From d370d9b0160634d311563b82f18b2020a897a964 Mon Sep 17 00:00:00 2001
From: Chris White <chris@prefect.io>
Date: Tue, 13 Oct 2020 12:03:18 -0700
Subject: [PATCH] Allow for None as labels attribute of clocks

---
 src/prefect/schedules/clocks.py       |  4 ++--
 tests/schedules/test_clocks.py        | 16 ++++++++--------
 tests/serialization/test_schedules.py |  1 +
 3 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/src/prefect/schedules/clocks.py b/src/prefect/schedules/clocks.py
index 12140669b05e..5b6527f4e50d 100644
--- a/src/prefect/schedules/clocks.py
+++ b/src/prefect/schedules/clocks.py
@@ -19,7 +19,7 @@ def __init__(
     ) -> None:
         self.start_time = start_time
         self.parameter_defaults = parameter_defaults or dict()
-        self.labels = labels or []
+        self.labels = labels
 
     def __eq__(self, other: Any) -> bool:
         if not isinstance(other, (ClockEvent, datetime)):
@@ -82,7 +82,7 @@ def __init__(
         self.start_date = start_date
         self.end_date = end_date
         self.parameter_defaults = parameter_defaults or dict()
-        self.labels = labels or []
+        self.labels = labels
 
     def events(self, after: datetime = None) -> Iterable[ClockEvent]:
         """
diff --git a/tests/schedules/test_clocks.py b/tests/schedules/test_clocks.py
index 84649a70a5c3..2d05c4b47f85 100644
--- a/tests/schedules/test_clocks.py
+++ b/tests/schedules/test_clocks.py
@@ -33,7 +33,7 @@ def test_clock_event_requires_start_time(self):
 
         assert e.start_time == now
         assert e.parameter_defaults == dict()
-        assert e.labels == []
+        assert e.labels is None
 
     def test_clock_event_accepts_parameters(self):
         now = pendulum.now("UTC")
@@ -41,7 +41,7 @@ def test_clock_event_accepts_parameters(self):
 
         assert e.start_time == now
         assert e.parameter_defaults == dict(x=42, z=[1, 2, 3])
-        assert e.labels == []
+        assert e.labels is None
 
     def test_clock_event_accepts_labels(self):
         now = pendulum.now("UTC")
@@ -117,7 +117,7 @@ def test_create_interval_clock(self):
             start_date=pendulum.now("UTC"), interval=timedelta(days=1)
         )
         assert c.parameter_defaults == dict()
-        assert c.labels == []
+        assert c.labels is None
 
     def test_create_interval_clock_with_parameters(self):
         c = clocks.IntervalClock(
@@ -145,7 +145,7 @@ def test_start_date_can_be_none(self):
         assert c.interval == timedelta(hours=1)
         assert c.end_date is None
         assert c.parameter_defaults == dict()
-        assert c.labels == []
+        assert c.labels is None
 
     def test_end_date(self):
         c = clocks.IntervalClock(
@@ -155,7 +155,7 @@ def test_end_date(self):
         assert c.interval == timedelta(hours=1)
         assert c.end_date == pendulum.datetime(2020, 1, 1)
         assert c.parameter_defaults == dict()
-        assert c.labels == []
+        assert c.labels is None
 
     def test_interval_clock_interval_must_be_positive(self):
         with pytest.raises(ValueError, match="greater than 0"):
@@ -384,7 +384,7 @@ class TestCronClock:
     def test_create_cron_clock(self):
         c = clocks.CronClock("* * * * *")
         assert c.parameter_defaults == dict()
-        assert c.labels == []
+        assert c.labels is None
 
     def test_create_cron_clock_with_parameters(self):
         c = clocks.CronClock("* * * * *", parameter_defaults=dict(x=42))
@@ -625,7 +625,7 @@ def test_create_dates_clock_one_date(self):
         clock = clocks.DatesClock(dates=[now])
         assert clock.start_date == clock.end_date == now
         assert clock.parameter_defaults == dict()
-        assert clock.labels == []
+        assert clock.labels is None
 
     def test_create_dates_clock_multiple_dates(self):
         now = pendulum.now("UTC")
@@ -633,7 +633,7 @@ def test_create_dates_clock_multiple_dates(self):
         assert clock.start_date == now
         assert clock.end_date == now.add(days=2)
         assert clock.parameter_defaults == dict()
-        assert clock.labels == []
+        assert clock.labels is None
 
     def test_create_dates_clock_multiple_dates_with_parameters(self):
         now = pendulum.now("UTC")
diff --git a/tests/serialization/test_schedules.py b/tests/serialization/test_schedules.py
index db8deea9c1ed..e86806b9a343 100644
--- a/tests/serialization/test_schedules.py
+++ b/tests/serialization/test_schedules.py
@@ -37,6 +37,7 @@ def test_serialize_schedule_with_parameters():
 
     output = s2.next(3, after=dt, return_events=True)
 
+    assert all([e.labels is None for e in output])
     assert all([isinstance(e, clocks.ClockEvent) for e in output])