilterColumn' => {
         ignore => [qw/
             new