Enable open protection in the event loop

homeassistant/block_async_io.py

@@ -1,5 +1,6 @@
 """Block blocking calls being done in asyncio."""
 
+import builtins
 from contextlib import suppress
 from http.client import HTTPConnection
 import importlib
@@ -13,12 +14,21 @@
 
 _IN_TESTS = "unittest" in sys.modules
 
+ALLOWED_FILE_PREFIXES = ("/proc",)
+
 
 def _check_import_call_allowed(mapped_args: dict[str, Any]) -> bool:
     # If the module is already imported, we can ignore it.
     return bool((args := mapped_args.get("args")) and args[0] in sys.modules)
 
 
+def _check_file_allowed(mapped_args: dict[str, Any]) -> bool:
+    # If the file is in /proc we can ignore it.
+    args = mapped_args["args"]
+    path = args[0] if type(args[0]) is str else str(args[0])  # noqa: E721
+    return path.startswith(ALLOWED_FILE_PREFIXES)
+
+
 def _check_sleep_call_allowed(mapped_args: dict[str, Any]) -> bool:
     #
     # Avoid extracting the stack unless we need to since it
@@ -50,11 +60,15 @@ def enable() -> None:
         loop_thread_id=loop_thread_id,
     )
 
-    # Currently disabled. pytz doing I/O when getting timezone.
-    # Prevent files being opened inside the event loop
-    # builtins.open = protect_loop(builtins.open)
-
     if not _IN_TESTS:
+        # Prevent files being opened inside the event loop
+        builtins.open = protect_loop(  # type: ignore[assignment]
+            builtins.open,
+            strict_core=False,
+            strict=False,
+            check_allowed=_check_file_allowed,
+            loop_thread_id=loop_thread_id,
+        )
         # unittest uses `importlib.import_module` to do mocking
         # so we cannot protect it if we are running tests
         importlib.import_module = protect_loop(

tests/test_block_async_io.py

@@ -1,7 +1,10 @@
 """Tests for async util methods from Python source."""
 
+import contextlib
 import importlib
+from pathlib import Path, PurePosixPath
 import time
+from typing import Any
 from unittest.mock import Mock, patch
 
 import pytest
@@ -198,3 +201,37 @@ async def test_protect_loop_importlib_import_module_in_integration(
         "Detected blocking call to import_module inside the event loop by "
         "integration 'hue' at homeassistant/components/hue/light.py, line 23"
     ) in caplog.text
+
+
+async def test_protect_loop_open(caplog: pytest.LogCaptureFixture) -> None:
+    """Test open of a file in /proc is not reported."""
+    block_async_io.enable()
+    with contextlib.suppress(FileNotFoundError):
+        open("/proc/does_not_exist").close()
+    assert "Detected blocking call to open with args" not in caplog.text
+
+
+async def test_protect_open(caplog: pytest.LogCaptureFixture) -> None:
+    """Test opening a file in the event loop logs."""
+    block_async_io.enable()
+    with contextlib.suppress(FileNotFoundError):
+        open("/config/data_not_exist").close()
+
+    assert "Detected blocking call to open with args" in caplog.text
+
+
+@pytest.mark.parametrize(
+    "path",
+    [
+        "/config/data_not_exist",
+        Path("/config/data_not_exist"),
+        PurePosixPath("/config/data_not_exist"),
+    ],
+)
+async def test_protect_open_path(path: Any, caplog: pytest.LogCaptureFixture) -> None:
+    """Test opening a file by path in the event loop logs."""
+    block_async_io.enable()
+    with contextlib.suppress(FileNotFoundError):
+        open(path).close()
+
+    assert "Detected blocking call to open with args" in caplog.text