Accept function for FileSink rotation argument

loguru/__init__.py

@@ -269,6 +269,15 @@ def function(message):
                     self.rotation_time = time_limit
                     return True
                 return False
+        elif callable(rotation):
+            time_limit = rotation(self.start_time)
+            def function(message):
+                nonlocal time_limit
+                record_time = message.record['time']
+                if record_time >= time_limit:
+                    time_limit = rotation(record_time)
+                    return True
+                return False
         else:
             raise ValueError("Cannot infer rotation for objects of type: '%s'" % type(rotation))
 

tests/test_rotation.py

@@ -90,6 +90,7 @@ def test_size_rotation(tmpdir, logger, size):
     ("1.222 hours, 3.44s", [1.222, 0.1, 1, 1.2, 2]),
     (datetime.timedelta(hours=1), [0.9, 0.2, 0.7, 0.5, 3]),
     (pendulum.Interval(minutes=30), [0.48, 0.04, 0.07, 0.44, 0.5]),
+    (lambda t: t.add(months=1).start_of('month').at(13, 00, 00), [12 * 24, 26, 31 * 24 - 2, 2, 24 * 60]),
 ])
 def test_time_rotation(monkeypatch, tmpdir, when, hours, logger):
     now = pendulum.parse("2017-06-18 12:00:00")  # Sunday