fix: support excludeExtraneousValues option with ignoreDecorators enabled

Author: NoNameProvided

src/TransformOperationExecutor.ts

@@ -426,6 +426,16 @@ export class TransformOperationExecutor {
       return keys;
     }
 
+    /**
+     * If decorators are ignored but we don't want the extraneous values, then we use the
+     * metadata to decide which property is needed, but doesn't apply the decorator effect.
+     */
+    if (this.options.ignoreDecorators && this.options.excludeExtraneousValues && target) {
+      const exposedProperties = defaultMetadataStorage.getExposedProperties(target, this.transformationType);
+      const excludedProperties = defaultMetadataStorage.getExcludedProperties(target, this.transformationType);
+      keys = [...exposedProperties, ...excludedProperties];
+    }
+
     if (!this.options.ignoreDecorators && target) {
       // add all exposed to list of keys
       let exposedProperties = defaultMetadataStorage.getExposedProperties(target, this.transformationType);

src/interfaces/class-transformer-options.interface.ts

@@ -12,6 +12,9 @@ export interface ClassTransformOptions {
 
   /**
    * Indicates if extraneous properties should be excluded from the value when converting a plain value to a class.
+   *
+   * This option requires that each property on the target class has at least one `@Expose` or `@Exclude` decorator
+   * assigned from this library.
    */
   excludeExtraneousValues?: boolean;
 
@@ -33,8 +36,10 @@ export interface ClassTransformOptions {
   excludePrefixes?: string[];
 
   /**
-   * If set to true then class transformer will ignore all @Expose and @Exclude decorators and what inside them.
+   * If set to true then class transformer will ignore the effect of all @Expose and @Exclude decorators.
    * This option is useful if you want to kinda clone your object but do not apply decorators affects.
+   *
+   * __NOTE:__ You may still have to add the decorators to make other options work.
    */
   ignoreDecorators?: boolean;
 

test/functional/basic-functionality.spec.ts

@@ -118,6 +118,40 @@ describe('basic functionality', () => {
     expect(transformedUserWithoutExtra).not.toHaveProperty('age');
   });
 
+  it('should exclude extraneous values if both excludeExtraneousValues and ignoreDecorators option is set to true', () => {
+    // fixes https://github.com/typestack/class-transformer/issues/533
+    defaultMetadataStorage.clear();
+
+    class ExampleClass {
+      @Exclude()
+      public valueOne!: number;
+
+      @Expose()
+      public valueTwo!: number;
+    }
+
+    const transformationOptions = {
+      ignoreDecorators: true,
+      excludeExtraneousValues: true,
+    };
+
+    const instance = plainToClass(
+      ExampleClass,
+      { valueOne: 42, valueTwo: 42, extra: true, _otherExtra: true },
+      transformationOptions
+    );
+
+    expect(instance).toBeInstanceOf(ExampleClass);
+    expect(instance).toEqual({ valueOne: 42, valueTwo: 42 });
+
+    (instance as any).extraProp = 'not-needed';
+
+    expect(classToPlain(instance, transformationOptions)).toEqual({
+      valueOne: 42,
+      valueTwo: 42,
+    });
+  });
+
   it('should exclude all objects marked with @Exclude() decorator', () => {
     defaultMetadataStorage.clear();