Enable export and import of SDN configuration

resolves #269 (closed)

Related Issue

Motivation and Context

How Has This Been Tested?

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

controller/nucleus/southbound.go

@@ -122,42 +122,56 @@ func (oc *OpenConfig) Unmarshal(bytes []byte, path *gpb.Path, goStruct ygot.GoSt
 	return unmarshal(oc.Schema(), bytes, path, goStruct, opt...)
 }
 
-// unmarshal parses a gNMI response to a go struct.
-func unmarshal(schema *ytypes.Schema, bytes []byte, path *gpb.Path, goStruct ygot.GoStruct, opt ...ytypes.UnmarshalOpt) error {
-	defer func() {
-		if r := recover(); r != nil {
-			log.Error(r.(error))
-		}
-	}()
-
+// Generates an empty validated struct from a given schema and path
+func generateEmptyValidatedStructs(schema *ytypes.Schema, path *gpb.Path) (ygot.ValidatedGoStruct, ygot.ValidatedGoStruct, error) {
 	// Load SBI definition
 	root, err := ygot.DeepCopy(schema.Root)
 	if err != nil {
-		return err
+		return nil, nil, err
 	}
 	validatedDeepCopy, ok := root.(ygot.ValidatedGoStruct)
 	if !ok {
-		return &customerrs.InvalidTypeAssertionError{
+		return nil, nil, &customerrs.InvalidTypeAssertionError{
 			Value: root,
 			Type:  (*ygot.ValidatedGoStruct)(nil),
 		}
 	}
 
-	// returns the node we want to fill with the data contained in 'bytes',
-	// using the specified 'path'.
+	// returns the node we want to fill with the data contained in 'bytes', using the specified 'path'.
 	createdNode, _, err := ytypes.GetOrCreateNode(schema.RootSchema(), validatedDeepCopy, path)
 	if err != nil {
-		return err
+		return nil, nil, err
 	}
 	validatedCreatedNode, ok := createdNode.(ygot.ValidatedGoStruct)
 	if !ok {
-		return &customerrs.InvalidTypeAssertionError{
+		return nil, nil, &customerrs.InvalidTypeAssertionError{
 			Value: createdNode,
 			Type:  (*ygot.ValidatedGoStruct)(nil),
 		}
 	}
 
-	if err := openconfig.Unmarshal(bytes, validatedCreatedNode, opt...); err != nil {
+	return validatedDeepCopy, validatedCreatedNode, nil
+}
+
+// unmarshal parses a gNMI response to a go struct.
+func unmarshal(schema *ytypes.Schema, bytes []byte, path *gpb.Path, goStruct ygot.GoStruct, opt ...ytypes.UnmarshalOpt) error {
+	defer func() {
+		if r := recover(); r != nil {
+			log.Error(r.(error))
+		}
+	}()
+
+	validatedDeepCopy, emptyValidatedCreatedNode, err := generateEmptyValidatedStructs(schema, path)
+	if err != nil {
+		return err
+	}
+
+	_, emptyValidatedCreatedNodeForDiff, err := generateEmptyValidatedStructs(schema, path)
+	if err != nil {
+		return err
+	}
+
+	if err := openconfig.Unmarshal(bytes, emptyValidatedCreatedNode, opt...); err != nil {
 		return err
 	}