fix: honor UseReturnVariable when emitting call-action assignments

formatAction emitted `$Var = call microflow/nanoflow/java/javascript/external`
whenever the action's ResultVariableName/OutputVariableName was
non-empty, ignoring UseReturnVariable. Studio Pro stores the
variable name as a UI fallback even when UseReturnVariable=false
(the action discards its return), so re-exec of described MDL
introduced phantom output variable declarations.

Symptom: microflows with two call actions pointing at the same
sub-microflow/Java action, both with UseReturnVariable=false but
both carrying the same ResultVariableName, round-tripped as two
declarations of the same output variable, triggering CE0111
"Duplicate variable name" in Studio Pro.

Fix: emit the `$Var = ` prefix only when UseReturnVariable is true.
Applies to MicroflowCallAction, NanoflowCallAction, JavaActionCallAction,
JavaScriptActionCallAction, and CallExternalAction.

Existing tests that relied on the old behavior now set UseReturnVariable
explicitly — they were exercising the wrong BSON shape.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: hjothamendix

mdl/executor/cmd_javaactions_test.go

@@ -19,6 +19,7 @@ func TestFormatAction_JavaActionCall_EntityTypeParam(t *testing.T) {
 	action := &microflows.JavaActionCallAction{
 		JavaAction:         "MyModule.Validate",
 		ResultVariableName: "IsValid",
+		UseReturnVariable:  true,
 		ParameterMappings: []*microflows.JavaActionParameterMapping{
 			{
 				Parameter: "MyModule.Validate.InputObject",
@@ -40,6 +41,7 @@ func TestFormatAction_JavaActionCall_MixedParamTypes(t *testing.T) {
 	action := &microflows.JavaActionCallAction{
 		JavaAction:         "MyModule.ProcessEntity",
 		ResultVariableName: "Result",
+		UseReturnVariable:  true,
 		ParameterMappings: []*microflows.JavaActionParameterMapping{
 			{
 				Parameter: "MyModule.ProcessEntity.InputObject",
@@ -67,6 +69,7 @@ func TestFormatAction_JavaActionCall_EntityTypeParam_EmptyEntity(t *testing.T) {
 	action := &microflows.JavaActionCallAction{
 		JavaAction:         "MyModule.Validate",
 		ResultVariableName: "IsValid",
+		UseReturnVariable:  true,
 		ParameterMappings: []*microflows.JavaActionParameterMapping{
 			{
 				Parameter: "MyModule.Validate.InputObject",
@@ -280,6 +283,7 @@ func TestFormatAction_JavaActionCall_EntityTypeAndParameterizedParams(t *testing
 	action := &microflows.JavaActionCallAction{
 		JavaAction:         "MyModule.CopyAttributes",
 		ResultVariableName: "Result",
+		UseReturnVariable:  true,
 		ParameterMappings: []*microflows.JavaActionParameterMapping{
 			{
 				Parameter: "MyModule.CopyAttributes.EntityType",

mdl/executor/cmd_microflows_format_action.go

@@ -484,7 +484,7 @@ func formatAction(
 			paramStr = strings.Join(params, ", ")
 		}
 
-		if a.ResultVariableName != "" {
+		if a.UseReturnVariable && a.ResultVariableName != "" {
 			return fmt.Sprintf("$%s = call microflow %s(%s);", a.ResultVariableName, mfName, paramStr)
 		}
 		return fmt.Sprintf("call microflow %s(%s);", mfName, paramStr)
@@ -513,7 +513,7 @@ func formatAction(
 			paramStr = strings.Join(params, ", ")
 		}
 
-		if a.OutputVariableName != "" {
+		if a.UseReturnVariable && a.OutputVariableName != "" {
 			return fmt.Sprintf("$%s = call nanoflow %s(%s);", a.OutputVariableName, nfName, paramStr)
 		}
 		return fmt.Sprintf("call nanoflow %s(%s);", nfName, paramStr)
@@ -557,7 +557,7 @@ func formatAction(
 			paramStr = strings.Join(params, ", ")
 		}
 
-		if a.ResultVariableName != "" {
+		if a.UseReturnVariable && a.ResultVariableName != "" {
 			return fmt.Sprintf("$%s = call java action %s(%s);", a.ResultVariableName, javaActionName, paramStr)
 		}
 		return fmt.Sprintf("call java action %s(%s);", javaActionName, paramStr)
@@ -582,7 +582,7 @@ func formatAction(
 			paramStr = strings.Join(params, ", ")
 		}
 
-		if a.ResultVariableName != "" {
+		if a.UseReturnVariable && a.ResultVariableName != "" {
 			return fmt.Sprintf("$%s = call external action %s.%s(%s);", a.ResultVariableName, serviceName, actionName, paramStr)
 		}
 		return fmt.Sprintf("call external action %s.%s(%s);", serviceName, actionName, paramStr)
@@ -722,7 +722,7 @@ func formatAction(
 		return fmt.Sprintf("get workflow data $%s as %s;", a.WorkflowVariable, a.Workflow)
 
 	case *microflows.WorkflowCallAction:
-		if a.OutputVariableName != "" {
+		if a.UseReturnVariable && a.OutputVariableName != "" {
 			return fmt.Sprintf("$%s = call workflow %s ($%s);", a.OutputVariableName, a.Workflow, a.WorkflowContextVariable)
 		}
 		return fmt.Sprintf("call workflow %s ($%s);", a.Workflow, a.WorkflowContextVariable)
@@ -819,7 +819,7 @@ func formatAction(
 			paramStr = strings.Join(params, ", ")
 		}
 
-		if a.OutputVariableName != "" {
+		if a.UseReturnVariable && a.OutputVariableName != "" {
 			return fmt.Sprintf("$%s = call javascript action %s(%s);", a.OutputVariableName, jsActionName, paramStr)
 		}
 		return fmt.Sprintf("call javascript action %s(%s);", jsActionName, paramStr)

mdl/executor/cmd_microflows_format_action_test.go

@@ -341,6 +341,7 @@ func TestFormatAction_MicroflowCall_WithResult(t *testing.T) {
 	e := newTestExecutor()
 	action := &microflows.MicroflowCallAction{
 		ResultVariableName: "Result",
+		UseReturnVariable:  true,
 		MicroflowCall: &microflows.MicroflowCall{
 			Microflow: "MyModule.ProcessOrder",
 			ParameterMappings: []*microflows.MicroflowCallParameterMapping{
@@ -373,6 +374,7 @@ func TestFormatAction_JavaActionCall(t *testing.T) {
 	action := &microflows.JavaActionCallAction{
 		JavaAction:         "MyModule.SendEmail",
 		ResultVariableName: "Success",
+		UseReturnVariable:  true,
 		ParameterMappings: []*microflows.JavaActionParameterMapping{
 			{
 				Parameter: "MyModule.SendEmail.To",
@@ -395,6 +397,7 @@ func TestFormatAction_CallExternal(t *testing.T) {
 		ConsumedODataService: "MyModule.OrderService",
 		Name:                 "GetOrders",
 		ResultVariableName:   "Orders",
+		UseReturnVariable:    true,
 	}
 	got := e.formatAction(action, nil, nil)
 	want := "$Orders = call external action MyModule.OrderService.GetOrders();"
@@ -949,6 +952,7 @@ func TestFormatAction_JavaScriptActionCall_WithReturn(t *testing.T) {
 	action := &microflows.JavaScriptActionCallAction{
 		JavaScriptAction:   "MyModule.MyJSAction",
 		OutputVariableName: "Result",
+		UseReturnVariable:  true,
 	}
 	got := e.formatAction(action, nil, nil)
 	want := "$Result = call javascript action MyModule.MyJSAction();"
@@ -970,6 +974,7 @@ func TestFormatAction_JavaScriptActionCall_WithParams(t *testing.T) {
 			},
 		},
 		OutputVariableName: "Result",
+		UseReturnVariable:  true,
 	}
 	got := e.formatAction(action, nil, nil)
 	want := "$Result = call javascript action MyModule.MyJSAction(Input = $MyVar);"
@@ -1108,6 +1113,7 @@ func TestFormatAction_JavaScriptActionCall_WithOutputAndEmptyParam(t *testing.T)
 	action := &microflows.JavaScriptActionCallAction{
 		JavaScriptAction:   "MyModule.MyJSAction",
 		OutputVariableName: "Result",
+		UseReturnVariable:  true,
 		ParameterMappings: []*microflows.JavaScriptActionParameterMapping{
 			{
 				Parameter: "MyModule.MyJSAction.Input",