feat: serialize polymorphic documents

Author: egmacke

src/classes/polymorphic-serialiser.ts

@@ -29,8 +29,21 @@ export default class PolymorphicSerializer<
     options?: Partial<SerializerOptions<PrimaryType>>
   ): Promise<Partial<DataDocument<PrimaryType>>> {
     if (Array.isArray(data)) {
-      data.map((d) => {
-        return this.serializeSingle(d, options);
+      const documents = await Promise.all(
+        data.map((d) => {
+          return this.serializeSingle(d, options);
+        })
+      );
+
+      return documents.reduce((result, document) => {
+        if (!result) {
+          return document;
+        }
+
+        result.data = [result.data ?? [], document.data ?? []].flat();
+        result.included = [result.included ?? [], document.included ?? []].flat();
+
+        return result;
       });
     } else if (data) {
       return this.serializeSingle(data, options);

test/issue-80.test.ts

@@ -0,0 +1,58 @@
+import { PolymorphicSerializer, Serializer } from '../lib';
+import Resource from '../lib/models/resource.model';
+
+describe('Issue #80 - Polymorphic serializer', () => {
+  abstract class Model {
+    public type: string;
+
+    constructor(public id: string) {}
+  }
+
+  class Model1 extends Model {
+    constructor(id: string, public model1: string) {
+      super(id);
+      this.type = 'type:Model1';
+    }
+  }
+
+  class Model2 extends Model {
+    constructor(id: string, public model2: string) {
+      super(id);
+      this.type = 'type:Model2';
+    }
+  }
+
+  class Model3 extends Model {
+    constructor(id: string, public model2: string) {
+      super(id);
+      this.type = 'type:Model3';
+    }
+  }
+
+  it('should work polymorphicly', async () => {
+    const model1: Model1 = new Model1('1', 'model1');
+    const model2: Model2 = new Model2('2', 'model2');
+    const model3: Model3 = new Model3('3', 'model3');
+
+    const Model1Serializer = new Serializer<Model1>('Model1');
+    const Model2Serializer = new Serializer<Model2>('Model2');
+
+    const PolySerializer = new PolymorphicSerializer<Model>('Model', 'type', {
+      'type:Model1': Model1Serializer,
+      'type:Model2': Model2Serializer,
+    });
+
+    const data = (await PolySerializer.serialize([model1, model2, model3])) as {
+      data: Resource<Model>;
+    };
+
+    expect(data.data).toBeInstanceOf(Array);
+    expect(data.data).toHaveLength(3);
+    expect(data.data[0].id).toEqual('1');
+    expect(data.data[0].type).toEqual('Model1');
+    expect(data.data[1].id).toEqual('2');
+    expect(data.data[1].type).toEqual('Model2');
+    expect(data.data[2].id).toEqual('3');
+    expect(data.data[2].type).toEqual('Model');
+  });
+});