Expose lazy UART tables in dir() and pin the contract with a test

esphome/components/logger/__init__.py

@@ -1,3 +1,4 @@
+import functools
 import re
 
 from esphome import automation
@@ -112,6 +113,7 @@ HARDWARE_UART_TO_SERIAL = {
 is_log_level = cv.one_of(*LOG_LEVELS, upper=True)
 
 
+@functools.cache
 def _uart_selection_esp32() -> dict[str, list[str]]:
     from esphome.components.esp32 import (
         VARIANT_ESP32,
@@ -146,6 +148,7 @@ def _uart_selection_esp32() -> dict[str, list[str]]:
     }
 
 
+@functools.cache
 def _uart_selection_libretiny() -> dict[str, list[str]]:
     from esphome.components.libretiny.const import (
         COMPONENT_BK72XX,
@@ -160,16 +163,24 @@ def _uart_selection_libretiny() -> dict[str, list[str]]:
     }
 
 
-def __getattr__(name: str):
-    # These tables are introspected by external tooling (esphome/device-builder);
-    # built on access so the platform packages stay out of module import.
-    if name == "UART_SELECTION_ESP32":
-        return _uart_selection_esp32()
-    if name == "UART_SELECTION_LIBRETINY":
-        return _uart_selection_libretiny()
+# These tables are introspected by external tooling (esphome/device-builder);
+# built on access so the platform packages stay out of module import.
+_LAZY_UART_SELECTION_TABLES = {
+    "UART_SELECTION_ESP32": _uart_selection_esp32,
+    "UART_SELECTION_LIBRETINY": _uart_selection_libretiny,
+}
+
+
+def __getattr__(name: str) -> dict[str, list[str]]:
+    if (table := _LAZY_UART_SELECTION_TABLES.get(name)) is not None:
+        return table()
     raise AttributeError(f"module {__name__!r} has no attribute {name!r}")
 
 
+def __dir__() -> list[str]:
+    return [*globals(), *_LAZY_UART_SELECTION_TABLES]
+
+
 def uart_selection(value):
     if CORE.is_esp32:
         from esphome.components.esp32 import get_esp32_variant

tests/unit_tests/components/test_logger.py

@@ -0,0 +1,24 @@
+"""Tests for the logger component's lazy platform tables."""
+
+import sys
+
+
+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
+
+    assert "UART_SELECTION_ESP32" in dir(logger)
+    assert "UART_SELECTION_LIBRETINY" in dir(logger)
+    assert logger.UART_SELECTION_ESP32["ESP32C3"] == [
+        "UART0",
+        "UART1",
+        "USB_CDC",
+        "USB_SERIAL_JTAG",
+    ]
+    assert "bk72xx" in logger.UART_SELECTION_LIBRETINY
+    # Repeated access returns the same cached object
+    assert logger.UART_SELECTION_ESP32 is logger.UART_SELECTION_ESP32