From 67f26b6cf77bbcdb4feba5f600b301167ecc8964 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Tue, 7 Apr 2026 22:46:31 -1000
Subject: [PATCH] fix 8266 flash string opt

---
 esphome/components/globals/__init__.py |  2 +-
 esphome/cpp_generator.py               |  7 ++++---
 tests/unit_tests/test_cpp_generator.py | 16 +++++++---------
 3 files changed, 12 insertions(+), 13 deletions(-)

diff --git a/esphome/components/globals/__init__.py b/esphome/components/globals/__init__.py
index fe83b1ea7c..ec6730a41c 100644
--- a/esphome/components/globals/__init__.py
+++ b/esphome/components/globals/__init__.py
@@ -109,7 +109,7 @@ async def globals_set_to_code(config, action_id, template_arg, args):
     template_arg = cg.TemplateArguments(full_id.type, *template_arg)
     var = cg.new_Pvariable(action_id, template_arg, paren)
     templ = await cg.templatable(
-        config[CONF_VALUE], args, None, to_exp=cg.RawExpression
+        config[CONF_VALUE], args, None, to_exp=cg.RawExpression, wrap_constant=True
     )
     cg.add(var.set_value(templ))
     return var
diff --git a/esphome/cpp_generator.py b/esphome/cpp_generator.py
index 814e37e02c..cf90b878e1 100644
--- a/esphome/cpp_generator.py
+++ b/esphome/cpp_generator.py
@@ -819,6 +819,8 @@ async def templatable(
     args: list[tuple[SafeExpType, str]],
     output_type: SafeExpType | None,
     to_exp: Callable | dict = None,
+    *,
+    wrap_constant: bool = False,
 ):
     """Generate code for a templatable config option.
 
@@ -850,9 +852,8 @@ async def templatable(
         return FlashStringLiteral(value)
     # Wrap non-string constants in stateless lambdas so that TemplatableFn
     # (used by TEMPLATABLE_VALUE macro) stores them as function pointers.
-    # When output_type is None, the lambda omits the return type annotation
-    # and the C++ compiler deduces it (used by globals where T is unknown).
-    if output_type is not std_string:
+    # wrap_constant=True forces wrapping even with output_type=None (compiler deduces type).
+    if (output_type is not None or wrap_constant) and output_type is not std_string:
         return LambdaExpression(
             f"return {safe_exp(value)};",
             args,
diff --git a/tests/unit_tests/test_cpp_generator.py b/tests/unit_tests/test_cpp_generator.py
index c75851df0c..81ae586e23 100644
--- a/tests/unit_tests/test_cpp_generator.py
+++ b/tests/unit_tests/test_cpp_generator.py
@@ -652,11 +652,11 @@ async def test_templatable__empty_string_with_std_string() -> None:
 
 @pytest.mark.asyncio
 async def test_templatable__string_with_none_output_type() -> None:
-    """Static string with output_type=None returns stateless lambda (no return type)."""
+    """Static string with output_type=None returns raw string (no wrapping)."""
     result = await cg.templatable("hello", [], None)
 
-    assert isinstance(result, cg.LambdaExpression)
-    assert result.capture == ""
+    assert isinstance(result, str)
+    assert result == "hello"
 
 
 @pytest.mark.asyncio
@@ -678,11 +678,10 @@ async def test_templatable__string_with_non_string_output_type() -> None:
 
 @pytest.mark.asyncio
 async def test_templatable__with_to_exp_callable() -> None:
-    """When to_exp is provided with output_type=None, result is lambda-wrapped."""
+    """When to_exp is provided, it is applied to non-template values."""
     result = await cg.templatable(42, [], None, to_exp=lambda x: x * 2)
 
-    assert isinstance(result, cg.LambdaExpression)
-    assert result.capture == ""
+    assert result == 84
 
 
 @pytest.mark.asyncio
@@ -696,12 +695,11 @@ async def test_templatable__with_to_exp_callable_and_output_type() -> None:
 
 @pytest.mark.asyncio
 async def test_templatable__with_to_exp_dict() -> None:
-    """When to_exp is a dict, value is looked up and lambda-wrapped."""
+    """When to_exp is a dict, value is looked up."""
     mapping: dict[str, int] = {"on": 1, "off": 0}
     result = await cg.templatable("on", [], None, to_exp=mapping)
 
-    assert isinstance(result, cg.LambdaExpression)
-    assert result.capture == ""
+    assert result == 1
 
 
 @pytest.mark.asyncio