Fix bill numbers which could get the wrong year

coin/billing/models.py

@@ -87,7 +87,10 @@ class InvoiceNumber:
         :rtype: dict
         """
 
-        return {'{}__month'.format(field_name): date.month}
+        return {
+            '{}__month'.format(field_name): date.month,
+            '{}__year'.format(field_name): date.year
+        }
 
 
 class InvoiceQuerySet(models.QuerySet):

coin/billing/tests.py

@@ -328,6 +328,18 @@ class InvoiceQuerySetTests(TestCase):
             Invoice.objects.get_next_invoice_number(datetime.date(2016,1,1)),
             '2016-01-000002')
 
+    def test_get_right_year_invoice_number(self):
+        with freeze_time('2016-01-01'):
+            Invoice.objects.create(date=datetime.date(2016, 1, 1)).validate()
+        with freeze_time('2017-01-01'):
+            Invoice.objects.create(date=datetime.date(2017, 1, 1)).validate()
+        with freeze_time('2018-01-01'):
+            Invoice.objects.create(date=datetime.date(2018, 1, 1)).validate()
+
+        self.assertEqual(
+            Invoice.objects.get_next_invoice_number(datetime.date(2017, 1, 1)),
+            '2017-01-000002')
+
     def test_bill_date_is_validation_date(self):
         bill = Invoice.objects.create(date=datetime.date(2016,1,1))
         self.assertEqual(bill.date, datetime.date(2016,1,1))