fix: add missing emptiness-check

Author: Strobotti

README.md

@@ -1,5 +1,9 @@
 # JSON:API deserializer in Typescript
 
+A JSON:API response payload is a normalized set of entities and their relationships plus some metadata. This package
+deserializes a JSON:API response payload into an object graph, using user-defined entity deserializers to build the
+actual entities.
+
 ## Installation
 
 ```shell
@@ -14,7 +18,7 @@ This example uses the jsonapi.org sample data (added the missing person, though)
 
 ```typescript
 // Import the package and required interfaces:
-import {Item, ItemDeserializer, RelationshipDeserializer} from "jsonapi-ts-deserializer";
+import {getDeserializer, Item, ItemDeserializer, RelationshipDeserializer} from "jsonapi-ts-deserializer";
 
 // Have some data to deserialize:
 const jsonapiOrgExampleData = {

src/__tests__/Deserializer.test.ts

@@ -166,6 +166,119 @@ class CommentDeserializer implements ItemDeserializer {
   }
 }
 
+// a JSON:API response with a simple directory structure with a couple of files and folders
+const fileSystemExampleData = {
+  data: [
+    {
+      type: 'folders',
+      id: '1',
+      attributes: {
+        name: 'root',
+      },
+      relationships: {
+        children: {
+          data: [
+            {
+              type: 'folders',
+              id: '2',
+            },
+            {
+              type: 'files',
+              id: '3',
+            },
+          ],
+        },
+      },
+    }
+  ],
+  included: [
+    {
+      type: 'folders',
+      id: '2',
+      attributes: {
+        name: 'home',
+      },
+      relationships: {
+        children: {
+          data: [
+            {
+              type: 'files',
+              id: '4',
+            },
+            {
+              type: 'folders',
+              id: '5',
+            }
+          ],
+        },
+      },
+    },
+    {
+      type: 'files',
+      id: '3',
+      attributes: {
+        name: 'swapfile',
+      },
+    },
+    {
+      type: 'files',
+      id: '4',
+      attributes: {
+        name: 'README.md',
+      },
+    },
+    {
+      type: 'folders',
+      id: '5',
+      attributes: {
+        name: 'juha',
+      }
+    }
+  ]
+}
+
+type Folder = {
+    id: number;
+    name: string;
+    children: (Folder | File)[];
+}
+
+type File = {
+    id: number;
+    name: string;
+}
+
+class FolderDeserializer implements ItemDeserializer {
+    getType(): string {
+        return 'folders';
+    }
+
+    deserialize(item: Item, relationshipDeserializer: RelationshipDeserializer): any {
+        const folder: Folder = {
+            id: parseInt(item.id),
+            name: item.attributes.name,
+            children: [],
+        };
+
+        folder.children = relationshipDeserializer.deserializeRelationships(relationshipDeserializer, item, 'children');
+
+        return folder;
+    }
+}
+
+class FileDeserializer implements ItemDeserializer {
+    getType(): string {
+        return 'files';
+    }
+
+    deserialize(item: Item, relationshipDeserializer: RelationshipDeserializer): any {
+        return {
+            id: parseInt(item.id),
+            name: item.attributes.name,
+        };
+    }
+}
+
 describe('Deserializer', () => {
   it('deserializes the jsonapi.org example into an object graph', () => {
     const deserializer = getDeserializer([
@@ -178,4 +291,15 @@ describe('Deserializer', () => {
 
     expect(rootItems).toMatchSnapshot();
   });
-});
+
+  it('deserializes a file system example into an object graph', () => {
+    const deserializer = getDeserializer([
+        new FolderDeserializer(),
+        new FileDeserializer(),
+    ]);
+
+    const rootItems: any[] = deserializer.consume(fileSystemExampleData).getRootItems();
+
+    expect(rootItems).toMatchSnapshot();
+  });
+})

src/__tests__/__snapshots__/Deserializer.test.ts.snap

@@ -1,5 +1,35 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
+exports[`Deserializer deserializes a file system example into an object graph 1`] = `
+[
+  {
+    "children": [
+      {
+        "children": [
+          {
+            "id": 4,
+            "name": "README.md",
+          },
+          {
+            "children": [],
+            "id": 5,
+            "name": "juha",
+          },
+        ],
+        "id": 2,
+        "name": "home",
+      },
+      {
+        "id": 3,
+        "name": "swapfile",
+      },
+    ],
+    "id": 1,
+    "name": "root",
+  },
+]
+`;
+
 exports[`Deserializer deserializes the jsonapi.org example into an object graph 1`] = `
 [
   {

src/index.ts

@@ -108,8 +108,9 @@ export class Deserializer implements RelationshipDeserializer {
   }
 
   deserializeRelationships(relationshipDeserializer: RelationshipDeserializer, item: Item, name: string): any[] {
-    const relationships = item.relationships[name].data;
+    if (!item?.relationships || !item.relationships[name]) return [];
 
+    const relationships = item.relationships[name].data;
     const ret: any[] = [];
 
     relationships.forEach((relationship: any) => {