timedelta: support microseconds and negative values (#795)

ref: PyMySQL/PyMySQL#1262

Author: methane

src/MySQLdb/times.py

@@ -38,10 +38,20 @@ def TimestampFromTicks(ticks):
 
 
 def format_TIMEDELTA(v):
-    seconds = int(v.seconds) % 60
-    minutes = int(v.seconds // 60) % 60
-    hours = int(v.seconds // 3600) % 24
-    return "%d %d:%d:%d" % (v.days, hours, minutes, seconds)
+    # Negative timedeltas store the sign in days and keep seconds positive.
+    # Format the absolute value so the sign is not applied twice by MySQL.
+    sign = ""
+    if v.days < 0:
+        sign = "-"
+        v = abs(v)
+
+    micros = v.microseconds
+    minutes, seconds = divmod(v.seconds, 60)
+    hours, minutes = divmod(minutes, 60)
+
+    if micros:
+        return f"{sign}{v.days} {hours}:{minutes}:{seconds}.{micros:06d}"
+    return f"{sign}{v.days} {hours}:{minutes}:{seconds}"
 
 
 def format_TIMESTAMP(d):

tests/test_MySQLdb_times.py

@@ -120,6 +120,7 @@ def test_datetime_to_literal(self):
     def test_datetimedelta_to_literal(self):
         d = datetime(2015, 12, 13, 1, 2, 3) - datetime(2015, 12, 13, 1, 2, 2)
         assert times.DateTimeDelta2literal(d, "") == b"'0 0:0:1'"
+        assert times.DateTimeDelta2literal(-timedelta(minutes=30), "") == b"'-0 0:30:0'"
 
 
 class TestFormat(unittest.TestCase):
@@ -131,7 +132,13 @@ def test_format_timedelta(self):
         assert times.format_TIMEDELTA(d) == "0 2:2:2"
 
         d = datetime(2015, 1, 1, 10, 11, 12) - datetime(2015, 1, 1, 11, 12, 13)
-        assert times.format_TIMEDELTA(d) == "-1 22:58:59"
+        assert times.format_TIMEDELTA(d) == "-0 1:1:1"
+
+        assert times.format_TIMEDELTA(-timedelta(minutes=30)) == "-0 0:30:0"
+        assert times.format_TIMEDELTA(-timedelta(days=1, hours=2)) == "-1 2:0:0"
+        d = timedelta(seconds=83579, microseconds=51000)
+        assert times.format_TIMEDELTA(d) == "0 23:12:59.051000"
+        assert times.format_TIMEDELTA(-d) == "-0 23:12:59.051000"
 
     def test_format_timestamp(self):
         assert times.format_TIMESTAMP(datetime(2015, 2, 3)) == "2015-02-03 00:00:00"