[core][select] Pass the select.set option as a plain literal (#19568)

tests/unit_tests/test_automation.py

@@ -18,6 +18,7 @@ from esphome.automation import (
     TriggerOnTrueForwarder,
     build_callback_automations,
     has_non_synchronous_actions,
+    literal_with_length,
     maybe_simple_id,
     register_apply_action,
     register_apply_condition,
@@ -838,6 +839,23 @@ async def test_apply_string_constant_stays_in_flash_on_esp8266(
     )
 
 
+@pytest.mark.asyncio
+@pytest.mark.parametrize("platform", ["esp32", "esp8266"])
+async def test_apply_literal_with_length_is_plain_on_every_platform(
+    registries: tuple[Registry, Registry], mock_cg: MockCodegen, platform: str
+) -> None:
+    """A (const char *, size_t) target gets the RAM literal and its byte length, never a flash copy."""
+    fields = (
+        ApplyField("option", "set_option", cg.std_string, const_fn=literal_with_length),
+    )
+    await _run_apply_action(
+        registries, fields, {"option": "h\u00e9llo"}, platform=platform
+    )
+    text = _apply_lambda(mock_cg)
+    assert f'::{PARENT_OBJ}->set_option("h\\303\\251llo", 6);' in text
+    assert "progmem_string" not in text
+
+
 @pytest.mark.asyncio
 async def test_register_apply_condition_predicate(
     registries: tuple[Registry, Registry], mock_cg: MockCodegen