Remove pure option from connect

Author: markerikson

src/components/connect.tsx

@@ -236,7 +236,6 @@ export interface ConnectOptions<
 > {
   forwardRef?: boolean
   context?: typeof ReactReduxContext
-  pure?: boolean
   areStatesEqual?: (nextState: State, prevState: State) => boolean
 
   areOwnPropsEqual?: (
@@ -463,7 +462,9 @@ function connect<
   mapDispatchToProps?: MapDispatchToPropsParam<TDispatchProps, TOwnProps>,
   mergeProps?: MergeProps<TStateProps, TDispatchProps, TOwnProps, TMergedProps>,
   {
-    pure = true,
+    // The `pure` option has been removed, so TS doesn't like us destructuring this to check its existence.
+    // @ts-ignore
+    pure,
     areStatesEqual = strictEqual,
     areOwnPropsEqual = shallowEqual,
     areStatePropsEqual = shallowEqual,
@@ -476,6 +477,14 @@ function connect<
     context = ReactReduxContext,
   }: ConnectOptions<unknown, unknown, unknown, unknown> = {}
 ): unknown {
+  if (process.env.NODE_ENV !== 'production') {
+    if (pure !== undefined) {
+      throw new Error(
+        'The `pure` option has been removed. `connect` is now always a "pure/memoized" component'
+      )
+    }
+  }
+
   const Context = context
 
   type WrappedComponentProps = TOwnProps & ConnectProps
@@ -773,13 +782,14 @@ function connect<
     }
 
     // If we're in "pure" mode, ensure our wrapper component only re-renders when incoming props have changed.
-    const _Connect = pure ? React.memo(ConnectFunction) : ConnectFunction
+    const _Connect = React.memo(ConnectFunction)
 
     type ConnectedWrapperComponent = typeof _Connect & {
       WrappedComponent: typeof WrappedComponent
     }
 
-    const Connect = _Connect as ConnectedComponent<
+    // Add a hacky cast to get the right output type
+    const Connect = _Connect as unknown as ConnectedComponent<
       typeof WrappedComponent,
       WrappedComponentProps
     >

src/connect/mergeProps.ts

@@ -17,7 +17,6 @@ export function defaultMergeProps<TStateProps, TDispatchProps, TOwnProps>(
 
 interface InitMergeOptions {
   displayName: string
-  pure?: boolean
   areMergedPropsEqual: (a: any, b: any) => boolean
 }
 
@@ -34,7 +33,7 @@ export function wrapMergePropsFunc<
 ) => MergeProps<TStateProps, TDispatchProps, TOwnProps, TMergedProps> {
   return function initMergePropsProxy(
     dispatch,
-    { displayName, pure, areMergedPropsEqual }
+    { displayName, areMergedPropsEqual }
   ) {
     let hasRunOnce = false
     let mergedProps: TMergedProps
@@ -47,7 +46,7 @@ export function wrapMergePropsFunc<
       const nextMergedProps = mergeProps(stateProps, dispatchProps, ownProps)
 
       if (hasRunOnce) {
-        if (!pure || !areMergedPropsEqual(nextMergedProps, mergedProps))
+        if (!areMergedPropsEqual(nextMergedProps, mergedProps))
           mergedProps = nextMergedProps
       } else {
         hasRunOnce = true

src/connect/selectorFactory.ts

@@ -66,29 +66,6 @@ export type MergeProps<TStateProps, TDispatchProps, TOwnProps, TMergedProps> = (
   ownProps: TOwnProps
 ) => TMergedProps
 
-export function impureFinalPropsSelectorFactory<
-  TStateProps,
-  TOwnProps,
-  TDispatchProps,
-  TMergedProps,
-  State = DefaultRootState
->(
-  mapStateToProps: MapStateToPropsParam<TStateProps, TOwnProps, State>,
-  mapDispatchToProps: MapDispatchToPropsParam<TDispatchProps, TOwnProps>,
-  mergeProps: MergeProps<TStateProps, TDispatchProps, TOwnProps, TMergedProps>,
-  dispatch: Dispatch
-) {
-  return function impureFinalPropsSelector(state: State, ownProps: TOwnProps) {
-    return mergeProps(
-      // @ts-ignore
-      mapStateToProps(state, ownProps),
-      // @ts-ignore
-      mapDispatchToProps(dispatch, ownProps),
-      ownProps
-    )
-  }
-}
-
 interface PureSelectorFactoryComparisonOptions<
   TOwnProps,
   State = DefaultRootState
@@ -97,7 +74,6 @@ interface PureSelectorFactoryComparisonOptions<
   areOwnPropsEqual: EqualityFn<TOwnProps>
   areStatePropsEqual: EqualityFn<unknown>
   displayName: string
-  pure?: boolean
 }
 
 export function pureFinalPropsSelectorFactory<
@@ -222,10 +198,9 @@ export interface SelectorFactoryOptions<
 
 // TODO: Add more comments
 
-// If pure is true, the selector returned by selectorFactory will memoize its results,
+// The selector returned by selectorFactory will memoize its results,
 // allowing connect's shouldComponentUpdate to return false if final
-// props have not changed. If false, the selector will always return a new
-// object and shouldComponentUpdate will always return true.
+// props have not changed.
 
 export default function finalPropsSelectorFactory<
   TStateProps,
@@ -256,9 +231,7 @@ export default function finalPropsSelectorFactory<
     verifySubselectors(mapStateToProps, mapDispatchToProps, mergeProps)
   }
 
-  const selectorFactory = options.pure
-    ? pureFinalPropsSelectorFactory
-    : impureFinalPropsSelectorFactory
+  const selectorFactory = pureFinalPropsSelectorFactory
 
   return selectorFactory(
     // @ts-ignore