DateTimeRangeField.value_to_string raises TypeError

[Villiers Strauss]

DateTimeRangeField's value_to_string method raises TypeError because json.dumps is unable to serialize datetime.datetime objects.

Steps to replicate:

Step 1:

# myapp/models.py
from django.contrib.postgres.fields import DateTimeRangeField
from django.db.models import Model

class DateTimeRangeTest(Model):
    date_time_range = DateTimeRangeField()

Step 2: migrate etc.

Step 3:

from django.contrib.postgres.fields import DateTimeRangeField
from myapp.models import DateTimeRangeTest

t = DateTimeRangeTest.objects.create(date_time_range=('2015-06-05 16:00:00+0200','2015-06-05 17:00:00+0200'))

dtrf = DateTimeRangeField()
dtrf.attname = 'date_time_range'
dtrf.value_to_string(t)  
# raises: TypeError: datetime.datetime(2015, 6, 5, 14, 00, 00, tzinfo=<UTC>) is not JSON serializable

---

The value_to_string method is used with the manage.py dumpdata command, so this bug effectively breaks dumpdata for models with DateTimeRangeFields.

[Claude Paroz]

DateField is serializing its value through isoformat(), so I guess date-based range fields should do something similar.

[Matthew Somerville]

I'll add a test to show this, and hopefully a patch.

[Matthew Somerville]

PR at ​https://github.com/django/django/pull/4818 – I used DjangoJSONEncoder on the base value_to_string so that it should hopefully handle both DateRangeField and DateTimeRangeField (the changed test did fail on both those ranges). The PR does pass, the failure is in the last commit on master, I'm afraid :)

[Matthew Somerville <matthew-github@…>]

In 2926559c:

Fixed #24937 -- fix serialization of Date(Time)RangeField.

Use the DjangoJSONEncoder so that datetime and date are encoded
appropriately.

[Marc Tamlyn <marc.tamlyn@…>]

In d58816b:

Merge pull request #4818 from dracos/24937-ranging-to-victory

Fixed #24937 -- fix serialization of Date(Time)RangeField.

[Tim Graham <timograham@…>]

In 3ded51bc:

[1.8.x] Fixed #24937 -- Fixed serialization of Date(Time)RangeField.

Use the DjangoJSONEncoder so that datetime and date are encoded
appropriately.

Backport of 2926559cce34e48efb4b073721926d737e372dd3 from master

[Tim Graham <timograham@…>]

In 34bb6c0:

Refs #24937 -- Forwardport of 1.8.7 release note.

Forwardport of 3ded51bcf21f384b2e80ce97aff5c12d63e5f0e3 from stable/1.8.x

[Tim Graham <timograham@…>]

In 5bb40e7:

[1.9.x] Refs #24937 -- Forwardport of 1.8.7 release note.

Forwardport of 3ded51bcf21f384b2e80ce97aff5c12d63e5f0e3 from stable/1.8.x

[Tim Graham <timograham@…>]

In 2c96b3d:

[1.8.x] Refs #24937 -- Backported more commits to fix for serialization of Date(Time)RangeField.

Instead of using DjangoJSONEncoder, use base_field's value_to_string().

Note this means the serialization of e.g. IntegerRangeField now has
strings for lower and upper, so use to_python when they came back in
(same behaviour as ArrayField, hopefully, from where I also got the
set_attributes_from_name function).

Backport of 86d9b10dc33cc115fee2ecab40a569354ac55d15 and
8a842148b6deaab021526e2689279cf5e232945f from master