[light] Keep the effect list in a flash table (#20204)

Co-authored-by: pre-commit-ci-lite[bot] <117423508+pre-commit-ci-lite[bot]@users.noreply.github.com>

tests/component_tests/light/test_default_setters.py

@@ -2,6 +2,14 @@
 
 from collections.abc import Callable
 from pathlib import Path
+import re
+
+import pytest
+
+import esphome.codegen as cg
+from esphome.components import light
+from esphome.components.light import types as light_types
+from esphome.core import ID, EsphomeError
 
 
 def test_default_flash_length_and_empty_effects_are_not_emitted(
@@ -16,4 +24,20 @@ def test_default_flash_length_and_empty_effects_are_not_emitted(
     assert "bare_light->set_flash_transition_length(" not in main_cpp
     assert "bare_light->add_effects(" not in main_cpp
     assert "fancy_light->set_flash_transition_length(500);" in main_cpp
-    assert "fancy_light->add_effects({" in main_cpp
+    call = re.search(r"fancy_light->add_effects\((\w+), (\d+)\);", main_cpp)
+    assert call is not None
+    # The effect pointers form a flash table; they are address constants, not constexpr
+    assert re.search(
+        rf"static light::LightEffect \* const {call.group(1)}\[\] PROGMEM = \{{[^}}]+\}};",
+        main_cpp,
+    )
+
+
+def test_effect_assigned_in_setup_is_rejected() -> None:
+    """A pointer assigned in setup() would make the flash table need dynamic init."""
+    dynamic_effect = cg.Pvariable(
+        ID("dynamic_effect", is_declaration=True, type=light_types.LightEffect),
+        cg.RawExpression("make_effect()"),
+    )
+    with pytest.raises(EsphomeError, match="dynamic_effect"):
+        light._effects_table([dynamic_effect])