new Value api, tests, docs

Author: renatorib

docs/components/Value.md

@@ -8,23 +8,23 @@ import { Value } from 'react-powerplug'
 
 ```jsx
 <Value initial="React">
-  {({ value, setValue }) => (
+  {({ value, set }) => (
     <Select
       label="Choose one"
       options={['React', 'Preact', 'Vue']}
       value={value}
-      onChange={setValue}
+      onChange={set}
     />
   )}
 </Value>
 ```
 
 ```jsx
 <Value initial="first">
-  {({ value, setValue }) => {
+  {({ value, set }) => {
     const bindRadio = radioValue => ({
       selected: value === radioValue,
-      onClick: () => setValue(radioValue),
+      onClick: () => set(radioValue),
     })
 
     return (
@@ -43,14 +43,17 @@ import { Value } from 'react-powerplug'
 **initial** _(required)_  
 Specifies the initial value state.
 
+**onChange** _(optional)_  
+Callback that fires when state changes.
+
 ## Value Children Props
 
-TL;DR: `{ value, setValue }`
+TL;DR: `{ value, set }`
 
 **value**  
 `T`  
 Your value state
 
-**setValue**  
-`(value: T) => void`  
-Set the value state
+**set**  
+`(value: T | (value: T) => T) => void`  
+Set or over the value state

src/components/Value.js

@@ -1,13 +1,14 @@
 import * as React from 'react'
 import State from './State'
 import renderProps from '../utils/renderProps'
+import set from '../utils/set'
 
 const Value = ({ initial, onChange, ...props }) => (
   <State initial={{ value: initial }} onChange={onChange}>
     {({ state, setState }) =>
       renderProps(props, {
         value: state.value,
-        setValue: value => setState({ value }),
+        set: value => setState(s => ({ value: set(value, s.value) })),
       })
     }
   </State>

tests/components/Value.test.js

@@ -11,11 +11,13 @@ test('<Value />', () => {
   expect(renderFn).toHaveBeenCalledTimes(1)
 
   expect(lastCalled().value).toEqual({ a: 1 })
-  lastCalled().setValue({ b: 2 })
 
+  lastCalled().set({ b: 2 })
   expect(lastCalled().value).toEqual({ b: 2 })
 
-  lastCalled().setValue(0)
+  lastCalled().set(value => ({ ...value, a: 1 }))
+  expect(lastCalled().value).toEqual({ a: 1, b: 2 })
 
+  lastCalled().set(0)
   expect(lastCalled().value).toEqual(0)
 })