Added "getBySlug" method to Collections Service

refs https://github.com/TryGhost/Team/issues/3423

- This is a convenience method that should allow fetching collections by their slug. It is a great developer experience for in case when fetching built-in collections like "featured" and "index", so can avoid an extra call to find the collection and it's ide one wants to use.

ghost/collections/src/CollectionRepository.ts

@@ -1,6 +1,8 @@
 import {Collection} from './Collection';
+
 export interface CollectionRepository {
     save(collection: Collection): Promise<void>
     getById(id: string): Promise<Collection | null>
+    getBySlug(slug: string): Promise<Collection | null>
     getAll(options: any): Promise<Collection[]>
 }

ghost/collections/src/CollectionsRepositoryInMemory.ts

@@ -5,4 +5,8 @@ export class CollectionsRepositoryInMemory extends InMemoryRepository<string, Co
     protected toPrimitive(entity: Collection): object {
         return entity.toJSON();
     }
+
+    async getBySlug(slug: string): Promise<Collection | null> {
+        return this.store.find(item => item.slug === slug) || null;
+    }
 }

ghost/collections/src/CollectionsService.ts

@@ -228,6 +228,10 @@ export class CollectionsService {
         return await this.collectionsRepository.getById(id);
     }
 
+    async getBySlug(slug: string): Promise<Collection | null> {
+        return await this.collectionsRepository.getBySlug(slug);
+    }
+
     async getAll(options?: QueryOptions): Promise<{data: CollectionDTO[], meta: any}> {
         const collections = await this.collectionsRepository.getAll(options);
 

ghost/collections/test/collections.test.ts

@@ -49,18 +49,35 @@ describe('CollectionsService', function () {
         const createdCollection = await collectionsService.getById(savedCollection.id);
 
         assert.ok(createdCollection, 'Collection should be saved');
-        assert.ok(savedCollection.id, 'Collection should have an id');
+        assert.ok(createdCollection.id, 'Collection should have an id');
         assert.equal(createdCollection.title, 'testing collections', 'Collection title should match');
 
         const allCollections = await collectionsService.getAll();
         assert.equal(allCollections.data.length, 1, 'There should be one collection');
 
-        await collectionsService.destroy(savedCollection.id);
+        await collectionsService.destroy(createdCollection.id);
         const deletedCollection = await collectionsService.getById(savedCollection.id);
 
         assert.equal(deletedCollection, null, 'Collection should be deleted');
     });
 
+    it('Can retrieve a collection by slug', async function () {
+        const savedCollection = await collectionsService.createCollection({
+            title: 'slug test',
+            slug: 'get-me-by-slug',
+            type: 'manual',
+            filter: null
+        });
+
+        const retrievedCollection = await collectionsService.getBySlug('get-me-by-slug');
+        assert.ok(retrievedCollection, 'Collection should be saved');
+        assert.ok(retrievedCollection.slug, 'Collection should have a slug');
+        assert.equal(savedCollection.title, 'slug test', 'Collection title should match');
+
+        const nonExistingCollection = await collectionsService.getBySlug('i-do-not-exist');
+        assert.equal(nonExistingCollection, null, 'Collection should not exist');
+    });
+
     it('Throws when built in collection is attempted to be deleted', async function () {
         const collection = await collectionsService.createCollection({
             title: 'Featured Posts',

ghost/in-memory-repository/src/InMemoryRepository.ts

@@ -13,7 +13,7 @@ type Order<T> = {
 type OrderOption<T extends Entity<any>> = Order<T>[];
 
 export abstract class InMemoryRepository<IDType, T extends Entity<IDType>> {
-    private store: T[] = [];
+    protected store: T[] = [];
     private ids: Map<IDType, true> = new Map();
 
     constructor() {}