Invalidate importlib cache before reloading modules

src/components/monitors_loader/monitors_loader.py

@@ -1,4 +1,5 @@
 import asyncio
+import importlib
 import logging
 import shutil
 from datetime import datetime, timedelta
@@ -221,6 +222,8 @@ async def _load_monitors() -> None:
                 additional_files=code_module.additional_files,
             )
 
+    importlib.invalidate_caches()
+
     for monitor in loaded_monitors:
         with catch_exceptions(_logger):
             monitor_path = monitors_paths.get(monitor.id)

tests/components/monitors_loader/test_monitors_loader.py

@@ -1,9 +1,10 @@
 import asyncio
+import importlib
 import sys
 from datetime import datetime, timezone
 from pathlib import Path
 from types import ModuleType
-from unittest.mock import AsyncMock
+from unittest.mock import AsyncMock, MagicMock
 
 import pytest
 
@@ -537,9 +538,11 @@ def reactions_list(self):
     assert monitor_module.reaction_options.alert_solved == [do_nothing, "do_nothing"]
 
 
-async def test_load_monitors(clear_database):
+async def test_load_monitors(mocker, clear_database):
     """'_load_monitors' should load all enabled monitors from the database and add them to the
     registry"""
+    invalidate_caches_spy: MagicMock = mocker.spy(importlib, "invalidate_caches")
+
     await databases.execute_application(
         'insert into "Monitors"(id, name, enabled) values'
         "(9999123, 'monitor_1', true),"
@@ -555,6 +558,8 @@ async def test_load_monitors(clear_database):
 
     await monitors_loader._load_monitors()
 
+    invalidate_caches_spy.assert_called_once()
+
     assert len(registry._monitors) == 2
     assert isinstance(registry._monitors[9999123]["module"], ModuleType)
     assert isinstance(registry._monitors[9999456]["module"], ModuleType)

tests/module_loader/test_loader.py

@@ -1,3 +1,4 @@
+import importlib
 import os
 import sys
 import time
@@ -134,10 +135,44 @@ def test_load_module_from_file(caplog):
         (10, 200),
     ],
 )
-def test_load_module_from_file_reload(caplog, n1, n2):
+def test_load_module_from_file_reload_invalidate_cache(caplog, n1, n2):
     """'load_module_from_file' should be able to reload modules that were previously loaded,
-    allowing hot changes"""
-    module_name = f"load_module_from_file_reload_{n1}_{n2}"
+    allowing hot changes.
+    To be able reload a file the file timestamp or size must change, or the cache must be
+    invalidated"""
+    module_name = f"test_load_module_from_file_reload_invalidate_cache_{n1}_{n2}"
+    module_code = "def get_value(): return {n}"
+
+    module_path = loader.create_module_files(module_name, module_code.format(n=n1))
+
+    module = loader.load_module_from_file(module_path)
+
+    assert module.get_value() == n1
+    assert_message_in_log(caplog, f"Monitor '{module_name}' loaded")
+
+    importlib.invalidate_caches()
+
+    module_path = loader.create_module_files(module_name, module_code.format(n=n2))
+
+    module = loader.load_module_from_file(module_path)
+
+    assert module.get_value() == n2
+    assert_message_in_log(caplog, f"Monitor '{module_name}' loaded", count=2)
+
+
+@pytest.mark.parametrize(
+    "n1, n2",
+    [
+        (10, 99),  # In this test case, the file size doesn't change
+        (10, 200),
+    ],
+)
+def test_load_module_from_file_reload_sleep(caplog, n1, n2):
+    """'load_module_from_file' should be able to reload modules that were previously loaded,
+    allowing hot changes.
+    To be able reload a file the file timestamp or size must change, or the cache must be
+    invalidated"""
+    module_name = f"test_load_module_from_file_reload_sleep_{n1}_{n2}"
     module_code = "def get_value(): return {n}"
 
     module_path = loader.create_module_files(module_name, module_code.format(n=n1))
@@ -147,7 +182,6 @@ def test_load_module_from_file_reload(caplog, n1, n2):
     assert module.get_value() == n1
     assert_message_in_log(caplog, f"Monitor '{module_name}' loaded")
 
-    # As python checks for the timestamp to change to reload a module, sleep for 1 second
     time.sleep(1)
 
     module_path = loader.create_module_files(module_name, module_code.format(n=n2))
@@ -158,6 +192,31 @@ def test_load_module_from_file_reload(caplog, n1, n2):
     assert_message_in_log(caplog, f"Monitor '{module_name}' loaded", count=2)
 
 
+@pytest.mark.flaky(reruns=1)
+def test_load_module_from_file_reload_no_time_change(caplog):
+    """'load_module_from_file' should not reload the file if the file timestamp or size didn't
+    change."""
+    module_name = "test_load_module_from_file_reload_no_time_change"
+    module_code = "def get_value(): return {n}"
+
+    module_path = loader.create_module_files(module_name, module_code.format(n=10))
+
+    module = loader.load_module_from_file(module_path)
+
+    assert module.get_value() == 10
+    assert_message_in_log(caplog, f"Monitor '{module_name}' loaded")
+
+    time.sleep(0.1)
+
+    module_path = loader.create_module_files(module_name, module_code.format(n=99))
+
+    module = loader.load_module_from_file(module_path)
+
+    # The value didn't change, even though the module code changed
+    assert module.get_value() == 10
+    assert_message_in_log(caplog, f"Monitor '{module_name}' loaded", count=2)
+
+
 def test_load_module_from_file_reload_replace_variables():
     """'load_module_from_file' should be able to reload modules replacing the previous state for a
     new one"""