Merge pull request Expensify#84002 from Expensify/claude-fixNativeOnTabSelectOnMount

Fix: Patch PagerViewAdapter to call onTabSelect on initial mount for native

Author: Gonals

patches/react-native-tab-view/details.md

@@ -34,3 +34,14 @@
 - Upstream PR/issue: 🛑 (must merge https://github.com/react-navigation/react-navigation/pull/12627 first)
 - E/App issue: https://github.com/Expensify/App/issues/71913#issuecomment-3584103273
 - PR Introducing Patch: [#76586](https://github.com/Expensify/App/pull/76586)
+
+### [react-native-tab-view+4.1.0+004+fix-native-onTabSelect-on-mount.patch](react-native-tab-view+4.1.0+004+fix-native-onTabSelect-on-mount.patch)
+
+- Reason:
+    ```
+    This patch fixes an issue on iOS native where the `onTabSelect` callback was not being called on initial mount
+    in the PagerViewAdapter. This mirrors the web fix from patch 003 (PanResponderAdapter) and ensures the input
+    field is auto-focused when opening the Start Chat screen on iOS.
+    ```
+- Upstream PR/issue: 🛑 (must merge https://github.com/react-navigation/react-navigation/pull/12627 first)
+- E/App issue: https://github.com/Expensify/App/issues/83010

patches/react-native-tab-view/react-native-tab-view+4.1.0+004+fix-native-onTabSelect-on-mount.patch

@@ -0,0 +1,26 @@
+diff --git a/node_modules/react-native-tab-view/src/PagerViewAdapter.tsx b/node_modules/react-native-tab-view/src/PagerViewAdapter.tsx
+index d66b0cb..a1b2c3d 100644
+--- a/node_modules/react-native-tab-view/src/PagerViewAdapter.tsx
++++ b/node_modules/react-native-tab-view/src/PagerViewAdapter.tsx
+@@ -57,3 +57,5 @@ export function PagerViewAdapter<T extends Route>({
+   const pagerRef = React.useRef<ViewPager>(null);
+   const indexRef = React.useRef<number>(index);
+   const navigationStateRef = React.useRef(navigationState);
++  const onTabSelectRef = React.useRef(onTabSelect);
++  const hasCalledInitialTabSelectRef = React.useRef(false);
+@@ -64,3 +66,15 @@ export function PagerViewAdapter<T extends Route>({
+   React.useEffect(() => {
+     navigationStateRef.current = navigationState;
++    onTabSelectRef.current = onTabSelect;
+   });
++
++  React.useEffect(() => {
++    if (hasCalledInitialTabSelectRef.current) {
++      return;
++    }
++    hasCalledInitialTabSelectRef.current = true;
++    // Call onTabSelect on initial mount (parity with web PanResponderAdapter patch)
++    requestAnimationFrame(() => {
++      onTabSelectRef.current?.({index: navigationStateRef.current.index});
++    });
++  }, []);