[api] Elide empty message construction in protobuf dispatch (#13871)

script/api_protobuf/api_protobuf.py

@@ -2270,10 +2270,13 @@ SOURCE_NAMES = {
     SOURCE_CLIENT: "SOURCE_CLIENT",
 }
 
-RECEIVE_CASES: dict[int, tuple[str, str | None]] = {}
+RECEIVE_CASES: dict[int, tuple[str, str | None, str]] = {}
 
 ifdefs: dict[str, str] = {}
 
+# Track messages with no fields (empty messages) for parameter elision
+EMPTY_MESSAGES: set[str] = set()
+
 
 def get_opt(
     desc: descriptor.DescriptorProto,
@@ -2504,26 +2507,26 @@ def build_service_message_type(
         # Only add ifdef when we're actually generating content
         if ifdef is not None:
             hout += f"#ifdef {ifdef}\n"
-        # Generate receive
+        # Generate receive handler and switch case
         func = f"on_{snake}"
-        hout += f"virtual void {func}(const {mt.name} &value){{}};\n"
-        case = ""
-        case += f"{mt.name} msg;\n"
-        # Check if this message has any fields (excluding deprecated ones)
         has_fields = any(not field.options.deprecated for field in mt.field)
-        if has_fields:
-            # Normal case: decode the message
+        is_empty = not has_fields
+        if is_empty:
+            EMPTY_MESSAGES.add(mt.name)
+        hout += f"virtual void {func}({'' if is_empty else f'const {mt.name} &value'}){{}};\n"
+        case = ""
+        if not is_empty:
+            case += f"{mt.name} msg;\n"
             case += "msg.decode(msg_data, msg_size);\n"
-        else:
-            # Empty message optimization: skip decode since there are no fields
-            case += "// Empty message: no decode needed\n"
         if log:
             case += "#ifdef HAS_PROTO_MESSAGE_DUMP\n"
-            case += f'this->log_receive_message_(LOG_STR("{func}"), msg);\n'
+            if is_empty:
+                case += f'this->log_receive_message_(LOG_STR("{func}"));\n'
+            else:
+                case += f'this->log_receive_message_(LOG_STR("{func}"), msg);\n'
             case += "#endif\n"
-        case += f"this->{func}(msg);\n"
+        case += f"this->{func}({'msg' if not is_empty else ''});\n"
         case += "break;"
-        # Store the message name and ifdef with the case for later use
         RECEIVE_CASES[id_] = (case, ifdef, mt.name)
 
         # Only close ifdef if we opened it
@@ -2839,6 +2842,7 @@ static const char *const TAG = "api.service";
     hpp += (
         "  void log_receive_message_(const LogString *name, const ProtoMessage &msg);\n"
     )
+    hpp += "  void log_receive_message_(const LogString *name);\n"
     hpp += " public:\n"
     hpp += "#endif\n\n"
 
@@ -2862,6 +2866,9 @@ static const char *const TAG = "api.service";
     cpp += "  DumpBuffer dump_buf;\n"
     cpp += '  ESP_LOGVV(TAG, "%s: %s", LOG_STR_ARG(name), msg.dump_to(dump_buf));\n'
     cpp += "}\n"
+    cpp += f"void {class_name}::log_receive_message_(const LogString *name) {{\n"
+    cpp += '  ESP_LOGVV(TAG, "%s: {}", LOG_STR_ARG(name));\n'
+    cpp += "}\n"
     cpp += "#endif\n\n"
 
     for mt in file.message_type:
@@ -2929,22 +2936,22 @@ static const char *const TAG = "api.service";
             hpp_protected += f"#ifdef {ifdef}\n"
             cpp += f"#ifdef {ifdef}\n"
 
-        hpp_protected += f"  void {on_func}(const {inp} &msg) override;\n"
+        is_empty = inp in EMPTY_MESSAGES
+        param = "" if is_empty else f"const {inp} &msg"
+        arg = "" if is_empty else "msg"
 
-        # For non-void methods, generate a send_ method instead of return-by-value
+        hpp_protected += f"  void {on_func}({param}) override;\n"
         if is_void:
-            hpp += f"  virtual void {func}(const {inp} &msg) = 0;\n"
+            hpp += f"  virtual void {func}({param}) = 0;\n"
         else:
-            hpp += f"  virtual bool send_{func}_response(const {inp} &msg) = 0;\n"
+            hpp += f"  virtual bool send_{func}_response({param}) = 0;\n"
 
-        cpp += f"void {class_name}::{on_func}(const {inp} &msg) {{\n"
-
-        # No authentication check here - it's done in read_message
+        cpp += f"void {class_name}::{on_func}({param}) {{\n"
         body = ""
         if is_void:
-            body += f"this->{func}(msg);\n"
+            body += f"this->{func}({arg});\n"
         else:
-            body += f"if (!this->send_{func}_response(msg)) {{\n"
+            body += f"if (!this->send_{func}_response({arg})) {{\n"
             body += "  this->on_fatal_error();\n"
             body += "}\n"