Fixed #2443 -- Added DurationField.

A field for storing periods of time - modeled in Python by timedelta. It
is stored in the native interval data type on PostgreSQL and as a bigint
of microseconds on other backends.

Also includes significant changes to the internals of time related maths
in expressions, including the removal of DateModifierNode.

Thanks to Tim and Josh in particular for reviews.

2 files changed, 71 insertions, 0 deletions

diff --git a/tests/model_fields/models.py b/tests/model_fields/models.py
index bb75208905..e9e287f04f 100644
--- a/tests/model_fields/models.py
+++ b/tests/model_fields/models.py
@@ -121,6 +121,10 @@ class DateTimeModel(models.Model):
     t = models.TimeField()
 
 
+class DurationModel(models.Model):
+    field = models.DurationField()
+
+
 class PrimaryKeyCharModel(models.Model):
     string = models.CharField(max_length=10, primary_key=True)
 
diff --git a/tests/model_fields/test_durationfield.py b/tests/model_fields/test_durationfield.py
new file mode 100644
index 0000000000..fc2c22af61
--- /dev/null
+++ b/tests/model_fields/test_durationfield.py
@@ -0,0 +1,67 @@
+import datetime
+import json
+
+from django.core import exceptions, serializers
+from django.db import models
+from django.test import TestCase
+
+from .models import DurationModel
+
+
+class TestSaveLoad(TestCase):
+
+    def test_simple_roundtrip(self):
+        duration = datetime.timedelta(days=123, seconds=123, microseconds=123)
+        DurationModel.objects.create(field=duration)
+        loaded = DurationModel.objects.get()
+        self.assertEqual(loaded.field, duration)
+
+
+class TestQuerying(TestCase):
+
+    @classmethod
+    def setUpTestData(cls):
+        cls.objs = [
+            DurationModel.objects.create(field=datetime.timedelta(days=1)),
+            DurationModel.objects.create(field=datetime.timedelta(seconds=1)),
+            DurationModel.objects.create(field=datetime.timedelta(seconds=-1)),
+        ]
+
+    def test_exact(self):
+        self.assertSequenceEqual(
+            DurationModel.objects.filter(field=datetime.timedelta(days=1)),
+            [self.objs[0]]
+        )
+
+    def test_gt(self):
+        self.assertSequenceEqual(
+            DurationModel.objects.filter(field__gt=datetime.timedelta(days=0)),
+            [self.objs[0], self.objs[1]]
+        )
+
+
+class TestSerialization(TestCase):
+    test_data = '[{"fields": {"field": "1 01:00:00"}, "model": "model_fields.durationmodel", "pk": null}]'
+
+    def test_dumping(self):
+        instance = DurationModel(field=datetime.timedelta(days=1, hours=1))
+        data = serializers.serialize('json', [instance])
+        self.assertEqual(json.loads(data), json.loads(self.test_data))
+
+    def test_loading(self):
+        instance = list(serializers.deserialize('json', self.test_data))[0].object
+        self.assertEqual(instance.field, datetime.timedelta(days=1, hours=1))
+
+
+class TestValidation(TestCase):
+
+    def test_invalid_string(self):
+        field = models.DurationField()
+        with self.assertRaises(exceptions.ValidationError) as cm:
+            field.clean('not a datetime', None)
+        self.assertEqual(cm.exception.code, 'invalid')
+        self.assertEqual(
+            cm.exception.message % cm.exception.params,
+            "'not a datetime' value has an invalid format. "
+            "It must be in [DD] [HH:[MM:]]ss[.uuuuuu] format."
+        )