feat: add additionalFields option to populate computed fields

README.md

@@ -120,6 +120,21 @@ crud('/admin/posts', actions, {
 })
 ```
 
+### Additional attributes
+
+Additional attributes can be populated in the read views. For example one can add a count of related records like this:
+
+```ts
+crud('/admin/categories', actions, {
+  additionalAttributes: async category => {
+    return {
+      postsCount: await Post.count({ categoryId: category.id })
+    }
+  },
+  additionalAttributesConcurrency: 10 // 10 queries Post.count will be perform at the same time
+})
+```
+
 ### Custom behavior & other ORMs
 
 ```ts

src/getList/index.ts

@@ -1,4 +1,5 @@
 import { RequestHandler, Request, Response } from 'express'
+import pLimit from 'p-limit';
 
 import { setGetListHeaders } from './headers'
 
@@ -12,15 +13,17 @@ export type Get<R> = (conf: {
   res: Response
 }) => Promise<{ rows: R[]; count: number }>
 
-export interface GetListOptions {
+export interface GetListOptions<R> {
   filters: FiltersOption
+  additionalAttributes: (record: R) => object | Promise<object>
+  additionalAttributesConcurrency: number
 }
 
 type FiltersOption = Record<string, (value: any) => any>
 
 export const getMany = <R>(
   doGetFilteredList: Get<R>,
-  options?: Partial<GetListOptions>
+  options?: Partial<GetListOptions<R>>
 ): RequestHandler => async (req, res, next) => {
   try {
     const { limit, offset, filter, order } = await parseQuery(
@@ -35,7 +38,11 @@ export const getMany = <R>(
       order,
     }, { req, res })
     setGetListHeaders(res, offset, count, rows.length)
-    res.json(rows)
+    res.json(
+      options?.additionalAttributes
+        ? await computeAdditionalAttributes(options.additionalAttributes, options.additionalAttributesConcurrency ?? 1)(rows)
+        : rows
+    )
 
   } catch (error) {
     next(error)
@@ -74,3 +81,13 @@ const getFilter = async (
 
   return result
 }
+
+
+const computeAdditionalAttributes =
+  <R>(additionalAttributes: GetListOptions<R>["additionalAttributes"], concurrency: number) => {
+    const limit = pLimit(concurrency)
+
+    return (records: R[]) => Promise.all(records.map(record =>
+      limit(async () => ({ ...record, ...await additionalAttributes(record) }))
+    ))
+  }

src/index.ts

@@ -20,7 +20,7 @@ export { Create, Destroy, Update, Get }
 export const crud = <I extends string | number, R>(
   path: string,
   actions: Partial<Actions<I, R>>,
-  options?: Partial<GetListOptions>
+  options?: Partial<GetListOptions<R>>
 ) => {
   const router = Router()
   router.use(bodyParser.json())

tests/index.spec.ts

@@ -55,6 +55,27 @@ describe('crud', () => {
           order: [['name', 'DESC']],
         }, expectReqRes)
       })
+
+
+      it('populates additional fields when provided', async () => {
+        const dataProvider = await setupApp(
+          crud<number, { id: number }>('/users', {
+            get: jest.fn().mockResolvedValue({ rows: [{ id: 1 }], count: 1 }),
+          }, {
+            additionalAttributes: async (record) => {
+              return { additionalProperty: await new Promise(resolve => resolve(`value ${record.id}`)) }
+            }
+          }),
+          ctx
+        )
+
+        const response = await dataProvider.getList('users', {
+          pagination: { page: 0, perPage: 25 },
+          sort: { field: 'id', order: 'DESC' },
+          filter: {},
+        })
+        expect(response.data[0]).toEqual({ id: 1, additionalProperty: 'value 1' })
+      })
     })
 
     describe('DELETE', () => {

yarn.lock

@@ -5304,6 +5304,13 @@ p-is-promise@^3.0.0:
   resolved "https://registry.yarnpkg.com/p-is-promise/-/p-is-promise-3.0.0.tgz#58e78c7dfe2e163cf2a04ff869e7c1dba64a5971"
   integrity sha512-Wo8VsW4IRQSKVXsJCn7TomUaVtyfjVDn3nUP7kE967BQk0CwFpdbZs0X0uk5sW9mkBa9eNM7hCMaG93WUAwxYQ==
 
+p-limit@3:
+  version "3.1.0"
+  resolved "https://registry.yarnpkg.com/p-limit/-/p-limit-3.1.0.tgz#e1daccbe78d0d1388ca18c64fea38e3e57e3706b"
+  integrity sha512-TYOanM3wGwNGsZN2cVTYPArw454xnXj5qmWF1bEoAc4+cU/ol7GVh7odevjp1FNHduHc3KZMcFduxU5Xc6uJRQ==
+  dependencies:
+    yocto-queue "^0.1.0"
+
 p-limit@^1.1.0:
   version "1.3.0"
   resolved "https://registry.yarnpkg.com/p-limit/-/p-limit-1.3.0.tgz#b86bd5f0c25690911c7590fcbfc2010d54b3ccb8"
@@ -6925,3 +6932,8 @@ yargs@^16.2.0:
     string-width "^4.2.0"
     y18n "^5.0.5"
     yargs-parser "^20.2.2"
+
+yocto-queue@^0.1.0:
+  version "0.1.0"
+  resolved "https://registry.yarnpkg.com/yocto-queue/-/yocto-queue-0.1.0.tgz#0294eb3dee05028d31ee1a5fa2c556a6aaf10a1b"
+  integrity sha512-rVksvsnNCdJ/ohGc6xgPwyN8eheCxsiLM8mxuE/t/mOVqJewPuO1miLpTHQiRgTKCLexL4MeAFVagts7HmNZ2Q==