fix: better support for polymorphic inputs

src/classes/polymorphic-serialiser.ts

@@ -45,16 +45,48 @@ export default class PolymorphicSerializer<
         })
       );
 
-      return documents.reduce((result, document) => {
-        if (!result) {
-          return document;
-        }
+      // Construct initial document and included data
+      let document: Partial<DataDocument<PrimaryType>> = {
+        data: [],
+      };
+
+      // Document versioning
+      if (options?.version) {
+        document.jsonapi = { ...document.jsonapi, version: options.version };
+      }
 
+      if (options?.metaizers?.jsonapi) {
+        document.jsonapi = { ...document.jsonapi, meta: options.metaizers.jsonapi.metaize() };
+      }
+
+      document = documents.reduce((result, document) => {
         result.data = [result.data ?? [], document.data ?? []].flat();
         result.included = [result.included ?? [], document.included ?? []].flat();
 
         return result;
-      });
+      }, document);
+
+      // Handle meta
+      if (options?.metaizers?.document) {
+        document.meta = options.metaizers.document.metaize(data);
+      }
+
+      // Handle links
+      if (options?.linkers?.document) {
+        if (options.linkers.document) {
+          document.links = { ...document.links, self: options.linkers.document.link(data) };
+        }
+        if (options.linkers.paginator) {
+          const pagination = options.linkers.paginator.paginate(
+            data as PrimaryType | PrimaryType[]
+          );
+          if (pagination) {
+            document.links = { ...document.links, ...pagination };
+          }
+        }
+      }
+
+      return document;
     } else if (data) {
       return this.serializeType(data, options);
     }

test/issue-80.test.ts

@@ -76,4 +76,41 @@ describe('Issue #80 - Polymorphic serializer', () => {
     expect(data.data[0].id).toEqual('1');
     expect(data.data[0].type).toEqual('Model1');
   });
+
+  it('should correctly handle empty input', async () => {
+    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([])) as {
+      data: Resource<Model>;
+    };
+
+    expect(data.data).toBeInstanceOf(Array);
+    expect(data.data).toHaveLength(0);
+  });
+
+  it('should correctly handle non-array input', async () => {
+    const model1: Model1 = new Model1('1', 'model1');
+
+    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)) as {
+      data: Resource<Model>;
+    };
+
+    expect(data.data).toBeInstanceOf(Resource);
+    expect(data.data.id).toEqual('1');
+    expect(data.data.type).toEqual('Model1');
+  });
 });