From f9083401863c617d17f5703d66f89dc55dd752b1 Mon Sep 17 00:00:00 2001
From: Rasmus Eneman <rse@learningwell.se>
Date: Fri, 1 Dec 2017 14:30:39 +0100
Subject: [PATCH] [recompose]: Improve type inference of withHandlers

I went ahead and added the correspondeing tests on withStateHandlers as well to make sure it also works as expected
---
 types/recompose/index.d.ts          | 23 +++++++++++---
 types/recompose/recompose-tests.tsx | 48 +++++++++++++++++++++++++++--
 2 files changed, 63 insertions(+), 8 deletions(-)

diff --git a/types/recompose/index.d.ts b/types/recompose/index.d.ts
index edff2061b5..c057521570 100644
--- a/types/recompose/index.d.ts
+++ b/types/recompose/index.d.ts
@@ -3,6 +3,7 @@
 // Definitions by: Iskander Sierra <https://github.com/iskandersierra>
 //                 Samuel DeSota <https://github.com/mrapogee>
 //                 Curtis Layne <https://github.com/clayne11>
+//                 Rasmus Eneman <https://github.com/Pajn>
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
 // TypeScript Version: 2.6
 
@@ -78,13 +79,25 @@ declare module 'recompose' {
 
     // withHandlers: https://github.com/acdlite/recompose/blob/master/docs/API.md#withhandlers
     type EventHandler = Function;
-    type HandleCreators<TOutter, THandlers> = {
-        [handlerName in keyof THandlers]: mapper<TOutter, EventHandler>;
+    // This type is required to infer TOutter
+    type HandleCreatorsStructure<TOutter> = {
+        [handlerName: string]: mapper<TOutter, EventHandler>;
     };
-    type HandleCreatorsFactory<TOutter, THandlers> = (initialProps: TOutter) => HandleCreators<TOutter, THandlers>;
+    // This type is required to infer THandlers
+    type HandleCreatorsHandlers<TOutter, THandlers> = {
+        [P in keyof THandlers]: (props: TOutter) => THandlers[P];
+    };
+    type HandleCreators<TOutter, THandlers> =
+        & HandleCreatorsStructure<TOutter>
+        & HandleCreatorsHandlers<TOutter, THandlers>
+    type HandleCreatorsFactory<TOutter, THandlers> = (initialProps: TOutter) =>
+        HandleCreators<TOutter, THandlers>;
+
     export function withHandlers<TOutter, THandlers>(
-        handlerCreators: HandleCreators<TOutter, THandlers> | HandleCreatorsFactory<TOutter, THandlers>
-    ): InferableComponentEnhancerWithProps<TOutter & THandlers, TOutter>;
+        handlerCreators:
+            | HandleCreators<TOutter, THandlers>
+            | HandleCreatorsFactory<TOutter, THandlers>
+    ): InferableComponentEnhancerWithProps<THandlers & TOutter, TOutter>;
 
     // defaultProps: https://github.com/acdlite/recompose/blob/master/docs/API.md#defaultprops
     export function defaultProps<T = {}>(
diff --git a/types/recompose/recompose-tests.tsx b/types/recompose/recompose-tests.tsx
index 1504ab563a..c239cbacb1 100644
--- a/types/recompose/recompose-tests.tsx
+++ b/types/recompose/recompose-tests.tsx
@@ -120,10 +120,35 @@ function testWithHandlers() {
         />
     )
 
-    const handlerNameTypecheckProof = withHandlers<OutterProps, HandlerProps>({
+    const handlerNameTypecheckProof = withHandlers<OutterProps, HandlerProps>({ // $ExpectError
       onChange: () => () => {},
-      notAKeyOnHandlerProps: () => () => {},  // $ExpectError
+      notAKeyOnHandlerProps: () => () => {},
     });
+
+    // The inner props should be fully inferrable
+    const enhancer3 = withHandlers({
+      onChange: (props: OutterProps) => (e: any) => {},
+      onSubmit: (props: OutterProps) => (e: React.MouseEvent<any>) => {},
+    });
+    const Enhanced3 = enhancer3(({onChange, onSubmit, out}) =>
+        <div onClick={onSubmit}>{out}</div>);
+    const rendered3 = (
+        <Enhanced3
+            out={42}
+        />
+    )
+
+    const enhancer4 = withHandlers((props: OutterProps) => ({
+      onChange: (props) => (e: any) => {},
+      onSubmit: (props) => (e: React.MouseEvent<any>) => {},
+    }));
+    const Enhanced4 = enhancer4(({onChange, onSubmit, out}) =>
+        <div onClick={onSubmit}>{out}</div>);
+    const rendered4 = (
+        <Enhanced4
+            out={42}
+        />
+    )
 }
 
 function testDefaultProps() {
@@ -220,7 +245,24 @@ function testWithStateHandlers() {
         (props: OutterProps) => ({ counter: props.initialCounter }),
         { notAKeyOfUpdaters: (state, props) => n => ({ ...state, counter: state.counter + n ** props.power }), }, // $ExpectError
     );
-  }
+
+    // The inner props should be fully inferrable
+    const enhancer2 = withStateHandlers(
+        (props: OutterProps) => ({ counter: props.initialCounter }),
+        {
+            add: (state, props) => n => ({ ...state, counter: state.counter + n ** props.power }),
+        },
+    );
+    const Enhanced2 = enhancer((props) =>
+        <div>
+            <div>{`Counts from: ${props.initialCounter}`}</div>
+            <div>{`Counter: ${props.counter}`}</div>
+            <div onClick={() => props.add(2)}></div>
+        </div>);
+    const rendered2 = (
+        <Enhanced initialCounter={4} power={2} />
+    );
+}
 
 function testWithReducer() {
     interface State { count: number }