feat: add a setOptions function and useOptions hook

In React Navigation, the screen options can be specified statically. If you need to configure any options based on props and state of the component, or want to update state and props based on some action such as tab press, you need to do it in a hacky way by changing params. it's way more complicated than it needs to be. It also breaks when used with HOCs which don't hoist static props, a common source of confusion.

This PR adds a `setOptions` API to be able to update options directly without going through params, and an `useOptions` hook to make it easier to set them.

README.md

@@ -109,6 +109,30 @@ A render callback which doesn't have such limitation and is easier to use for th
 
 The rendered component will receives a `navigation` prop with various helpers and a `route` prop which represents the route being rendered.
 
+## Setting screen options
+
+In React Navigation, screen options can be specified in a static property on the component (`navigationOptions`). This poses few issues:
+
+- It's not possible to configure options based on props, state or context
+- To update the props based on an action in the component (such as button press), we need to do it in a hacky way by changing params
+- It breaks when used with HOCs which don't hoist static props, which is a common source of confusion
+
+Instead of a static property, we expose a hook to configure screen options:
+
+```js
+function Selection() {
+  const [selectedIds, setSelectedIds] = React.useState([]);
+
+  useOptions({
+    title: `${selectedIds.length} items selected`,
+  });
+
+  return <SelectionList onSelect={id => setSelectedIds(ids => [...ids, id])} />;
+}
+```
+
+This allows options to be changed based on props, state or context, and doesn't have the disadvantages of static configuration.
+
 ## Type-checking
 
 The library exports few helper types. Each navigator also need to export a custom type for the `navigation` prop which should contain the actions they provide, .e.g. `push` for stack, `jumpTo` for tab etc.
@@ -182,4 +206,16 @@ And then we can use it:
 </Stack.Navigator>
 ```
 
+To provide type-checking in the `useOptions` hook, we can provide it a type parameter:
+
+```ts
+function Profile({ userId }: Props) {
+  useOptions<StackNavigationOptions>({
+    title: `${userId}'s profile`,
+  });
+
+  // Content
+}
+```
+
 Unfortunately it's not possible to verify that the type of children elements are correct since [TypeScript doesn't support type-checking JSX elements](https://github.com/microsoft/TypeScript/issues/21699).

example/index.tsx

@@ -6,8 +6,12 @@ import {
   PartialState,
   NavigationProp,
   RouteProp,
+  useOptions,
 } from '../src';
-import StackNavigator, { StackNavigationProp } from './StackNavigator';
+import StackNavigator, {
+  StackNavigationProp,
+  StackNavigationOptions,
+} from './StackNavigator';
 import TabNavigator, { TabNavigationProp } from './TabNavigator';
 
 type StackParamList = {
@@ -65,20 +69,34 @@ const Second = ({
     StackNavigationProp<StackParamList>,
     NavigationProp<TabParamList>
   >;
-}) => (
-  <div>
-    <h1>Second</h1>
-    <button
-      type="button"
-      onClick={() => navigation.push('first', { author: 'Joel' })}
-    >
-      Push first
-    </button>
-    <button type="button" onClick={() => navigation.pop()}>
-      Pop
-    </button>
-  </div>
-);
+}) => {
+  const [count, setCount] = React.useState(0);
+
+  React.useEffect(() => {
+    const timer = setInterval(() => setCount(c => c + 1), 1000);
+
+    return () => clearInterval(timer);
+  }, []);
+
+  useOptions<StackNavigationOptions>({
+    title: `Count ${count}`,
+  });
+
+  return (
+    <div>
+      <h1>Second</h1>
+      <button
+        type="button"
+        onClick={() => navigation.push('first', { author: 'Joel' })}
+      >
+        Push first
+      </button>
+      <button type="button" onClick={() => navigation.pop()}>
+        Pop
+      </button>
+    </div>
+  );
+};
 
 const Fourth = ({
   navigation,

src/SceneView.tsx

@@ -17,6 +17,9 @@ type Props = {
   route: Route & { state?: NavigationState };
   getState: () => NavigationState;
   setState: (state: NavigationState) => void;
+  setOptions: (
+    cb: (options: { [key: string]: object }) => { [key: string]: object }
+  ) => void;
 };
 
 export default function SceneView({
@@ -25,6 +28,7 @@ export default function SceneView({
   navigation: helpers,
   getState,
   setState,
+  setOptions,
 }: Props) {
   const { performTransaction } = React.useContext(NavigationStateContext);
 
@@ -34,8 +38,16 @@ export default function SceneView({
       setParams: (params: object, target?: TargetRoute<string>) => {
         helpers.setParams(params, target ? target : { key: route.key });
       },
+      setOptions: (options: object) =>
+        setOptions(o => ({
+          ...o,
+          [route.key]: {
+            ...o[route.key],
+            ...options,
+          },
+        })),
     }),
-    [helpers, route.key]
+    [helpers, route.key, setOptions]
   );
 
   const getCurrentState = React.useCallback(() => {

src/index.tsx

@@ -4,5 +4,6 @@ export { default as createNavigator } from './createNavigator';
 
 export { default as useNavigationBuilder } from './useNavigationBuilder';
 export { default as useNavigation } from './useNavigation';
+export { default as useOptions } from './useOptions';
 
 export * from './types';

src/types.tsx

@@ -208,6 +208,14 @@ export type NavigationProp<ParamList extends ParamListBase = ParamListBase> = {
     params: ParamList[RouteName],
     target: TargetRoute<RouteName>
   ): void;
+
+  /**
+   * Update the options for the route.
+   * The options object will be shallow merged with default options object.
+   *
+   * @param options Options object for the route.
+   */
+  setOptions<Options extends object = object>(options: Options): void;
 } & PrivateValueStore<ParamList>;
 
 export type RouteProp<

src/useDescriptors.tsx

@@ -36,6 +36,7 @@ export default function useDescriptors<ScreenOptions extends object>({
   removeActionListener,
   onRouteFocus,
 }: Options) {
+  const [options, setOptions] = React.useState<{ [key: string]: object }>({});
   const context = React.useMemo(
     () => ({
       navigation,
@@ -67,6 +68,7 @@ export default function useDescriptors<ScreenOptions extends object>({
                 screen={screen}
                 getState={getState}
                 setState={setState}
+                setOptions={setOptions}
               />
             </NavigationBuilderContext.Provider>
           );
@@ -79,6 +81,7 @@ export default function useDescriptors<ScreenOptions extends object>({
                 navigation,
               })
             : screen.options),
+          ...options[route.key],
         },
       };
       return acc;

src/useOptions.tsx

@@ -0,0 +1,9 @@
+import useNavigation from './useNavigation';
+
+export default function useOptions<Options extends object = object>(
+  options: Options
+) {
+  const navigation = useNavigation();
+
+  navigation.setOptions<Options>(options);
+}