Add no data exception on watermeter (#208)

* Add no data exception

* Add extra test to cover the code

p1monitor/__init__.py

@@ -1,13 +1,14 @@
 """Asynchronous Python client for the P1 Monitor API."""
 
-from .exceptions import P1MonitorConnectionError, P1MonitorError
+from .exceptions import P1MonitorConnectionError, P1MonitorError, P1MonitorNoDataError
 from .models import Phases, Settings, SmartMeter, WaterMeter
 from .p1monitor import P1Monitor
 
 __all__ = [
     "P1Monitor",
     "P1MonitorError",
     "P1MonitorConnectionError",
+    "P1MonitorNoDataError",
     "SmartMeter",
     "Settings",
     "Phases",

p1monitor/exceptions.py

@@ -7,3 +7,7 @@ class P1MonitorError(Exception):
 
 class P1MonitorConnectionError(P1MonitorError):
     """P1 Monitor connection exception."""
+
+
+class P1MonitorNoDataError(P1MonitorError):
+    """P1 Monitor no data exception."""

p1monitor/p1monitor.py

@@ -14,7 +14,7 @@
 from aiohttp import hdrs
 from yarl import URL
 
-from .exceptions import P1MonitorConnectionError, P1MonitorError
+from .exceptions import P1MonitorConnectionError, P1MonitorError, P1MonitorNoDataError
 from .models import Phases, Settings, SmartMeter, WaterMeter
 
 
@@ -125,10 +125,15 @@ async def watermeter(self) -> WaterMeter:
 
         Returns:
             A WaterMeter data object from the P1 Monitor API.
+
+        Raises:
+            P1MonitorNoDataError: No data was received from the P1 Monitor API.
         """
         data = await self._request(
             "v2/watermeter/day", params={"json": "object", "limit": 1}
         )
+        if data == []:
+            raise P1MonitorNoDataError("No data received from P1 Monitor")
         return WaterMeter.from_dict(data)
 
     async def close(self) -> None:

tests/fixtures/no_data.json

@@ -0,0 +1 @@
+[]

tests/test_models.py

@@ -3,7 +3,14 @@
 import pytest
 from aresponses import ResponsesMockServer
 
-from p1monitor import P1Monitor, Phases, Settings, SmartMeter, WaterMeter
+from p1monitor import (
+    P1Monitor,
+    P1MonitorNoDataError,
+    Phases,
+    Settings,
+    SmartMeter,
+    WaterMeter,
+)
 
 from . import load_fixtures
 
@@ -83,6 +90,27 @@ async def test_watermeter(aresponses: ResponsesMockServer) -> None:
         assert watermeter.pulse_count == 128
 
 
+@pytest.mark.asyncio
+async def test_no_watermeter_data(aresponses: ResponsesMockServer) -> None:
+    """Test no WaterMeter data from P1 Monitor device."""
+    aresponses.add(
+        "example.com",
+        "/api/v2/watermeter/day",
+        "GET",
+        aresponses.Response(
+            text=load_fixtures("no_data.json"),
+            status=200,
+            headers={"Content-Type": "application/json; charset=utf-8"},
+        ),
+    )
+
+    async with aiohttp.ClientSession() as session:
+        client = P1Monitor(host="example.com", session=session)
+        with pytest.raises(P1MonitorNoDataError):
+            watermeter: WaterMeter = await client.watermeter()
+            assert not watermeter
+
+
 @pytest.mark.asyncio
 async def test_settings(aresponses: ResponsesMockServer) -> None:
     """Test request from a P1 Monitor device - Settings object."""