fix: skip field if nothing provided and default not set

Author: Velmisov

src/TransformOperationExecutor.ts

@@ -244,8 +244,11 @@ export class TransformOperationExecutor {
                         finalValue = this.transform(subSource, finalValue, type, arrayType, isSubValueMap, level + 1);
                     } else {
                         if (subValue === undefined) {
-                            // Set default value if nothing provided
-                            finalValue = newValue[newValueKey];
+                            const defaultValue = newValue[newValueKey];
+                            // Skip field if default value not set
+                            if (defaultValue === undefined) continue;
+                            // Set default value
+                            finalValue = defaultValue;
                         } else {
                             finalValue = this.transform(subSource, subValue, type, arrayType, isSubValueMap, level + 1);
                             finalValue = this.applyCustomTransformations(finalValue, (targetType as Function), transformKey, value, this.transformationType);

test/functional/basic-functionality.spec.ts

@@ -121,7 +121,7 @@ describe("basic functionality", () => {
         const transformedUser = plainToClass(User, fromPlainUser);
         transformedUser.should.be.instanceOf(User);
         transformedUser.should.have.property("age");
-        transformedUser.should.have.property("id").that.is.undefined;
+        transformedUser.should.not.have.property("id");
 
         const transformedUserWithoutExtra = plainToClass(User, fromPlainUser, { excludeExtraneousValues: true });
         transformedUserWithoutExtra.should.be.instanceOf(User);
@@ -1858,9 +1858,7 @@ describe("basic functionality", () => {
         transformedUser.should.be.instanceOf(User);
 
         transformedUser.should.be.eql({
-            age: undefined,
             ageWithDefault: 18,
-            firstName: undefined,
             firstNameWithDefault: "default first name",
             adminWithDefault: false,
             lastNameWithDefault: "default last name",