added pure option

- only re-render component if props or requests shallowly changed
- this.setAtomicState now creates new objects for all 4 keys
- added tests for `pure: true` and `pure: false`
- added `pure` option to api docs

Author: nfcampos

docs/api.md

@@ -122,6 +122,7 @@ const b = a.defaults({ withRef: false })
 
 * `[newOptions = {}]` *(Object)*: An object with any of the following keys:
     - `withRef` *(Boolean)*: If `true`, the connector will store a ref to the wrapped component instance and make it available via the `getWrappedInstance()` method. Defaults to `false`.
+    - `pure` *(Boolean)*: If `true`, the connector will treat the wrapped component and the mapPropsToRequestsToProps function as pure, recomputing requests and re-rendering only when props are shallowly different. If `false`, recompute and re-render every time props change. Defaults to `true`.
 
 ### `PromiseState`
 

src/components/connect.js

@@ -96,7 +96,8 @@ function connect(mapPropsToRequestsToProps, defaults, options) {
   checkTypes(defaults)
 
   options = Object.assign({
-    withRef: false
+    withRef: false,
+    pure: true
   }, options)
 
   // Helps track hot reloading.
@@ -183,13 +184,19 @@ function connect(mapPropsToRequestsToProps, defaults, options) {
 
       componentWillReceiveProps(nextProps, nextContext) {
         if (
+          !options.pure ||
           (dependsOnProps && !shallowEqual(omitChildren(this.props), omitChildren(nextProps))) ||
           (dependsOnContext && !shallowEqual(this.context, nextContext))
         ) {
           this.refetchDataFromProps(nextProps, nextContext)
         }
       }
 
+      shouldComponentUpdate(nextProps, nextState) {
+        return !options.pure ||
+          this.state.data != nextState.data || !shallowEqual(this.props, nextProps)
+      }
+
       componentWillUnmount() {
         this.clearAllRefreshTimeouts()
         this._unmounted = true
@@ -325,18 +332,22 @@ function connect(mapPropsToRequestsToProps, defaults, options) {
 
           return {
             startedAts: Object.assign(
+              {},
               prevState.startedAts, {
                 [prop]: startedAt
               }),
             mappings: Object.assign(
+              {},
               prevState.mappings, {
                 [prop]: mapping
               }),
             data: Object.assign(
+              {},
               prevState.data, {
                 [prop]: datum
               }),
             refreshTimeouts: Object.assign(
+              {},
               prevState.refreshTimeouts, {
                 [prop]: refreshTimeout
               })