feat: sub-categories in sidebar.json (#892)

* Add ability to specify sub categories in sidebar.json

* move v1 files to correct place

* refactor implementation

* refactor naming for implementation clarity

v1/lib/server/__tests__/readMetadata.test.js

@@ -0,0 +1,77 @@
+/**
+ * Copyright (c) 2017-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+const {readSidebar} = require('../readMetadata');
+const sidebar = require('./__fixtures__/sidebar');
+const sidebarSubCategories = require('./__fixtures__/sidebar-subcategories');
+
+jest.mock('../env', () => ({
+  translation: {
+    enabled: true,
+    enabledLanguages: () => [
+      {
+        enabled: true,
+        name: 'English',
+        tag: 'en',
+      },
+      {
+        enabled: true,
+        name: '한국어',
+        tag: 'ko',
+      },
+    ],
+  },
+  versioning: {
+    enabled: true,
+    defaultVersion: '1.0.0',
+  },
+}));
+
+jest.mock(`${process.cwd()}/siteConfig.js`, () => true, {virtual: true});
+jest.mock(`${process.cwd()}/sidebar.json`, () => true, {virtual: true});
+
+describe('readMetadata', () => {
+  describe('readSidebar', () => {
+    it('should verify regular category data and verify sort', () => {
+      const order = readSidebar(sidebar);
+
+      // Put in this order to verify sort
+      ['doc1', 'doc2', 'doc4', 'doc3'].forEach((id, index) => {
+        expect(order[id]).toBeDefined();
+        expect(order[id].sort).toBe(index + 1);
+      });
+
+      expect(order.doc1.previous).toBeUndefined();
+      expect(order.doc2.previous).toBe('doc1');
+
+      expect(order.doc1.next).toBe('doc2');
+      expect(order.doc2.next).toBe('doc4');
+
+      expect(order.doc1.sub_category).toBeFalsy();
+    });
+
+    test('should verify sub category data and verify sort', () => {
+      const order = readSidebar(sidebarSubCategories);
+
+      // Put in this order to verify sort
+      ['doc2', 'doc1', 'doc3', 'doc5', 'doc4'].forEach((id, index) => {
+        expect(order[id]).toBeDefined();
+        expect(order[id].sort).toBe(index + 1);
+      });
+
+      expect(order.doc2.sidebar).toBe('docs');
+      expect(order.doc2.category).toBe('First Category');
+      expect(order.doc2.sub_category).toBe('Sub Cat One');
+
+      expect(order.doc1.category).toBe('First Category');
+      expect(order.doc1.sub_category).toBe('Sub Cat One');
+
+      expect(order.doc3.category).toBe('First Category');
+      expect(order.doc3.sub_category).toBe('Sub Cat Two');
+    });
+  });
+});