feat: implement auto EagerLoads in library (#506)

README.md

@@ -261,6 +261,46 @@ const paginateConfig: PaginateConfig<CatEntity> {
 }
 ```
 
+## Eager loading
+
+Eager loading should work with typeorm's eager property out the box. Like so
+
+```typescript
+import { Entity, OneToMany } from 'typeorm';
+
+@Entity()
+export class CatEntity {
+  @PrimaryGeneratedColumn()
+  id: number
+
+  @Column('text')
+  name: string
+
+  @Column('text')
+  color: string
+
+  @Column('int')
+  age: number
+
+  @OneToMany(() => CatToyEntity, (catToy) => catToy.cat, {
+    eager: true,
+  })
+  toys: CatToyEntity[]
+}
+
+// service
+class CatService {
+  constructor(private readonly catsRepository: Repository<CatEntity>) {}
+
+  public findAll(query: PaginateQuery): Promise<Paginated<CatEntity>> {
+    return paginate(query, this.catsRepository, {
+      sortableColumns: ['id', 'name', 'color', 'age'],
+      loadEagerRelations: true // set this property as true to enable the eager loading
+    })
+  }
+}
+```
+
 ## Usage with Query Builder
 
 You can paginate custom queries by passing on the query builder:

src/__tests__/cat.entity.ts

@@ -32,7 +32,9 @@ export class CatEntity {
     @Column(() => SizeEmbed)
     size: SizeEmbed
 
-    @OneToMany(() => CatToyEntity, (catToy) => catToy.cat)
+    @OneToMany(() => CatToyEntity, (catToy) => catToy.cat, {
+        eager: true,
+    })
     toys: CatToyEntity[]
 
     @OneToOne(() => CatHomeEntity, (catHome) => catHome.cat, { nullable: true })

src/paginate.spec.ts

@@ -1981,4 +1981,24 @@ describe('paginate', () => {
 
         expect(result.data.length).toBe(4)
     })
+
+    it('should return eager relations when set the property `loadEagerRelations` as true', async () => {
+        const config: PaginateConfig<CatEntity> = {
+            sortableColumns: ['id'],
+            defaultSortBy: [['id', 'ASC']],
+            loadEagerRelations: true,
+            searchableColumns: ['name'],
+        }
+
+        const query: PaginateQuery = {
+            path: '',
+            search: 'Garfield',
+        }
+
+        const result = await paginate<CatEntity>(query, catRepo, config)
+
+        expect(result.data[0].toys).toBeDefined()
+
+        expect(result.data[0].toys).toHaveLength(1)
+    })
 })

src/paginate.ts

@@ -5,6 +5,7 @@ import {
     FindOptionsWhere,
     FindOptionsRelations,
     ObjectLiteral,
+    FindOptionsUtils,
 } from 'typeorm'
 import { PaginateQuery } from './decorator'
 import { ServiceUnavailableException, Logger } from '@nestjs/common'
@@ -62,6 +63,7 @@ export interface PaginateConfig<T> {
     filterableColumns?: {
         [key in Column<T>]?: (FilterOperator | FilterSuffix)[]
     }
+    loadEagerRelations?: boolean
     withDeleted?: boolean
     relativePath?: boolean
     origin?: string
@@ -146,6 +148,12 @@ export async function paginate<T extends ObjectLiteral>(
 
     const queryBuilder = repo instanceof Repository ? repo.createQueryBuilder('__root') : repo
 
+    if (repo instanceof Repository && !config.relations && config.loadEagerRelations === true) {
+        if (!config.relations) {
+            FindOptionsUtils.joinEagerRelations(queryBuilder, queryBuilder.alias, repo.metadata)
+        }
+    }
+
     if (isPaginated) {
         // Switch from take and skip to limit and offset
         // due to this problem https://github.com/typeorm/typeorm/issues/5670