Fix `format_timedelta` function's parsing of negative timedeltas (#5740)

* Fix `format_timedelta` function's parsing of negative timedeltas.

The entire timedelta can be negative.

* Refactor to use a single timedelta regular expression.

* Fix typo in `format_timedelta` function argument.

bigquery_etl/query_scheduling/formatters.py

@@ -1,9 +1,9 @@
 """This file contains custom filters for formatting data types in Jinja templates."""
 
-import re
 from datetime import datetime, timedelta
 
 from bigquery_etl import query_scheduling
+from bigquery_etl.query_scheduling.utils import TIMEDELTA_RE
 
 
 def format_schedule_interval(interval):
@@ -36,20 +36,18 @@ def format_date(date_string):
 
 # based on https://stackoverflow.com/questions/4628122/how-to-construct-a
 # -timedelta-object-from-a-simple-string
-def format_timedelta(timdelta_string):
+def format_timedelta(timedelta_string):
     """Format a timedelta object."""
-    timedelta_regex = re.compile(
-        r"^((?P<hours>-?\d+?)h)?((?P<minutes>-?\d+?)m)?((?P<seconds>-?\d+?)s)?$"
-    )
-    parts = timedelta_regex.match(timdelta_string)
+    parts = TIMEDELTA_RE.match(timedelta_string)
     if not parts:
-        return timdelta_string
+        return timedelta_string
 
     parts = parts.groupdict()
+    is_negative = timedelta_string.startswith("-")
     time_params = {}
     for name, param in parts.items():
         if param:
-            time_params[name] = int(param)
+            time_params[name] = int(param) * (-1 if is_negative else 1)
 
     return timedelta(**time_params)
 

bigquery_etl/query_scheduling/utils.py

@@ -3,6 +3,10 @@
 import re
 from datetime import datetime
 
+TIMEDELTA_RE = re.compile(
+    r"^-?((?P<hours>\d+)h)?((?P<minutes>\d+)m)?((?P<seconds>\d+)s)?$"
+)
+
 
 def is_timedelta_string(s):
     """
@@ -10,8 +14,7 @@ def is_timedelta_string(s):
 
     Timedeltas in configs are specified like: 1h, 30m, 1h15m, ...
     """
-    timedelta_regex = re.compile(r"^-?(\d+h)?(\d+m)?(\d+s)?$")
-    return timedelta_regex.match(s)
+    return TIMEDELTA_RE.match(s)
 
 
 def validate_timedelta_string(s):

tests/query_scheduling/test_formatters.py

@@ -43,10 +43,15 @@ class TestFormatters:
             assert format_timedelta(123)
 
         assert format_timedelta("1h") == datetime.timedelta(seconds=3600)
+        assert format_timedelta("-1h") == datetime.timedelta(seconds=-3600)
         assert format_timedelta("15m") == datetime.timedelta(seconds=900)
+        assert format_timedelta("-15m") == datetime.timedelta(seconds=-900)
         assert format_timedelta("1h15m") == datetime.timedelta(seconds=4500)
+        assert format_timedelta("-1h15m") == datetime.timedelta(seconds=-4500)
         assert format_timedelta("1s") == datetime.timedelta(seconds=1)
+        assert format_timedelta("-1s") == datetime.timedelta(seconds=-1)
         assert format_timedelta("1h1m1s") == datetime.timedelta(seconds=3661)
+        assert format_timedelta("-1h1m1s") == datetime.timedelta(seconds=-3661)
         assert format_timedelta("1d1h1m1s") == "1d1h1m1s"
 
     def test_format_optional_string(self):