fix: write properties with defined default values on prototype

Author: NoNameProvided

src/TransformOperationExecutor.ts

@@ -170,9 +170,17 @@ export class TransformOperationExecutor {
                         if (metadata.options && metadata.options.discriminator && metadata.options.discriminator.property && metadata.options.discriminator.subTypes) {
                             if (!(value[valueKey] instanceof Array)) {
                                 if (this.transformationType === TransformationType.PLAIN_TO_CLASS) {
-                                    type = metadata.options.discriminator.subTypes.find((subType) => subType.name === subValue[metadata.options.discriminator.property]);
+                                    type = metadata.options.discriminator.subTypes.find((subType) => {
+                                        if (subValue && metadata.options.discriminator.property in subValue) {
+                                            return subType.name === subValue[metadata.options.discriminator.property]
+                                        }
+                                    });
                                     type === undefined ? type = newType : type = type.value;
-                                    if (!metadata.options.keepDiscriminatorProperty) delete subValue[metadata.options.discriminator.property];
+                                    if (!metadata.options.keepDiscriminatorProperty) {
+                                        if (subValue && metadata.options.discriminator.property in subValue) {
+                                            delete subValue[metadata.options.discriminator.property];
+                                        }
+                                    }
                                 }
                                 if (this.transformationType === TransformationType.CLASS_TO_CLASS) {
                                     type = subValue.constructor;
@@ -217,7 +225,7 @@ export class TransformOperationExecutor {
                 if (newValue.constructor.prototype) {
                     const descriptor = Object.getOwnPropertyDescriptor(newValue.constructor.prototype, newValueKey);
                     if ((this.transformationType === TransformationType.PLAIN_TO_CLASS || this.transformationType === TransformationType.CLASS_TO_CLASS)
-                        && ((descriptor && !descriptor.set) || newValue[newValueKey] instanceof Function)) //  || TransformationType === TransformationType.CLASS_TO_CLASS
+                        && ((descriptor && !descriptor.writable) || newValue[newValueKey] instanceof Function)) //  || TransformationType === TransformationType.CLASS_TO_CLASS
                         continue;
                 }
 

test/functional/serialization-deserialization.spec.ts

@@ -107,4 +107,46 @@ describe("serialization and deserialization objects", () => {
         // (<any>result).extra.should.be.undefined;
     });
 
-});
+
+    it("should not overwrite non writable properties on deserialize", () => {
+        class TestObject {
+            get getterOnlyProp(): string {
+                return "I cannot write!";
+            }
+
+            normalProp: string = "Hello!";
+        }
+
+        const payload = {
+            getterOnlyProp: "I CAN write!",
+            normalProp: "Goodbye!"
+        };
+
+        const result = deserialize(TestObject, JSON.stringify(payload));
+
+        result.getterOnlyProp.should.be.eql("I cannot write!");
+        result.normalProp.should.be.eql("Goodbye!");
+
+    });
+
+    it("should overwrite default properties defined in prototype", () => {
+        class TestObject {
+            normalProp: string = "Hello!";
+            prototypedProp: string;
+        }
+
+        TestObject.prototype.prototypedProp = "I'm a BUG!";
+
+
+        const payload = {
+            normalProp: "Goodbye!",
+            prototypedProp: "Goodbye!"
+        };
+
+        const result = deserialize(TestObject, JSON.stringify(payload));
+
+        result.normalProp.should.be.eql("Goodbye!");
+        result.prototypedProp.should.be.eql("Goodbye!");
+    });
+
+});