Fix file sensor reading the whole file to get the last line (#73986)

homeassistant/components/file/manifest.json

@@ -3,5 +3,6 @@
   "name": "File",
   "documentation": "https://www.home-assistant.io/integrations/file",
   "codeowners": ["@fabaff"],
-  "iot_class": "local_polling"
+  "iot_class": "local_polling",
+  "requirements": ["file-read-backwards==2.0.0"]
 }

homeassistant/components/file/sensor.py

@@ -4,6 +4,7 @@ from __future__ import annotations
 import logging
 import os
 
+from file_read_backwards import FileReadBackwards
 import voluptuous as vol
 
 from homeassistant.components.sensor import PLATFORM_SCHEMA, SensorEntity
@@ -77,9 +78,10 @@ class FileSensor(SensorEntity):
     def update(self):
         """Get the latest entry from a file and updates the state."""
         try:
-            with open(self._file_path, encoding="utf-8") as file_data:
+            with FileReadBackwards(self._file_path, encoding="utf-8") as file_data:
                 for line in file_data:
                     data = line
+                    break
                 data = data.strip()
         except (IndexError, FileNotFoundError, IsADirectoryError, UnboundLocalError):
             _LOGGER.warning(

requirements_all.txt

@@ -637,6 +637,9 @@ feedparser==6.0.2
 # homeassistant.components.fibaro
 fiblary3==0.1.8
 
+# homeassistant.components.file
+file-read-backwards==2.0.0
+
 # homeassistant.components.fints
 fints==3.1.0
 

requirements_test_all.txt

@@ -455,6 +455,9 @@ feedparser==6.0.2
 # homeassistant.components.fibaro
 fiblary3==0.1.8
 
+# homeassistant.components.file
+file-read-backwards==2.0.0
+
 # homeassistant.components.fivem
 fivem-api==0.1.2
 

tests/components/file/fixtures/file_value.txt

@@ -0,0 +1,3 @@
+43
+45
+21

tests/components/file/fixtures/file_value_template.txt

@@ -0,0 +1,2 @@
+{"temperature": 29, "humidity": 31}
+{"temperature": 26, "humidity": 36}

tests/components/file/test_sensor.py

@@ -1,5 +1,5 @@
 """The tests for local file sensor platform."""
-from unittest.mock import Mock, mock_open, patch
+from unittest.mock import Mock, patch
 
 import pytest
 
@@ -7,7 +7,7 @@ from homeassistant.const import STATE_UNKNOWN
 from homeassistant.core import HomeAssistant
 from homeassistant.setup import async_setup_component
 
-from tests.common import mock_registry
+from tests.common import get_fixture_path, mock_registry
 
 
 @pytest.fixture
@@ -21,13 +21,14 @@ def entity_reg(hass):
 async def test_file_value(hass: HomeAssistant) -> None:
     """Test the File sensor."""
     config = {
-        "sensor": {"platform": "file", "name": "file1", "file_path": "mock.file1"}
+        "sensor": {
+            "platform": "file",
+            "name": "file1",
+            "file_path": get_fixture_path("file_value.txt", "file"),
+        }
     }
 
-    m_open = mock_open(read_data="43\n45\n21")
+    with patch.object(hass.config, "is_allowed_path", return_value=True):
-    with patch(
-        "homeassistant.components.file.sensor.open", m_open, create=True
-    ), patch.object(hass.config, "is_allowed_path", return_value=True):
         assert await async_setup_component(hass, "sensor", config)
         await hass.async_block_till_done()
 
@@ -43,19 +44,12 @@ async def test_file_value_template(hass: HomeAssistant) -> None:
         "sensor": {
             "platform": "file",
             "name": "file2",
-            "file_path": "mock.file2",
+            "file_path": get_fixture_path("file_value_template.txt", "file"),
             "value_template": "{{ value_json.temperature }}",
         }
     }
 
-    data = (
+    with patch.object(hass.config, "is_allowed_path", return_value=True):
-        '{"temperature": 29, "humidity": 31}\n' + '{"temperature": 26, "humidity": 36}'
-    )
-
-    m_open = mock_open(read_data=data)
-    with patch(
-        "homeassistant.components.file.sensor.open", m_open, create=True
-    ), patch.object(hass.config, "is_allowed_path", return_value=True):
         assert await async_setup_component(hass, "sensor", config)
         await hass.async_block_till_done()
 
@@ -67,12 +61,15 @@ async def test_file_value_template(hass: HomeAssistant) -> None:
 @patch("os.access", Mock(return_value=True))
 async def test_file_empty(hass: HomeAssistant) -> None:
     """Test the File sensor with an empty file."""
-    config = {"sensor": {"platform": "file", "name": "file3", "file_path": "mock.file"}}
+    config = {
+        "sensor": {
+            "platform": "file",
+            "name": "file3",
+            "file_path": get_fixture_path("file_empty.txt", "file"),
+        }
+    }
 
-    m_open = mock_open(read_data="")
+    with patch.object(hass.config, "is_allowed_path", return_value=True):
-    with patch(
-        "homeassistant.components.file.sensor.open", m_open, create=True
-    ), patch.object(hass.config, "is_allowed_path", return_value=True):
         assert await async_setup_component(hass, "sensor", config)
         await hass.async_block_till_done()
 
@@ -85,13 +82,14 @@ async def test_file_empty(hass: HomeAssistant) -> None:
 async def test_file_path_invalid(hass: HomeAssistant) -> None:
     """Test the File sensor with invalid path."""
     config = {
-        "sensor": {"platform": "file", "name": "file4", "file_path": "mock.file4"}
+        "sensor": {
+            "platform": "file",
+            "name": "file4",
+            "file_path": get_fixture_path("file_value.txt", "file"),
+        }
     }
 
-    m_open = mock_open(read_data="43\n45\n21")
+    with patch.object(hass.config, "is_allowed_path", return_value=False):
-    with patch(
-        "homeassistant.components.file.sensor.open", m_open, create=True
-    ), patch.object(hass.config, "is_allowed_path", return_value=False):
         assert await async_setup_component(hass, "sensor", config)
         await hass.async_block_till_done()