Perl: Force stacktrace for "can't call method on undefined"
exception, perl
Solution
I am not sure if it works within Catalyst, but usually you can force a stacktrace by including the CPAN module `Carp::Always`, e.g. by writing somewhere in your program `use Carp::Always;` or starting the perl script with the `-MCarp::Always` switch.
Problem
I'm using Perl and Catalyst as Web-Framework. How can I globally force a stacktrace if an exception like `Can't call method "XXX" on an undefined value...` is thrown? Suppose the following code in your `Controller/Root.pm` ``` use DateTime; sub test :Local :Args(0) { my ( $self, $c ) = @_; my $now = DateTime->now(time_zone=>'local'); my $tmp = undef; my $throwing = $tmp - $now; #this will throw an exception! $c->res->body("OK"); } ``` Opening `http://localhost:3000/test` throws of course the exception: Caught exception in MyApp::Controller::Root->test "Can't call method "subtract_datetime" on an undefined value at /usr/local/lib/perl/5.10.1/DateTime.pm line 1619, line 1003." The stacktrace is missing! How can I force in such a case a stacktrace? I.e. I would like to get (not a real output, only composed by hand): ``` MyApp::Controller::Root::__ANON__('Can\'t call method "subtract_datetime" on an undefined value at /usr/local/lib/perl/5.10.1/DateTime.pm line 1619, <DATA> line 1003.^J') called at /home/user/MyApp/script/../lib/MyApp/Controller/Root.pm line 114 MyApp::Controller::Root::test('MyApp::Controller::Root=HASH(0x20583b60)', 'MyApp=HASH(0x206e9140)') called at /usr/local/share/perl/5.10.1/Catalyst/Action.pm line 65 Catalyst::Action::execute('Catalyst::Action=HASH(0x20668e88)', 'MyApp::Controller::Root=HASH(0x20583b60)', 'MyApp=HASH(0x206e9140)') called at /usr/local/share/perl/5.10.1/Catalyst.pm line 1687 eval {...} at /usr/local/share/perl/5.10.1/Catalyst.pm line 1687 Catalyst::execute('MyApp=HASH(0x206e9140)', 'MyApp::Controller::Root', 'Catalyst::Action=HASH(0x20668e88)') called at /usr/local/share/perl/5.10.1/Catalyst/Action.pm line 60 [ and the rest of the exception ...] ``` With this I know exactly that the exception was caused by the line 114 in Root.pm