Improve default= handling on MoneyField

django_prices/models.py

@@ -15,6 +15,11 @@ class MoneyField(models.DecimalField):
 
     def __init__(self, verbose_name=None, currency=None, **kwargs):
         self.currency = currency
+        if (isinstance(kwargs.get('default'), Money) and
+                kwargs['default'].currency != self.currency):
+            raise ValueError(
+                'Invalid currency for default value: %r (expected %r)' % (
+                    kwargs['default'].currency, self.currency))
         super(MoneyField, self).__init__(verbose_name, **kwargs)
 
     def from_db_value(self, value, expression, connection, context):
@@ -67,6 +72,8 @@ def validators(self):
     def deconstruct(self):
         name, path, args, kwargs = super(MoneyField, self).deconstruct()
         kwargs['currency'] = self.currency
+        if isinstance(kwargs.get('default'), Money):
+            kwargs['default'] = kwargs['default'].amount
         return name, path, args, kwargs
 
 

tests/models.py

@@ -1,5 +1,6 @@
 from django.db import models
 from django_prices.models import MoneyField, TaxedMoneyField
+from prices import Money
 
 
 class Model(models.Model):
@@ -10,3 +11,9 @@ class Model(models.Model):
         'gross', currency='BTC', default='5', max_digits=9,
         decimal_places=2)
     price = TaxedMoneyField(net_field='price_net', gross_field='price_gross')
+
+
+class ModelWithDefault(models.Model):
+    price = MoneyField(
+        currency='USD', default=Money('0', 'USD'), max_digits=9,
+        decimal_places=2)

tests/test_prices.py

@@ -6,7 +6,7 @@
 
 import pytest
 from django.core.exceptions import ValidationError
-from django.db import connection
+from django.db import connection, models
 from django.utils import translation
 from prices import Money, TaxedMoney, percentage_discount
 
@@ -19,7 +19,7 @@
 
 from .forms import (
     ModelForm, OptionalPriceForm, RequiredPriceForm, ValidatedPriceForm)
-from .models import Model
+from .models import Model, ModelWithDefault
 
 
 @pytest.fixture(scope='module')
@@ -197,6 +197,27 @@ def test_combined_field_validation():
         instance.full_clean()
 
 
+def test_money_field_default_money():
+    instance = ModelWithDefault()
+    assert instance.price == Money(0, 'USD')
+
+
+def test_money_field_default_money_deconstruct():
+    instance = ModelWithDefault()
+    _, _, _, kwargs = instance._meta.get_field('price').deconstruct()
+    assert kwargs == {
+        'currency': 'USD', 'default': Decimal(0), 'max_digits': 9,
+        'decimal_places': 2}
+
+
+def test_money_field_default_money_invalid_currency():
+    with pytest.raises(ValueError):
+        class InvalidModel(models.Model):
+            price = MoneyField(
+                currency='USD', default=Money('0', 'BTC'), max_digits=9,
+                decimal_places=2)
+
+
 def test_field_passes_all_validations():
     form = RequiredPriceForm(data={'price_net': '20'})
     form.full_clean()