feat: add map props feature

Author: pedronauck

README.md

@@ -14,6 +14,7 @@
 - [Usage](#--usage-demo)
   - [Working with new Context api](#working-with-new-context-api)
   - [Custom render and retrieving props from composed](#custom-render-and-retrieving-props-from-composed)
+  - [Mapping props from mappers](#mapping-props-from-mappers)
   - [Leading with multiple params](#leading-with-multiple-params)
   - [Typescript support](#typescript-support)
   - [Inline composition](#inline-composition)
@@ -133,6 +134,32 @@ const Composed = adopt({
 </Composed>
 ```
 
+### Mapping props from mappers
+
+Sometimes get properties from your mappers can be kind a boring depending how nest is the result from each mapper. To easily avoid deep nested objects or combine your results, you can map the final results into a single object using de `mapProps` function as second parameter.
+
+```js
+import { adopt } from 'react-adopt'
+import { Value } from 'react-powerplug'
+
+const mapper = {
+  greet: <Value initial="Hi" />,
+  name: <Value initial="John" />,
+}
+
+const mapProps = ({ greet, name }) => ({
+  message: `${greet.value} ${name.value}`,
+})
+
+const Composed = adopt(mapper, mapProps)
+
+const App = () => (
+  <Composed>
+    {({ message }) => /* ... */}
+  </Composed>
+)
+```
+
 ### Leading with multiple params
 
 Some render props components return multiple arguments in the children function instead of a single one (see a simple example in the new [Query](https://www.apollographql.com/docs/react/essentials/queries.html#basic) and [Mutation](https://www.apollographql.com/docs/react/essentials/mutations.html) component from `react-apollo`). In this case, you can do an arbitrary render with `render` prop [using your map value as a function](#custom-render-and-retrieving-props-from-composed):

src/index.test.tsx

@@ -149,3 +149,42 @@ test('inline composition using <Adopt> component', () => {
   expect(result.children().length).toBe(1)
   expect(result.html()).toBe('<div>foo</div>')
 })
+
+test('mapping props as second parameter of adopt()', () => {
+  const children = jest.fn(() => null)
+
+  const Composed = adopt(
+    {
+      foo: <Value initial="foo" />,
+      bar: <Value initial="bar" />,
+    },
+    ({ foo, bar }) => ({
+      foobar: foo.value + bar.value,
+    })
+  )
+
+  mount(<Composed>{children}</Composed>)
+
+  expect(children).toHaveBeenCalledWith({ foobar: 'foobar' })
+})
+
+test('mapping props as prop of <Adopt />', () => {
+  const children = jest.fn(() => null)
+
+  const mapper = {
+    foo: <Value initial="foo" />,
+    bar: <Value initial="bar" />,
+  }
+
+  const mapProps = ({ foo, bar }) => ({
+    foobar: foo.value + bar.value,
+  })
+
+  mount(
+    <Adopt mapper={mapper} mapProps={mapProps}>
+      {children}
+    </Adopt>
+  )
+
+  expect(children).toHaveBeenCalledWith({ foobar: 'foobar' })
+})

src/index.tsx

@@ -44,33 +44,45 @@ export declare type MapperValue<RP, P> =
 
 export declare type Mapper<RP, P> = Record<keyof RP, MapperValue<RP, P>>
 
-export function adopt<RP = any, P = any>(mapper: Mapper<RP, P>): RPC<RP, P> {
+export declare type MapProps<RP> = (props: any) => RP
+
+export function adopt<RP = any, P = any>(
+  mapper: Mapper<RP, P>,
+  mapProps?: MapProps<RP>
+): RPC<RP, P> {
   if (!values(mapper).some(isValidRenderProp)) {
     throw new Error(
       'The render props object mapper just accept valid elements as value'
     )
   }
 
+  const mapperKeys = keys(mapper)
   const Children: any = ({ children, ...rest }: any) =>
     isFn(children) && children(rest)
 
-  const reducer = (Component: RPC<RP>, key: string): RPC<RP> => ({
+  const reducer = (Component: RPC<RP>, key: string, idx: number): RPC<RP> => ({
     children,
     ...rest
   }) => (
     <Component {...rest}>
       {props => {
         const element = prop(key, mapper)
         const propsWithoutRest = omit<RP>(keys(rest), props)
+        const isLast = idx === mapperKeys.length - 1
+
+        const render: ChildrenFn<RP> = cProps => {
+          const renderProps = assign({}, propsWithoutRest, {
+            [key]: cProps,
+          })
 
-        const render: ChildrenFn<RP> = cProps =>
-          isFn(children)
+          return isFn(children)
             ? children(
-                assign({}, propsWithoutRest, {
-                  [key]: cProps,
-                })
+                mapProps && isFn(mapProps) && isLast
+                  ? mapProps(renderProps)
+                  : renderProps
               )
             : null
+        }
 
         return isFn(element)
           ? React.createElement(element, assign({}, rest, props, { render }))
@@ -79,20 +91,21 @@ export function adopt<RP = any, P = any>(mapper: Mapper<RP, P>): RPC<RP, P> {
     </Component>
   )
 
-  return keys(mapper).reduce(reducer, Children)
+  return mapperKeys.reduce(reducer, Children)
 }
 
 export type AdoptProps<RP, P> = P & {
   mapper: Mapper<RP, P>
   children: ChildrenFn<RP>
+  mapProps?: MapProps<RP>
 }
 
 export class Adopt extends React.Component<AdoptProps<any, any>> {
   Composed: React.ComponentType<any>
 
   constructor(props: any) {
     super(props)
-    this.Composed = adopt(props.mapper)
+    this.Composed = adopt(props.mapper, this.props.mapProps)
   }
 
   public render(): JSX.Element {