Replace timezone code by Django's built in solution

[anapaulagomes]

Model Bakery has a module to deal with timezones that was implemented before Django had a built in support for it. We should replace it by the timezone API from Django 1.11.

https://github.com/model-bakers/model_bakery/blob/c2b609f6b065e587cf4a2e4253b518634d4995b3/model_bakery/timezone.py

Expected behavior

This lib should use Django's built in timezone library instead of bakery's timezone module.

Things I could think of:

• Replace calls to smart_datetime
• Replace calls to tz_aware
• Replace calls to now
• Replace calls to utc
• Delete bakery's timezone module

[dubesar]

@anapaulagomes By delete timezone module you mean to delete timezone.py?

[anapaulagomes]

Yes, @dubesar. I just updated the text to make it more explicit.

[dubesar]

@anapaulagomes So basically all the imports of timezone.py in all the other modules have to be replaced and also a single line of django for timezone is to be included.

[anapaulagomes]

I can't tell for sure that these are the only things needed here. Yes, this issue is mainly about replacing the methods from model_bakery/timezone.py by Django's timezone module. But we have to make sure that the library still works the same way as before having the module replaced, which may include to adapt some things. @dubesar

[dubesar]

@anapaulagomes what I am thinking to do is :
1.
Replace :

from datetime import datetime

try:
    from django.conf import settings
    from django.utils.timezone import now, utc
except ImportError:
    def now():
        return datetime.now()

with

from django.utils import timezone
import datetime

def now():
    """
    Returns an aware or naive datetime.datetime, depending on settings.USE_TZ.
    """
    if settings.USE_TZ:
        # timeit shows that datetime.now(tz=utc) is 24% slower
        return datetime.utcnow().replace(tzinfo=utc)
    else:
        return datetime.now()

Remove tz_aware as now is sufficient and also remove smart_datetime

Replace :

model_bakery/model_bakery/utils.py

Line 44 in c2b609f

series_date = tz_aware(datetime.datetime.utcfromtimestamp(start + n))

with

series_date = now()+n

And there seems to be no change in random_gen.py

[dubesar]

@anapaulagomes If you find these changes correct then ping me so that I can make changes in the repo

[anapaulagomes]

A good way of starting this is making all the changes needed in model_bakery/timezone.py and expect the tests to pass. After calling Django's methods from bakery's methods and making sure that everything is working fine, you'll be fine to replace the calls all over the code base. @dubesar

For the example you've shown, I'd say that just from django.utils.timezone import now would be enough. From Django's docs:

When time zone support is enabled (USE_TZ=True), Django uses time-zone-aware datetime objects. If your code creates datetime objects, they should be aware too. In this mode, the example above becomes:
from django.utils import timezone
now = timezone.now()

To test now()'s case you only need to remove its try/except and then run the tests. This try/except was there to make sure that a code from before Django 1.4 would work. So now instead of returning datetime.now() we'd be just importing Django's method there.

From:

try:
    from django.conf import settings
    from django.utils.timezone import now, utc
except ImportError:
    def now():
        return datetime.now()

To:

from django.conf import settings
from django.utils.timezone import now, utc

Same goes to tz_aware and smart_datetime. Please make sure tests are passing. :)

Any thoughts here, @amureki?

[amureki]

Done in:
#141
#143
#147

Please, note, I left model_bakery.timezone. tz_aware - I think, this is good to have. However, I am happy to reopen this if anyone would be having suggestions.