fix: harden multi-arg adapter handling and centralize data type fallback

Co-authored-by: sawka <2722291+sawka@users.noreply.github.com>

Author: Copilot

pkg/gogen/gogen.go

@@ -107,10 +107,7 @@ func GenMethod_ResponseStream(buf *strings.Builder, methodDecl *wshrpc.WshRpcMet
 }
 
 func getWshMethodDataParamsAndExpr(methodDecl *wshrpc.WshRpcMethodDecl) (string, string) {
-	dataTypes := methodDecl.CommandDataTypes
-	if len(dataTypes) == 0 && methodDecl.CommandDataType != nil {
-		dataTypes = []reflect.Type{methodDecl.CommandDataType}
-	}
+	dataTypes := methodDecl.GetCommandDataTypes()
 	if len(dataTypes) == 0 {
 		return "", "nil"
 	}

pkg/tsgen/tsgen.go

@@ -497,10 +497,7 @@ func generateWshClientApiMethod_Call(methodDecl *wshrpc.WshRpcMethodDecl, tsType
 }
 
 func getTsWshMethodDataParamsAndExpr(methodDecl *wshrpc.WshRpcMethodDecl, tsTypesMap map[reflect.Type]string) (string, string) {
-	dataTypes := methodDecl.CommandDataTypes
-	if len(dataTypes) == 0 && methodDecl.CommandDataType != nil {
-		dataTypes = []reflect.Type{methodDecl.CommandDataType}
-	}
+	dataTypes := methodDecl.GetCommandDataTypes()
 	if len(dataTypes) == 0 {
 		return "", "null"
 	}

pkg/wshrpc/wshrpcmeta.go

@@ -20,6 +20,16 @@ type WshRpcMethodDecl struct {
 	DefaultResponseDataType reflect.Type
 }
 
+func (decl *WshRpcMethodDecl) GetCommandDataTypes() []reflect.Type {
+	if len(decl.CommandDataTypes) > 0 {
+		return decl.CommandDataTypes
+	}
+	if decl.CommandDataType != nil {
+		return []reflect.Type{decl.CommandDataType}
+	}
+	return nil
+}
+
 var contextRType = reflect.TypeOf((*context.Context)(nil)).Elem()
 var wshRpcInterfaceRType = reflect.TypeOf((*WshRpcInterface)(nil)).Elem()
 

pkg/wshrpc/wshrpcmeta_test.go

@@ -34,4 +34,7 @@ func TestGenerateWshCommandDecl_MultiArgs(t *testing.T) {
 	if decl.CommandDataType == nil || decl.CommandDataType.Kind() != reflect.String {
 		t.Fatalf("expected legacy single data type to remain first arg type, got %v", decl.CommandDataType)
 	}
+	if len(decl.GetCommandDataTypes()) != 2 {
+		t.Fatalf("expected helper to return two command data types")
+	}
 }

pkg/wshutil/wshadapter.go

@@ -100,10 +100,7 @@ func serverImplAdapter(impl any) func(*RpcResponseHandler) bool {
 		implMethod := reflect.ValueOf(impl).MethodByName(rmethod.Name)
 		var callParams []reflect.Value
 		callParams = append(callParams, reflect.ValueOf(handler.Context()))
-		commandDataTypes := methodDecl.CommandDataTypes
-		if len(commandDataTypes) == 0 && methodDecl.CommandDataType != nil {
-			commandDataTypes = []reflect.Type{methodDecl.CommandDataType}
-		}
+		commandDataTypes := methodDecl.GetCommandDataTypes()
 		if len(commandDataTypes) == 1 {
 			cmdData, err := recodeCommandData(cmd, handler.GetCommandRawData(), commandDataTypes[0])
 			if err != nil {
@@ -117,7 +114,11 @@ func serverImplAdapter(impl any) func(*RpcResponseHandler) bool {
 				handler.SendResponseError(err)
 				return true
 			}
-			multiArg := multiArgAny.(wshrpc.MultiArg)
+			multiArg, ok := multiArgAny.(wshrpc.MultiArg)
+			if !ok {
+				handler.SendResponseError(fmt.Errorf("command %q invalid multi arg payload", cmd))
+				return true
+			}
 			if len(multiArg.Args) != len(commandDataTypes) {
 				handler.SendResponseError(fmt.Errorf("command %q expected %d args, got %d", cmd, len(commandDataTypes), len(multiArg.Args)))
 				return true