fan: Ability to disable delayed turn off functionality (#741)

* Added ability to disable delayed turn off functionality

When 0 is passed, delay turn off is disabled. Before this, if delay off was set, it could not be unset.

* Update test_fan.py

* Update test_fan.py

miio/fan.py

@@ -548,7 +548,7 @@ def set_child_lock(self, lock: bool):
     def delay_off(self, seconds: int):
         """Set delay off seconds."""
 
-        if seconds < 1:
+        if seconds < 0:
             raise FanException("Invalid value for a delayed turn off: %s" % seconds)
 
         return self.send("set_poweroff_time", [seconds])
@@ -755,7 +755,7 @@ def set_child_lock(self, lock: bool):
     def delay_off(self, minutes: int):
         """Set delay off minutes."""
 
-        if minutes < 1:
+        if minutes < 0:
             raise FanException("Invalid value for a delayed turn off: %s" % minutes)
 
         return self.send("s_t_off", [minutes])

miio/tests/test_fan.py

@@ -259,13 +259,12 @@ def delay_off_countdown():
         assert delay_off_countdown() == 100
         self.device.delay_off(200)
         assert delay_off_countdown() == 200
+        self.device.delay_off(0)
+        assert delay_off_countdown() == 0
 
         with pytest.raises(FanException):
             self.device.delay_off(-1)
 
-        with pytest.raises(FanException):
-            self.device.delay_off(0)
-
 
 class DummyFanV3(DummyDevice, Fan):
     def __init__(self, *args, **kwargs):
@@ -513,13 +512,12 @@ def delay_off_countdown():
         assert delay_off_countdown() == 100
         self.device.delay_off(200)
         assert delay_off_countdown() == 200
+        self.device.delay_off(0)
+        assert delay_off_countdown() == 0
 
         with pytest.raises(FanException):
             self.device.delay_off(-1)
 
-        with pytest.raises(FanException):
-            self.device.delay_off(0)
-
 
 class DummyFanSA1(DummyDevice, Fan):
     def __init__(self, *args, **kwargs):
@@ -729,13 +727,12 @@ def delay_off_countdown():
         assert delay_off_countdown() == 100
         self.device.delay_off(200)
         assert delay_off_countdown() == 200
+        self.device.delay_off(0)
+        assert delay_off_countdown() == 0
 
         with pytest.raises(FanException):
             self.device.delay_off(-1)
 
-        with pytest.raises(FanException):
-            self.device.delay_off(0)
-
 
 class DummyFanP5(DummyDevice, FanP5):
     def __init__(self, *args, **kwargs):
@@ -912,9 +909,8 @@ def delay_off_countdown():
         assert delay_off_countdown() == 100
         self.device.delay_off(200)
         assert delay_off_countdown() == 200
+        self.device.delay_off(0)
+        assert delay_off_countdown() == 0
 
         with pytest.raises(FanException):
             self.device.delay_off(-1)
-
-        with pytest.raises(FanException):
-            self.device.delay_off(0)