Add as_function to allow macros to return values (#142033)

tests/helpers/test_template.py

@@ -828,6 +828,23 @@ def test_apply_macro_with_arguments(hass: HomeAssistant) -> None:
     ).async_render() == ["Hey, Alice!", "Hey, Bob!"]
 
 
+def test_as_function(hass: HomeAssistant) -> None:
+    """Test as_function."""
+    assert (
+        template.Template(
+            """
+            {%- macro macro_double(num, returns) -%}
+            {%- do returns(num * 2) -%}
+            {%- endmacro -%}
+            {%- set double = macro_double | as_function -%}
+            {{ double(5) }}
+            """,
+            hass,
+        ).async_render()
+        == 10
+    )
+
+
 def test_logarithm(hass: HomeAssistant) -> None:
     """Test logarithm."""
     tests = [