Improve flow typing

Summary:
- Properly inherit flow types from base components, including `defaultProps`
- template-ify the `Item` type as it flows from the `data` prop into `ItemComponent`

Note that for `SectionList` is is harder to do the `Item` typing because each section in the
`sections` array can have a different `Item` type, plus all the optional overrides...not sure how to
tackle that.

Reviewed By: yungsters

Differential Revision: D4557523

fbshipit-source-id: a0c5279fcdaabe6aab5fe11743a99c3715a44032

Author: sahrens

.flowconfig

@@ -44,6 +44,7 @@ suppress_type=$FixMe
 suppress_comment=\\(.\\|\n\\)*\\$FlowFixMe\\($\\|[^(]\\|(\\(>=0\\.\\(3[0-9]\\|[1-2][0-9]\\|[0-9]\\).[0-9]\\)? *\\(site=[a-z,_]*react_native_oss[a-z,_]*\\)?)\\)
 suppress_comment=\\(.\\|\n\\)*\\$FlowIssue\\((\\(>=0\\.\\(3[0-9]\\|1[0-9]\\|[1-2][0-9]\\).[0-9]\\)? *\\(site=[a-z,_]*react_native_oss[a-z,_]*\\)?)\\)?:? #[0-9]+
 suppress_comment=\\(.\\|\n\\)*\\$FlowFixedInNextDeploy
+suppress_comment=\\(.\\|\n\\)*\\$FlowExpectedError
 
 unsafe.enable_getters_and_setters=true
 

Examples/UIExplorer/js/FlatListExample.js

@@ -108,7 +108,7 @@ class FlatListExample extends React.PureComponent {
           key={(this.state.horizontal ? 'h' : 'v') + (this.state.fixedHeight ? 'f' : 'd')}
           legacyImplementation={false}
           numColumns={1}
-          onRefresh={() => alert('onRefresh: nothing to refresh :P')}
+          onRefresh={this._onRefresh}
           onViewableItemsChanged={this._onViewableItemsChanged}
           ref={this._captureRef}
           refreshing={false}
@@ -121,6 +121,7 @@ class FlatListExample extends React.PureComponent {
   _getItemLayout = (data: any, index: number) => {
     return getItemLayout(data, index, this.state.horizontal);
   };
+  _onRefresh = () => alert('onRefresh: nothing to refresh :P');
   _renderItemComponent = ({item}) => {
     return (
       <ItemComponent
@@ -154,7 +155,7 @@ class FlatListExample extends React.PureComponent {
   _pressItem = (key: number) => {
     pressItem(this, key);
   };
-  _listRef: FlatList;
+  _listRef: FlatList<*>;
 }
 
 

Libraries/Experimental/FlatList.js

@@ -41,22 +41,23 @@ const invariant = require('invariant');
 
 import type {StyleObj} from 'StyleSheetTypes';
 import type {Viewable} from 'ViewabilityHelper';
+import type {Props as VirtualizedListProps} from 'VirtualizedList';
 
 type Item = any;
 
-type RequiredProps = {
+type RequiredProps<ItemT> = {
   /**
    * Note this can be a normal class component, or a functional component, such as a render method
    * on your main component.
    */
-  ItemComponent: ReactClass<{item: Item, index: number}>,
+  ItemComponent: ReactClass<{item: ItemT, index: number}>,
   /**
    * For simplicity, data is just a plain array. If you want to use something else, like an
    * immutable list, use the underlying `VirtualizedList` directly.
    */
-  data: ?Array<Item>,
+  data: ?Array<ItemT>,
 };
-type OptionalProps = {
+type OptionalProps<ItemT> = {
   /**
    * Rendered at the bottom of all the items.
    */
@@ -79,7 +80,7 @@ type OptionalProps = {
    * Remember to include separator length (height or width) in your offset calculation if you
    * specify `SeparatorComponent`.
    */
-  getItemLayout?: (data: ?Array<Item>, index: number) =>
+  getItemLayout?: (data: ?Array<ItemT>, index: number) =>
     {length: number, offset: number, index: number},
   /**
    * If true, renders items next to each other horizontally instead of stacked vertically.
@@ -90,7 +91,7 @@ type OptionalProps = {
    * and as the react key to track item re-ordering. The default extractor checks item.key, then
    * falls back to using the index, like react does.
    */
-  keyExtractor: (item: Item, index: number) => string,
+  keyExtractor: (item: ItemT, index: number) => string,
   /**
    * Multiple columns can only be rendered with horizontal={false} and will zig-zag like a flexWrap
    * layout. Items should all be the same height - masonry layouts are not supported.
@@ -111,6 +112,7 @@ type OptionalProps = {
    * `viewablePercentThreshold` prop.
    */
   onViewableItemsChanged?: ?({viewableItems: Array<Viewable>, changed: Array<Viewable>}) => void,
+  legacyImplementation?: ?boolean,
   /**
    * Set this true while waiting for new data from a refresh.
    */
@@ -123,11 +125,19 @@ type OptionalProps = {
    * Optional optimization to minimize re-rendering items.
    */
   shouldItemUpdate: (
-    prevProps: {item: Item, index: number},
-    nextProps: {item: Item, index: number}
+    prevProps: {item: ItemT, index: number},
+    nextProps: {item: ItemT, index: number}
   ) => boolean,
 };
-type Props = RequiredProps & OptionalProps; // plus props from the underlying implementation
+type Props<ItemT> = RequiredProps<ItemT> & OptionalProps<ItemT> & VirtualizedListProps;
+
+const defaultProps = {
+  ...VirtualizedList.defaultProps,
+  getItem: undefined,
+  getItemCount: undefined,
+  numColumns: 1,
+};
+type DefaultProps = typeof defaultProps;
 
 /**
  * A performant interface for rendering simple, flat lists, supporting the most handy features:
@@ -148,13 +158,9 @@ type Props = RequiredProps & OptionalProps; // plus props from the underlying im
  *     ItemComponent={({item}) => <Text>{item.key}</Text>}
  *   />
  */
-class FlatList extends React.PureComponent {
-  static defaultProps = {
-    keyExtractor: VirtualizedList.defaultProps.keyExtractor,
-    numColumns: 1,
-    shouldItemUpdate: VirtualizedList.defaultProps.shouldItemUpdate,
-  };
-  props: Props;
+class FlatList<ItemT> extends React.PureComponent<DefaultProps, Props<ItemT>, void> {
+  static defaultProps: DefaultProps = defaultProps;
+  props: Props<ItemT>;
   /**
    * Scrolls to the end of the content. May be janky without getItemLayout prop.
    */
@@ -191,7 +197,7 @@ class FlatList extends React.PureComponent {
     this._checkProps(this.props);
   }
 
-  componentWillReceiveProps(nextProps: Props) {
+  componentWillReceiveProps(nextProps: Props<ItemT>) {
     this._checkProps(nextProps);
   }
 
@@ -200,7 +206,7 @@ class FlatList extends React.PureComponent {
 
   _captureRef = (ref) => { this._listRef = ref; };
 
-  _checkProps(props: Props) {
+  _checkProps(props: Props<ItemT>) {
     const {
       getItem,
       getItemCount,
@@ -229,7 +235,7 @@ class FlatList extends React.PureComponent {
     }
   }
 
-  _getItem = (data: Array<Item>, index: number): Item | Array<Item> => {
+  _getItem = (data: Array<ItemT>, index: number): ItemT | Array<ItemT> => {
     const {numColumns} = this.props;
     if (numColumns > 1) {
       const ret = [];
@@ -243,13 +249,19 @@ class FlatList extends React.PureComponent {
     }
   };
 
-  _getItemCount = (data: Array<Item>): number => {
+  _getItemCount = (data: Array<ItemT>): number => {
     return Math.floor(data.length / this.props.numColumns);
   };
 
-  _keyExtractor = (items: Item | Array<Item>, index: number): string => {
+  _keyExtractor = (items: ItemT | Array<ItemT>, index: number): string => {
     const {keyExtractor, numColumns} = this.props;
     if (numColumns > 1) {
+      invariant(
+        Array.isArray(items),
+        'FlatList: Encountered internal consistency error, expected each item to consist of an ' +
+        'array with 1-%s columns; instead, received a single item.',
+        numColumns,
+      );
       return items.map((it, kk) => keyExtractor(it, index * numColumns + kk)).join(':');
     } else {
       return keyExtractor(items, index);

Libraries/Experimental/MetroListView.js

@@ -49,7 +49,7 @@ type NormalProps = {
 
   // Provide either `items` or `sections`
   items?: ?Array<Item>, // By default, an Item is assumed to be {key: string}
-  sections?: ?Array<{key: string, items: Array<Item>}>,
+  sections?: ?Array<{key: string, data: Array<Item>}>,
 
   /**
    * If provided, a standard RefreshControl will be added for "Pull to Refresh" functionality. Make
@@ -146,7 +146,7 @@ class MetroListView extends React.Component {
       const sections = {};
       props.sections.forEach((sectionIn, ii) => {
         const sectionID = 's' + ii;
-        sections[sectionID] = sectionIn.itemData;
+        sections[sectionID] = sectionIn.data;
         sectionHeaderData[sectionID] = sectionIn;
       });
       return {

Libraries/Experimental/SectionList.js

@@ -37,43 +37,43 @@ const React = require('React');
 const VirtualizedSectionList = require('VirtualizedSectionList');
 
 import type {Viewable} from 'ViewabilityHelper';
+import type {Props as VirtualizedSectionListProps} from 'VirtualizedSectionList';
 
 type Item = any;
-type SectionItem = any;
 
-type SectionBase = {
+type SectionBase<SectionItemT> = {
   // Must be provided directly on each section.
-  data: Array<SectionItem>,
+  data: Array<SectionItemT>,
   key: string,
 
   // Optional props will override list-wide props just for this section.
-  ItemComponent?: ?ReactClass<{item: SectionItem, index: number}>,
+  ItemComponent?: ?ReactClass<{item: SectionItemT, index: number}>,
   SeparatorComponent?: ?ReactClass<*>,
-  keyExtractor?: (item: SectionItem) => string,
+  keyExtractor?: (item: SectionItemT) => string,
 
   // TODO: support more optional/override props
   // FooterComponent?: ?ReactClass<*>,
   // HeaderComponent?: ?ReactClass<*>,
   // onViewableItemsChanged?: ({viewableItems: Array<Viewable>, changed: Array<Viewable>}) => void,
 
   // TODO: support recursive sections
-  // SectionHeaderComponent?: ?ReactClass<{section: SectionBase}>,
+  // SectionHeaderComponent?: ?ReactClass<{section: SectionBase<*>}>,
   // sections?: ?Array<Section>;
 };
 
-type RequiredProps<SectionT: SectionBase> = {
+type RequiredProps<SectionT: SectionBase<*>> = {
   sections: Array<SectionT>,
 };
 
-type OptionalProps<SectionT: SectionBase> = {
+type OptionalProps<SectionT: SectionBase<*>> = {
   /**
    * Rendered after the last item in the last section.
    */
   FooterComponent?: ?ReactClass<*>,
   /**
    * Default renderer for every item in every section.
    */
-  ItemComponent?: ?ReactClass<{item: Item, index: number}>,
+  ItemComponent: ReactClass<{item: Item, index: number}>,
   /**
    * Rendered at the top of each section. In the future, a sticky option will be added.
    */
@@ -93,8 +93,8 @@ type OptionalProps<SectionT: SectionBase> = {
    * stored outside of the recursive `ItemComponent` instance tree.
    */
   enableVirtualization?: ?boolean,
-  keyExtractor?: (item: Item) => string,
-  onEndReached?: ({distanceFromEnd: number}) => void,
+  keyExtractor: (item: Item, index: number) => string,
+  onEndReached?: ?({distanceFromEnd: number}) => void,
   /**
    * If provided, a standard RefreshControl will be added for "Pull to Refresh" functionality. Make
    * sure to also set the `refreshing` prop correctly.
@@ -104,21 +104,25 @@ type OptionalProps<SectionT: SectionBase> = {
    * Called when the viewability of rows changes, as defined by the
    * `viewablePercentThreshold` prop.
    */
-  onViewableItemsChanged?: ({viewableItems: Array<Viewable>, changed: Array<Viewable>}) => void,
+  onViewableItemsChanged?: ?({viewableItems: Array<Viewable>, changed: Array<Viewable>}) => void,
   /**
    * Set this true while waiting for new data from a refresh.
    */
-  refreshing?: boolean,
+  refreshing?: ?boolean,
   /**
    * This is an optional optimization to minimize re-rendering items.
    */
-  shouldItemUpdate?: (
+  shouldItemUpdate: (
     prevProps: {item: Item, index: number},
     nextProps: {item: Item, index: number}
   ) => boolean,
 };
 
-type Props<SectionT> = RequiredProps<SectionT> & OptionalProps<SectionT>;
+type Props<SectionT> = RequiredProps<SectionT>
+  & OptionalProps<SectionT>
+  & VirtualizedSectionListProps<SectionT>;
+
+type DefaultProps = typeof VirtualizedSectionList.defaultProps;
 
 /**
  * A performant interface for rendering sectioned lists, supporting the most handy features:
@@ -132,8 +136,11 @@ type Props<SectionT> = RequiredProps<SectionT> & OptionalProps<SectionT>;
  *
  * If you don't need section support and want a simpler interface, use FlatList.
  */
-class SectionList<SectionT: SectionBase> extends React.Component<void, Props<SectionT>, void> {
+class SectionList<SectionT: SectionBase<*>>
+  extends React.PureComponent<DefaultProps, Props<SectionT>, *>
+{
   props: Props<SectionT>;
+  static defaultProps: DefaultProps = VirtualizedSectionList.defaultProps;
 
   render() {
     if (this.props.legacyImplementation) {

Libraries/Experimental/VirtualizedList.js

@@ -68,7 +68,7 @@ type RequiredProps = {
    * The default accessor functions assume this is an Array<{key: string}> but you can override
    * getItem, getItemCount, and keyExtractor to handle any type of index-based data.
    */
-  data: any,
+  data?: any,
 };
 type OptionalProps = {
   FooterComponent?: ?ReactClass<*>,
@@ -89,12 +89,12 @@ type OptionalProps = {
   getItemCount: (items: any) => number,
   getItemLayout?: (items: any, index: number) =>
     {length: number, offset: number, index: number}, // e.g. height, y
-  horizontal: boolean,
+  horizontal?: ?boolean,
   initialNumToRender: number,
   keyExtractor: (item: Item, index: number) => string,
   maxToRenderPerBatch: number,
-  onEndReached: ({distanceFromEnd: number}) => void,
-  onEndReachedThreshold: number, // units of visible length
+  onEndReached?: ?({distanceFromEnd: number}) => void,
+  onEndReachedThreshold?: ?number, // units of visible length
   onLayout?: ?Function,
   /**
    * If provided, a standard RefreshControl will be added for "Pull to Refresh" functionality. Make
@@ -105,11 +105,11 @@ type OptionalProps = {
    * Called when the viewability of rows changes, as defined by the
    * `viewablePercentThreshold` prop.
    */
-  onViewableItemsChanged?: ({viewableItems: Array<Viewable>, changed: Array<Viewable>}) => void,
+  onViewableItemsChanged?: ?({viewableItems: Array<Viewable>, changed: Array<Viewable>}) => void,
   /**
    * Set this true while waiting for new data from a refresh.
    */
-  refreshing?: boolean,
+  refreshing?: ?boolean,
   removeClippedSubviews?: boolean,
   renderScrollComponent: (props: Object) => React.Element<*>,
   shouldItemUpdate: (
@@ -126,11 +126,11 @@ type OptionalProps = {
   viewablePercentThreshold: number,
   windowSize: number, // units of visible length
 };
-type Props = RequiredProps & OptionalProps;
+export type Props = RequiredProps & OptionalProps;
 
 let _usedIndexForKey = false;
 
-class VirtualizedList extends React.PureComponent {
+class VirtualizedList extends React.PureComponent<OptionalProps, Props, *> {
   props: Props;
 
   // scrollToEnd may be janky without getItemLayout prop
@@ -182,7 +182,7 @@ class VirtualizedList extends React.PureComponent {
     );
   }
 
-  static defaultProps: OptionalProps = {
+  static defaultProps = {
     disableVirtualization: false,
     getItem: (data: any, index: number) => data[index],
     getItemCount: (data: any) => data ? data.length : 0,
@@ -390,7 +390,12 @@ class VirtualizedList extends React.PureComponent {
 
   _onCellLayout = (e, cellKey, index) => {
     const layout = e.nativeEvent.layout;
-    const next = {offset: this._selectOffset(layout), length: this._selectLength(layout), index, inLayout: true};
+    const next = {
+      offset: this._selectOffset(layout),
+      length: this._selectLength(layout),
+      index,
+      inLayout: true,
+    };
     const curr = this._frames[cellKey];
     if (!curr ||
       next.offset !== curr.offset ||