decimal values passed as string now work (again)

oscar/templatetags/currency_filters.py

@@ -1,3 +1,5 @@
+from decimal import InvalidOperation, Decimal as D
+
 from django import template
 from django.conf import settings
 from babel.numbers import format_currency
@@ -18,4 +20,10 @@ def currency(value):
     locale = getattr(settings, 'OSCAR_CURRENCY_LOCALE', None)
     if locale:
         kwargs['locale'] = locale
+
+    try:
+        value = D(value)
+    except (TypeError, InvalidOperation):
+        return u""
+
     return format_currency(value, **kwargs)

tests/unit/currency_filters_tests.py

@@ -0,0 +1,31 @@
+from decimal import Decimal as D
+
+from django.conf import settings
+from django.test import TestCase
+
+from oscar.templatetags.currency_filters import currency
+
+
+class TestCurrencyFilter(TestCase):
+
+    def test_formats_a_decimal_value_using_oscar_setting(self):
+        default = settings.OSCAR_DEFAULT_CURRENCY
+        settings.OSCAR_DEFAULT_CURRENCY = u'USD'
+
+        formatted = currency(D('23.54'))
+        self.assertEquals(formatted, u'US$23.54')
+
+        # rest to default for further testing
+        settings.OSCAR_DEFAULT_CURRENCY = default
+
+    def test_formats_a_decimal_value_using_oscar_default_setting(self):
+        formatted = currency(D('23.54'))
+        self.assertEquals(formatted, u'£23.54')
+
+    def test_formats_a_string_value_using_oscar_default_setting(self):
+        formatted = currency('23.54')
+        self.assertEquals(formatted, u'£23.54')
+
+    def test_formats_empty_string_as_empty_value(self):
+        formatted = currency('')
+        self.assertEquals(formatted, u'')