Linters for some common issues we encounter.- flake8-iw
Run command to build wheel and tarball.
python3 -m build
twine check --strict dist/*
twine upload dist/*
Run command to test.
pytest
To run package in edit mode (to test on live code) from the directory where running flake8. This requires pip >= 21.3.1.
pip install -e ../flake8_iw/
Lint check to prevent the use of patch directly.
Recommendation: Use PatchingTestCase / PatchingTransactionTestCase instead
Correct ✅
from instawork.tests import PatchingTestCase
class SignUpUpdatedTests(PatchingTestCase):
def setUp(self):
self.mock_call = self.patch("apps.auth.signals.task_send_email.delay")
def test_email(self):
expect(self.mock_call).to(have_been_called_once)
def test_sms(self):
mock_sms = self.patch("apps.auth.signals.task_send_sms.delay")
expect(mock_sms).to(have_been_called_once)
Wrong ⚠️
from unittest.mock import patch
class SignUpUpdatedTests(TestCase):
def setUp(self):
self.patcher = patch("apps.auth.signals.task_send_email.delay")
self.mock_email = self.patcher.start()
def tearDown(self):
self.patcher.stop()
def test_email(self):
...
expect(self.mock_email).to(have_been_called_once)
@patch("apps.auth.signals.task_send_sms.delay")
def test_sms(self, mock_sms):
...
expect(mock_sms).to(have_been_called_once)
Lint check to prevent the use of patch to freeze time.
Recommendation: Use freeze_time from PatchingTestCase / PatchingTransactionTestCase or use freeze_time decorator or context manager from freezegun package.
Correct ✅
from django.utils import timezone
from instawork.tests import PatchingTestCase
class UserFeatureViewTests(PatchingTestCase):
def setUp(self):
self.now = timezone.now()
def test_feature_view(self):
ufv = None
# Option 1
with freeze_time(self.now):
ufv = UserFeatureView.objects.get_or_create(
user=self.shift.worker, feature=UserFeatureView.FEATURE_1
)
# Option 2
self.freeze_time(self.now)
ufv = UserFeatureView.objects.get_or_create(
user=self.shift.worker, feature=UserFeatureView.FEATURE_1
)
...
expect(ufv.date_created).to(equal(self.now))
Wrong ⚠️
from django.utils import timezone
from instawork.tests import PatchingTestCase
class UserFeatureViewTests(PatchingTestCase):
def setUp(self):
self.now = timezone.now()
self.mock_call = self.patch("django.utils.timezone.now", return_value=self.now)
def test_feature_view(self):
ufv = UserFeatureView.objects.get_or_create(
user=self.shift.worker, feature=UserFeatureView.FEATURE_1
)
...
expect(ufv.date_created).to(equal(self.now))
Lint check to prevent error logging without exception info.
Recommendation: Add exc_info=True keyword argument in logger.error()
Correct ✅
import logging
custom_logger = logging.getLogger("module.logger")
class UserFeatureView(Model):
def save(self):
try:
...
except ValueError as e:
custom_logger.error(e, exc_info=True)
return name
Wrong ⚠️
import logging
custom_logger = logging.getLogger("module.logger")
class UserFeatureView(Model):
def save(self):
try:
...
except ValueError as e:
custom_logger.error(e)
return name
Lint to avoid usage of datetime.now() which does not contain timezone information and causes various warnings in tests. Use timezone.now() instead.
Correct ✅
from django.utils import timezone
now = timezone.now()
Wrong ⚠️
from datetime import datetime
now = datetime.now()
Lint to avoid usage of datetime.replace(tzinfo=XXX) which is not a viable way of setting timezones with python/pytz.
Correct ✅
import pytz
from django.utils import timezone
tz = pytz.timezone("America/Los_Angeles")
now_pt = timezone.now().astimezone(tz)
Wrong ⚠️
import pytz
from django.utils import timezone
tz = pytz.timezone("America/Los_Angeles")
now_pt = timezone.now().replace(tzinfo=tz)
Lint to avoid usage of Model.objects.bulk_update / Model.objects.bulk_create. Use Model.objects.bulk_update(batch_size=X) / Model.objects.bulk_create(batch_size=X) instead.
Correct ✅
# Bulk update
Model.objects.bulk_update([obj1, obj2, ...], batch_size=10)
# Bulk create
Model.objects.bulk_create([obj1, obj2, ...], batch_size=10)
Wrong ⚠️
# Bulk update
Model.objects.bulk_update([obj1, obj2, ...])
# Bulk create
Model.objects.bulk_create([obj1, obj2, ...])
Use our internal decorator instead: instawork.decorators.shared_task.
Correct ✅
from instawork.decorators import shared_task
@shared_task
def my_task():
pass
Wrong ⚠️
from celery import shared_task
@shared_task
def my_task():
pass
Lint to avoid usage of timezone.activate() and instead use with timezone.override(). This is to avoid timezone
leakage between different tests and features.
Correct ✅
from django.utils import timezone
with timezone.override(zoneinfo.ZoneInfo(tzname)):
<Rest of the code>
Wrong ⚠️
from django.utils import timezone
timezone.activate(zoneinfo.ZoneInfo(tzname))
<Rest of the code>
timezone.deactivate()
It's required to pass db_constraint=False when creating a new foreign key relationship. This is to prevent issues with online schema changes that arise due to MySQL's foreign key architecture.
Correct ✅
x = models.ForeignKey(db_constraint=False, on_delete=models.CASCADE)
Wrong ⚠️
x = models.ForeignKey(on_delete=models.CASCADE)
It's not advisable to use DO_NOTHING on foreign keys because we have removed foreign key constraints in the database. It's best to have a strategy that deals with deletions that doesn't leave "orphaned" foreign key ids.
Correct ✅
x = models.ForeignKey(db_constraint=False, on_delete=models.CASCADE)
Wrong ⚠️
x = models.ForeignKey(db_constraint=False, on_delete=models.DO_NOTHING)
Use Options.indexes to define an index rather than argument on field.
See here
Correct ✅
x = models.CharField()
class Meta:
indexes = [
models.Index(fields=["x"], name="x_idx"),
]
Wrong ⚠️
x = models.CharField(db_index=True)
Use Options.constraints to define uniqueness rather than argument on field.
See here
and here
Correct ✅
x = models.CharField()
class Meta:
constraints = [
models.UniqueConstraint(fields=["x"], name="unique_x"),
]
Wrong ⚠️
x = models.CharField(unique=True)
Use Options.indexes to define an index rather than argument on field.
See here
Correct ✅
class Meta:
indexes = [
models.Index(fields=["a", "b"], name="a_b_idx"),
]
Wrong ⚠️
class Meta:
index_together = (("a", "b"))
Use Options.constraints to define uniqueness rather than argument on field.
See here
and here
Correct ✅
class Meta:
constraints = [
models.UniqueConstraint(fields=["a", "b"], name="unique_a_b"),
]
Wrong ⚠️
class Meta:
unique_together = (("a", "b"))
Use LazyAttribute or LazyFunction in factories with timezone.now to enable freezegun and avoid unexpected datetimes.
Correct ✅
class TestFactory(factory.django.DjangoModelFactory):
starts_at = factory.LazyFunction(timezone.now)
Wrong ⚠️
class TestFactory(factory.django.DjangoModelFactory):
starts_at = timezone.now()
Avoid using setUpClass and tearDownClass inside a test case
Correct ✅
class MyTest(TestCase):
def setUpTestData(self):
something()
Wrong ⚠️
class MyTest(TestCase):
@classmethod
def setUpClass(self):
something()
@classmethod
def tearDownClass(self):
something()
parameterized.expand() must be above override_config, override_settings, etc. Parameterized
does some low-level manipulation and copies functions in a way that may not be compatible with the
way that override decorators work.
Correct ✅
class MyTest(TestCase):
@parameterized.expand([(1,2)])
@override_config(SOME_CONFIG=1)
def test_something(self, p1, p2):
something()
Wrong ⚠️
class MyTest(TestCase):
@override_config(SOME_CONFIG=1)
@parameterized.expand([(1,2)])
def test_something(self, p1, p2):
something()
It's easy to forget to reset a value back to the default when directly overriding it. The decorator automatically resets the value back to the previous state once the test is complete and is thus much safer.
Correct ✅
class MyTest(TestCase):
@override_config(SOME_CONFIG=1)
def test_something(self):
something()
Wrong ⚠️
class MyTest(TestCase):
def test_something(self):
config.SOME_CONFIG = 1
something()
FAQs
A plugin to show lint errors for IW
We found that flake8-iw demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 3 open source maintainers collaborating on the project.
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