Flow strict StatusBar (facebook#22282)

Summary:
Related to facebook#22100

`Libraries/Components/StatusBar/StatusBar.js`
Enhance StatusBar with mergePropsStack and _defaultProps.

- [x] npm run prettier
- [x] npm run flow
- [x] npm run flow-check-ios
- [x] npm run flow-check-android
- [x] npm run lint
- [x] npm run test
- [x] ./scripts/run-android-local-unit-tests.sh

[GENERAL][ENHANCEMENT][StatusBar.js] - apply flow strict-local
Pull Request resolved: facebook#22282

Reviewed By: TheSavior

Differential Revision: D13103971

Pulled By: RSNara

fbshipit-source-id: 27f69c6df3a8a7792fcd595c0ff362943ccab8ca

Libraries/Components/StatusBar/StatusBar.js

@@ -5,7 +5,7 @@
  * LICENSE file in the root directory of this source tree.
  *
  * @format
- * @flow
+ * @flow strict-local
  */
 
 'use strict';
@@ -103,53 +103,88 @@ type Props = $ReadOnly<{|
   barStyle?: ?('default' | 'light-content' | 'dark-content'),
 |}>;
 
+type StackEntryProps = {|
+  /**
+   * The background color of the status bar.
+   *
+   * @platform android
+   */
+  backgroundColor: {|
+    value: ?string,
+    animated: ?boolean,
+  |},
+  /**
+   * Sets the color of the status bar text.
+   */
+  barStyle: {|
+    value: ?string,
+    animated: ?boolean,
+  |},
+  /**
+   * If the status bar is translucent.
+   * When translucent is set to true, the app will draw under the status bar.
+   * This is useful when using a semi transparent status bar color.
+   */
+  translucent: ?boolean,
+  /**
+   *
+   */
+  hidden: {|
+    value: ?boolean,
+    animated: boolean,
+    transition: ?('slide' | 'fade'),
+  |},
+  /**
+   * If the network activity indicator should be visible.
+   *
+   * @platform ios
+   */
+  networkActivityIndicatorVisible: ?boolean,
+|};
+
 /**
  * Merges the prop stack with the default values.
  */
 function mergePropsStack(
-  propsStack: Array<Object>,
-  defaultValues: Object,
-): Object {
+  propsStack: $ReadOnlyArray<StackEntryProps>,
+  defaultValues: StackEntryProps,
+): StackEntryProps {
+  const init: StackEntryProps = {
+    ...defaultValues,
+  };
+
   return propsStack.reduce((prev, cur) => {
     for (const prop in cur) {
       if (cur[prop] != null) {
         prev[prop] = cur[prop];
       }
     }
     return prev;
-  }, Object.assign({}, defaultValues));
+  }, init);
 }
 
 /**
  * Returns an object to insert in the props stack from the props
  * and the transition/animation info.
  */
-function createStackEntry(props: any): any {
+function createStackEntry(props: Props): StackEntryProps {
   return {
-    backgroundColor:
-      props.backgroundColor != null
-        ? {
-            value: props.backgroundColor,
-            animated: props.animated,
-          }
-        : null,
-    barStyle:
-      props.barStyle != null
-        ? {
-            value: props.barStyle,
-            animated: props.animated,
-          }
-        : null,
-    translucent: props.translucent,
-    hidden:
-      props.hidden != null
-        ? {
-            value: props.hidden,
-            animated: props.animated,
-            transition: props.showHideTransition,
-          }
-        : null,
-    networkActivityIndicatorVisible: props.networkActivityIndicatorVisible,
+    backgroundColor: {
+      value: props.backgroundColor,
+      animated: props.animated,
+    },
+    barStyle: {
+      value: props.barStyle,
+      animated: props.animated,
+    },
+    translucent: props.translucent || false,
+    hidden: {
+      value: props.hidden,
+      animated: props.animated || false,
+      transition: props.showHideTransition,
+    },
+    networkActivityIndicatorVisible:
+      props.networkActivityIndicatorVisible || false,
   };
 }
 
@@ -193,9 +228,9 @@ function createStackEntry(props: any): any {
  * `currentHeight` (Android only) The height of the status bar.
  */
 class StatusBar extends React.Component<Props> {
-  static _propsStack = [];
+  static _propsStack: Array<StackEntryProps> = [];
 
-  static _defaultProps = createStackEntry({
+  static _defaultProps: StackEntryProps = createStackEntry({
     animated: false,
     showHideTransition: 'fade',
     backgroundColor: 'black',
@@ -230,10 +265,9 @@ class StatusBar extends React.Component<Props> {
    *    changing the status bar hidden property.
    */
   static setHidden(hidden: boolean, animation?: StatusBarAnimation) {
-    animation = animation || 'none';
     StatusBar._defaultProps.hidden.value = hidden;
     if (Platform.OS === 'ios') {
-      StatusBarManager.setHidden(hidden, animation);
+      StatusBarManager.setHidden(hidden, animation || 'none');
     } else if (Platform.OS === 'android') {
       StatusBarManager.setHidden(hidden);
     }
@@ -245,10 +279,9 @@ class StatusBar extends React.Component<Props> {
    * @param animated Animate the style change.
    */
   static setBarStyle(style: StatusBarStyle, animated?: boolean) {
-    animated = animated || false;
     StatusBar._defaultProps.barStyle.value = style;
     if (Platform.OS === 'ios') {
-      StatusBarManager.setStyle(style, animated);
+      StatusBarManager.setStyle(style, animated || false);
     } else if (Platform.OS === 'android') {
       StatusBarManager.setStyle(style);
     }
@@ -279,9 +312,8 @@ class StatusBar extends React.Component<Props> {
       console.warn('`setBackgroundColor` is only available on Android');
       return;
     }
-    animated = animated || false;
     StatusBar._defaultProps.backgroundColor.value = color;
-    StatusBarManager.setColor(processColor(color), animated);
+    StatusBarManager.setColor(processColor(color), animated || false);
   }
 
   /**