Check the lazy platform tables in a fresh interpreter instead of editing sys.modules

tests/unit_tests/components/test_logger.py

@@ -1,21 +1,16 @@
 """Tests for the logger component's lazy platform tables."""
 
+import subprocess
 import sys
 
+from esphome.components import logger
+
 
 def test_uart_selection_tables_exposed_for_external_tooling() -> None:
     """device-builder introspects these names off the module; keep them
-    accessible (and discoverable) without importing the platform packages."""
-    for mod in ("esphome.components.esp32", "esphome.components.libretiny"):
-        sys.modules.pop(mod, None)
-
-    from esphome.components import logger
-
+    accessible (and discoverable) and stable between accesses."""
     assert "UART_SELECTION_ESP32" in dir(logger)
     assert "UART_SELECTION_LIBRETINY" in dir(logger)
-    # dir() must not import the platform packages; only table access may
-    assert "esphome.components.esp32" not in sys.modules
-    assert "esphome.components.libretiny" not in sys.modules
     assert logger.UART_SELECTION_ESP32["ESP32C3"] == [
         "UART0",
         "UART1",
@@ -25,3 +20,18 @@ def test_uart_selection_tables_exposed_for_external_tooling() -> None:
     assert "bk72xx" in logger.UART_SELECTION_LIBRETINY
     # Repeated access returns the same cached object
     assert logger.UART_SELECTION_ESP32 is logger.UART_SELECTION_ESP32
+
+
+def test_dir_does_not_import_platform_packages() -> None:
+    """Listing the names must not load the platform packages; only reading a
+    table may. Checked in a fresh interpreter so nothing loaded by other tests
+    hides a leak, and nothing here changes what later tests see."""
+    check = (
+        "import sys; from esphome.components import logger; dir(logger); "
+        "print(','.join(m for m in ('esphome.components.esp32', "
+        "'esphome.components.libretiny') if m in sys.modules))"
+    )
+    result = subprocess.run(
+        [sys.executable, "-c", check], capture_output=True, text=True, check=True
+    )
+    assert result.stdout.strip() == ""