Bug 18731: Overload K::A::Fund->to_api to avoid conflict

This patch overloads the to_api methods on the Fund class, so
conflicting (on mapping) attribute names are not a problem.

To test:
1. Apply this patch
2. Run:
   $ kshell
  k$ prove t/db_dependent/Koha/Acquisition/Fund.t \
           t/db_dependent/Koha/REST/Plugin/Objects.t
=> SUCCESS: Tests pass!
3. Sign off :-D

Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>

Koha/Acquisition/Fund.pm

@@ -29,6 +29,29 @@ Koha::Acquisition::Fund object class
 
 =head2 Class methods
 
+=head3 to_api
+
+    my $json = $fund->to_api;
+
+Overloaded method that returns a JSON representation of the Koha::Acquisition::Fund object,
+suitable for API output.
+
+=cut
+
+sub to_api {
+    my ( $self, $args ) = @_;
+
+    # Preserve conflicting attribute names
+    my $budget_id        = $self->budget_id;
+    my $budget_period_id = $self->budget_period_id;
+
+    my $json_fund = $self->SUPER::to_api($args);
+    $json_fund->{fund_id}   = $budget_id;
+    $json_fund->{budget_id} = $budget_period_id;
+
+    return $json_fund;
+}
+
 =head3 to_api_mapping
 
 This method returns the mapping for representing a Koha::Acquisition::Fund object

t/db_dependent/Koha/Acquisition/Fund.t

@@ -0,0 +1,44 @@
+#!/usr/bin/perl
+
+# Copyright 2019 Koha Development team
+#
+# 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 Test::More tests => 1;
+
+use t::lib::TestBuilder;
+
+use Koha::Database;
+
+my $schema  = Koha::Database->schema;
+my $builder = t::lib::TestBuilder->new;
+
+subtest 'to_api() tests' => sub {
+
+    plan tests => 2;
+
+    $schema->storage->txn_begin;
+
+    my $fund = $builder->build_object({ class => 'Koha::Acquisition::Funds' });
+    my $fund_api = $fund->to_api();
+
+    is( $fund->budget_id, $fund_api->{fund_id}, 'Mapping is correct for budget_id' );
+    is( $fund->budget_period_id, $fund_api->{budget_id}, 'Mapping is correct for budget_period_id' );
+
+    $schema->storage->txn_rollback;
+};