[flow] Support custom navigators using Transitioner (react-navigation#5801)

Author: Ashoat

flow/react-navigation.js

@@ -238,6 +238,7 @@ declare module 'react-navigation' {
      */
     index: number,
     routes: Array<NavigationRoute>,
+    isTransitioning?: boolean,
   };
 
   declare export type NavigationRoute =
@@ -407,7 +408,9 @@ declare module 'react-navigation' {
     NavigationSceneRendererProps & {
       mode: HeaderMode,
       router: NavigationRouter<NavigationState, NavigationStackScreenOptions>,
-      getScreenDetails: NavigationScene => NavigationScreenDetails<NavigationStackScreenOptions>,
+      getScreenDetails: NavigationScene => NavigationScreenDetails<
+        NavigationStackScreenOptions
+      >,
       leftInterpolator: (props: NavigationSceneRendererProps) => {},
       titleInterpolator: (props: NavigationSceneRendererProps) => {},
       rightInterpolator: (props: NavigationSceneRendererProps) => {},
@@ -466,10 +469,10 @@ declare module 'react-navigation' {
     disableKeyboardHandling?: boolean,
   |};
 
-  declare export type StackNavigatorConfig = {|
+  declare export type StackNavigatorConfig = $Shape<{|
     ...NavigationStackViewConfig,
     ...NavigationStackRouterConfig,
-  |};
+  |}>;
 
   /**
    * Switch Navigator
@@ -658,7 +661,9 @@ declare module 'react-navigation' {
     onWillBlur?: NavigationEventCallback,
     onDidBlur?: NavigationEventCallback,
   };
-  declare export var NavigationEvents: React$ComponentType<_NavigationEventsProps>;
+  declare export var NavigationEvents: React$ComponentType<
+    _NavigationEventsProps
+  >;
 
   /**
    * Navigation container
@@ -709,6 +714,7 @@ declare module 'react-navigation' {
     isStale: boolean,
     key: string,
     route: NavigationRoute,
+    descriptor: ?NavigationDescriptor,
   };
 
   declare export type NavigationTransitionProps = $Shape<{
@@ -920,9 +926,9 @@ declare module 'react-navigation' {
     router: NavigationRouter<S, O>,
   };
 
-  declare type NavigationDescriptor = {
+  declare export type NavigationDescriptor = {
     key: string,
-    state: NavigationLeafRoute | NavigationStateRoute,
+    state: NavigationRoute,
     navigation: NavigationScreenProp<*>,
     getComponent: () => React$ComponentType<{}>,
   };
@@ -1037,7 +1043,9 @@ declare module 'react-navigation' {
      */
     transitionConfig?: () => TransitionConfig,
   } & NavigationNavigatorProps<NavigationStackScreenOptions, NavigationState>;
-  declare export var CardStackTransitioner: React$ComponentType<_CardStackTransitionerProps>;
+  declare export var CardStackTransitioner: React$ComponentType<
+    _CardStackTransitionerProps
+  >;
 
   declare type _CardStackProps = {
     screenProps?: {},
@@ -1108,7 +1116,9 @@ declare module 'react-navigation' {
     truncatedTitle?: ?string,
     width?: ?number,
   };
-  declare export var HeaderBackButton: React$ComponentType<_HeaderBackButtonProps>;
+  declare export var HeaderBackButton: React$ComponentType<
+    _HeaderBackButtonProps
+  >;
 
   declare type _DrawerViewProps = {
     drawerLockMode?: 'unlocked' | 'locked-closed' | 'locked-open',