[lvgl] Memoize and lazily build container_schema (#16567)

esphome/components/lvgl/schemas.py

@@ -1,4 +1,5 @@
 from collections.abc import Callable
+from typing import Any
 
 from esphome import config_validation as cv
 from esphome.automation import Trigger, validate_automation
@@ -534,7 +535,16 @@ def strip_defaults(schema: cv.Schema):
     return cv.Schema({cv.Optional(k): v for k, v in schema.schema.items()})
 
 
-def container_schema(widget_type: WidgetType, extras=None):
+# Keyed by (id(widget_type), id(extras)); strong refs in the value keep both
+# alive so id() can't be recycled.
+_CONTAINER_SCHEMA_CACHE: dict[
+    tuple[int, int], tuple[Any, Any, Callable[[Any], Any]]
+] = {}
+
+
+def container_schema(
+    widget_type: WidgetType, extras: Any = None
+) -> Callable[[Any], Any]:
     """
     Create a schema for a container widget of a given type. All obj properties are available, plus
     the extras passed in, plus any defined for the specific widget being specified.
@@ -542,19 +552,31 @@ def container_schema(widget_type: WidgetType, extras=None):
     :param extras:  Additional options to be made available, e.g. layout properties for children
     :return: The schema for this type of widget.
     """
-    schema = obj_schema(widget_type).extend(
-        {cv.GenerateID(): cv.declare_id(widget_type.w_type)}
-    )
-    if extras:
-        schema = schema.extend(extras)
-    # Delayed evaluation for recursion
+    cache_key = (id(widget_type), id(extras))
+    cached = _CONTAINER_SCHEMA_CACHE.get(cache_key)
+    if cached is not None:
+        cached_widget_type, cached_extras, cached_validator = cached
+        if cached_widget_type is widget_type and cached_extras is extras:
+            return cached_validator
 
-    schema = schema.extend(widget_type.schema)
+    cached_schema: cv.Schema | None = None
 
-    def validator(value):
+    def get_schema() -> cv.Schema:
+        nonlocal cached_schema
+        if cached_schema is None:
+            schema = obj_schema(widget_type).extend(
+                {cv.GenerateID(): cv.declare_id(widget_type.w_type)}
+            )
+            if extras:
+                schema = schema.extend(extras)
+            cached_schema = schema.extend(widget_type.schema)
+        return cached_schema
+
+    def validator(value: Any) -> Any:
         value = value or {}
-        return append_layout_schema(schema, value)(value)
+        return append_layout_schema(get_schema(), value)(value)
 
+    _CONTAINER_SCHEMA_CACHE[cache_key] = (widget_type, extras, validator)
     return validator
 
 

tests/component_tests/lvgl/test_container_schema_cache.py

@@ -0,0 +1,87 @@
+"""Tests for container_schema() memoization and lazy build."""
+
+from __future__ import annotations
+
+from collections.abc import Generator
+from unittest.mock import patch
+
+import pytest
+
+from esphome import config_validation as cv
+import esphome.components.lvgl  # noqa: F401
+from esphome.components.lvgl import schemas as lvgl_schemas
+from esphome.components.lvgl.schemas import WIDGET_TYPES, container_schema
+
+
+@pytest.fixture(autouse=True)
+def _clear_container_schema_cache() -> Generator[None]:
+    cache = getattr(lvgl_schemas, "_CONTAINER_SCHEMA_CACHE", None)
+    if cache is not None:
+        cache.clear()
+    yield
+    if cache is not None:
+        cache.clear()
+
+
+def _widget_type(name: str = "obj"):
+    wt = WIDGET_TYPES.get(name)
+    assert wt is not None, f"widget type {name!r} not registered"
+    return wt
+
+
+def test_same_args_return_same_validator() -> None:
+    wt = _widget_type("obj")
+    assert container_schema(wt) is container_schema(wt)
+
+
+def test_extras_none_vs_truthy_get_different_validators() -> None:
+    wt = _widget_type("obj")
+    no_extras = container_schema(wt)
+    extras = {cv.Optional("custom_extra"): cv.string}
+    assert no_extras is not container_schema(wt, extras)
+
+
+def test_different_widget_types_get_different_validators() -> None:
+    assert container_schema(_widget_type("obj")) is not container_schema(
+        _widget_type("label")
+    )
+
+
+def test_schema_build_is_deferred_until_first_validation() -> None:
+    wt = _widget_type("obj")
+    with patch.object(
+        lvgl_schemas, "obj_schema", wraps=lvgl_schemas.obj_schema
+    ) as obj_schema_mock:
+        validator = container_schema(wt)
+        assert obj_schema_mock.call_count == 0
+        validator({})
+        assert obj_schema_mock.call_count == 1
+        validator({})
+        assert obj_schema_mock.call_count == 1
+
+
+def test_cached_validator_produces_equivalent_output() -> None:
+    wt = _widget_type("obj")
+    cached = container_schema(wt)
+    cached_result = cached({})
+    lvgl_schemas._CONTAINER_SCHEMA_CACHE.clear()
+    reference = container_schema(wt)
+    assert cached is not reference
+    assert cached_result == reference({})
+
+
+def test_id_recycling_is_caught_by_identity_guard() -> None:
+    wt = _widget_type("obj")
+    real_extras = {cv.Optional("a"): cv.int_}
+    validator_a = container_schema(wt, real_extras)
+
+    cache_key = (id(wt), id(real_extras))
+    cached_entry = lvgl_schemas._CONTAINER_SCHEMA_CACHE[cache_key]
+    sentinel = {cv.Optional("a"): cv.int_}
+    lvgl_schemas._CONTAINER_SCHEMA_CACHE[cache_key] = (
+        cached_entry[0],
+        sentinel,
+        cached_entry[2],
+    )
+
+    assert container_schema(wt, real_extras) is not validator_a