[light] Use const remove_reference_t<T> & to avoid copies of non-ref Ts

esphome/components/light/automation.h

@@ -37,14 +37,13 @@ template<bool HasTransitionLength, typename... Ts> class ToggleAction : public A
 // Trigger args are forwarded to the apply function so user lambdas
 // (e.g. `brightness: !lambda "return x;"`) keep working.
 //
-// Trigger args are forwarded as `Ts...`. The previous `const Ts &...`
+// Trigger args are forwarded as `const std::remove_reference_t<Ts> &...`
-// form caused codegen to emit `const T &` for each arg in the apply
+// (instead of `const Ts &...`) so codegen can emit the same form in the
-// lambda's parameter list, which is invalid C++ source text when T is
+// apply lambda's parameter list without producing `const T & &` for
-// already a reference (e.g. `const std::string & &` for triggers that
+// triggers whose Ts already carries a reference (e.g. `std::string &`).
-// pass `std::string &`).
 template<typename... Ts> class LightControlAction : public Action<Ts...> {
  public:
-  using ApplyFn = void (*)(LightState *, LightCall &, Ts...);
+  using ApplyFn = void (*)(LightState *, LightCall &, const std::remove_reference_t<Ts> &...);
   LightControlAction(LightState *parent, ApplyFn apply) : parent_(parent), apply_(apply) {}
 
   void play(const Ts &...x) override {

esphome/components/light/automation.py

@@ -230,15 +230,16 @@ async def light_control_to_code(config, action_id, template_arg, args):
                 f"call.set_effect(static_cast<uint32_t>({_resolve_effect_index(config)}));"
             )
 
-    # Forward trigger args as Ts... so each (type, name) pair passes through
+    # Match LightControlAction::ApplyFn signature: `const std::remove_reference_t<T> &`
-    # unchanged. Wrapping in `const &` here would emit invalid C++ source
+    # for each trigger arg so non-reference Ts stay no-copy (`const T &`) and
-    # for trigger types that already carry a reference (e.g. `std::string &`)
+    # reference Ts collapse correctly without producing `const T & &`.
-    # and fails on plain Python types (`float`/`bool`) which have no
-    # `.operator()` method.
     apply_args = [
         (LightState.operator("ptr"), "parent"),
         (LightCall.operator("ref"), "call"),
-        *args,
+        *(
+            (cg.RawExpression(f"const std::remove_reference_t<{cg.safe_exp(t)}> &"), n)
+            for t, n in args
+        ),
     ]
     apply_lambda = LambdaExpression(
         ["\n".join(body_lines)],