Bug 25032: Generic unhandled exception handling on API

This patch adds Koha::Logger as the default logger for the API, and
introduces a new helper plugin that takes care of handling the unhandled
exceptions. Basically, with this we would write something like this in
our controller methods:

    try {
        ...
    }
    catch {
        if ( know_exception ) {
            handle_known_exception($_);
        }

        $c->unhandled_exception($_);
    }

Without this, we end up adding more and more handling 'just in case'.

To test:
1. Edit the Koha/REST/V1/Cities.pm 'list' method adding
   die("Nada"); before the render step.
2. Restart plack and try the endpoint
=> FAIL: A generic error is displayed, and no traces of the original
problem are found on the logs.
3. Apply this patches, make sure your instance's log4perl has the
   introduced lines for API with the right path.
4. Repeat 2
=> SUCCESS: The message is still generic, but you see something is
logged in /var/log/koha/kohadev/api-error.log
5. Change die("Nada"); for a real exception like:

    use Koha::Exceptions;
    Koha::Exceptions::DuplicateObject->throw("Nada");
6. Repeat 2.
=> SUCCESS: The message is generic, but a meaningful text is added to
the logs.

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>

Koha/REST/Plugin/Exceptions.pm

@@ -0,0 +1,83 @@
+package Koha::REST::Plugin::Exceptions;
+
+# This file is part of Koha.
+#
+# Koha is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# Koha is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Koha; if not, see <http://www.gnu.org/licenses>.
+
+use Modern::Perl;
+
+use Scalar::Util qw( blessed );
+use Koha::Logger;
+
+use Mojo::Base 'Mojolicious::Plugin';
+
+=head1 NAME
+
+Koha::REST::Plugin::Exceptions
+
+=head1 API
+
+=head2 Helper methods
+
+=head3 unhandled_exception
+
+    try {
+        ...
+    }
+    catch {
+        if ( know_exception ) {
+            handle_known_exception($_);
+        }
+
+        $c->unhandled_exception($_);
+    }
+
+Provides a generic and reusable way to throw unhandled exceptions. This way we
+can centralize the behaviour control (e.g. production vs. development environmet)
+
+=cut
+
+sub register {
+    my ( $self, $app ) = @_;
+
+    $app->helper(
+        'unhandled_exception' => sub {
+            my ( $c, $exception ) = @_;
+
+            my $req    = $c->req;
+            my $method = $req->method;
+            my $path   = $req->url->to_abs->path;
+            my $type = "";
+
+            if ( blessed $exception ) {
+                $type = "(" . ref($exception) . ")";
+            }
+
+            my $message = "$method $path: unhandled exception $type\<\<$exception\>\>";
+
+            $c->app->log->error("$message");
+
+            $c->render(
+                status  => 500,
+                openapi => {
+                    error =>
+                      "Something went wrong, check Koha logs for details."
+                }
+            );
+          }
+
+    );
+}
+
+1;

Koha/REST/V1.pm

@@ -40,6 +40,8 @@ Overloaded Mojolicious->startup method. It is called at application startup.
 sub startup {
     my $self = shift;
 
+    $self->log( Koha::Logger->get({ interface => 'api' }) );
+
     $self->hook(
         before_dispatch => sub {
             my $c = shift;
@@ -132,6 +134,7 @@ sub startup {
     $self->plugin( 'Koha::REST::Plugin::Pagination' );
     $self->plugin( 'Koha::REST::Plugin::Query' );
     $self->plugin( 'Koha::REST::Plugin::Objects' );
+    $self->plugin( 'Koha::REST::Plugin::Exceptions' );
 }
 
 1;