Improve Flow Type for ScrollResponder

Summary: FlatList and VirtualizedList were typing this value as any instead of using the actual type from ScrollView. I started with that change and then fixed the type to solve the other callsites in the codebase.

Reviewed By: zackargyle

Differential Revision: D17089934

fbshipit-source-id: bfc22cec9993904d779cad37b1de7cb3c0484d2c

Libraries/Components/ScrollView/ScrollView.js

@@ -64,7 +64,21 @@ if (Platform.OS === 'android') {
 }
 
 export type ScrollResponderType = {
-  ...ScrollView,
+  // We'd like to do ...ScrollView here, however Flow doesn't seem
+  // to see the imperative methods of ScrollView that way. Workaround the
+  // issue by specifying them manually.
+  getScrollableNode: $PropertyType<ScrollView, 'getScrollableNode'>,
+  getInnerViewNode: $PropertyType<ScrollView, 'getInnerViewNode'>,
+  getNativeScrollRef: $PropertyType<ScrollView, 'getNativeScrollRef'>,
+
+  setNativeProps: $PropertyType<ScrollView, 'setNativeProps'>,
+  scrollTo: $PropertyType<ScrollView, 'scrollTo'>,
+  scrollWithoutAnimationTo: $PropertyType<
+    ScrollView,
+    'scrollWithoutAnimationTo',
+  >,
+  flashScrollIndicators: $PropertyType<ScrollView, 'flashScrollIndicators'>,
+
   ...typeof ScrollResponder.Mixin,
 };
 

Libraries/Lists/FlatList.js

@@ -18,6 +18,7 @@ const StyleSheet = require('../StyleSheet/StyleSheet');
 
 const invariant = require('invariant');
 
+import type {ScrollResponderType} from '../Components/ScrollView/ScrollView';
 import type {ViewStyleProp} from '../StyleSheet/StyleSheet';
 import type {
   ViewabilityConfig,
@@ -445,7 +446,7 @@ class FlatList<ItemT> extends React.PureComponent<Props<ItemT>, void> {
   /**
    * Provides a handle to the underlying scroll responder.
    */
-  getScrollResponder(): any {
+  getScrollResponder(): ?ScrollResponderType {
     if (this._listRef) {
       return this._listRef.getScrollResponder();
     }

Libraries/Lists/SectionList.js

@@ -14,6 +14,7 @@ const React = require('react');
 const ScrollView = require('../Components/ScrollView/ScrollView');
 const VirtualizedSectionList = require('./VirtualizedSectionList');
 
+import type {ScrollResponderType} from '../Components/ScrollView/ScrollView';
 import type {ViewToken} from './ViewabilityHelper';
 import type {
   SectionBase as _SectionBase,
@@ -275,7 +276,7 @@ class SectionList<SectionT: SectionBase<any>> extends React.PureComponent<
   /**
    * Provides a handle to the underlying scroll responder.
    */
-  getScrollResponder(): ?ScrollView {
+  getScrollResponder(): ?ScrollResponderType {
     const listRef = this._wrapperListRef && this._wrapperListRef.getListRef();
     if (listRef) {
       return listRef.getScrollResponder();

Libraries/Lists/VirtualizedList.js

@@ -27,6 +27,7 @@ const warning = require('fbjs/lib/warning');
 
 const {computeWindowedRenderLimits} = require('./VirtualizeUtils');
 
+import type {ScrollResponderType} from '../Components/ScrollView/ScrollView';
 import type {ViewStyleProp} from '../StyleSheet/StyleSheet';
 import type {
   ViewabilityConfig,
@@ -431,7 +432,7 @@ class VirtualizedList extends React.PureComponent<Props, State> {
    * Note that `this._scrollRef` might not be a `ScrollView`, so we
    * need to check that it responds to `getScrollResponder` before calling it.
    */
-  getScrollResponder(): any {
+  getScrollResponder(): ?ScrollResponderType {
     if (this._scrollRef && this._scrollRef.getScrollResponder) {
       return this._scrollRef.getScrollResponder();
     }