From f516080e6e9735ca993866d5c7aa4c0b5fc52e90 Mon Sep 17 00:00:00 2001
From: Mateusz Wit <maateew@gmail.com>
Date: Wed, 10 Jul 2024 20:06:04 +0200
Subject: [PATCH] fix(#814): update sticky headers when data changes without
 changing stickyHeaderIndices updated

---
 CHANGELOG.md                                |   3 +
 fixture/react-native/src/ExamplesScreen.tsx |   1 +
 fixture/react-native/src/NavigationTree.tsx |   2 +
 fixture/react-native/src/SectionList.tsx    | 189 ++++++++++++++++++++
 fixture/react-native/src/constants.ts       |   1 +
 src/FlashList.tsx                           |   4 +-
 6 files changed, 199 insertions(+), 1 deletion(-)
 create mode 100644 fixture/react-native/src/SectionList.tsx

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9ead4ed31..43a541d3a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,9 @@ and adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
 
+- Fix first sticky header is not rendering when data changed
+  - https://github.com/Shopify/flash-list/issues/814
+
 ## [1.7.0] - 2024-07-03
 
 - Update internal dependency and fixture app to `react-native@0.72`.
diff --git a/fixture/react-native/src/ExamplesScreen.tsx b/fixture/react-native/src/ExamplesScreen.tsx
index 1e9f04144..ed473ef77 100644
--- a/fixture/react-native/src/ExamplesScreen.tsx
+++ b/fixture/react-native/src/ExamplesScreen.tsx
@@ -21,6 +21,7 @@ export const ExamplesScreen = () => {
 
   const data: ExampleItem[] = [
     { title: "List", destination: "List" },
+    { title: "SectionList", destination: "SectionList" },
     { title: "PaginatedList", destination: "PaginatedList" },
     { title: "Reminders", destination: "Reminders" },
     { title: "Twitter Timeline", destination: "Twitter" },
diff --git a/fixture/react-native/src/NavigationTree.tsx b/fixture/react-native/src/NavigationTree.tsx
index 5288683f1..22789d032 100644
--- a/fixture/react-native/src/NavigationTree.tsx
+++ b/fixture/react-native/src/NavigationTree.tsx
@@ -15,6 +15,7 @@ import { Messages, MessagesFlatList } from "./Messages";
 import TwitterBenchmark from "./twitter/TwitterBenchmark";
 import TwitterCustomCellContainer from "./twitter/CustomCellRendererComponent";
 import { Masonry } from "./Masonry";
+import { SectionList } from "./SectionList";
 
 const Stack = createStackNavigator<RootStackParamList>();
 
@@ -25,6 +26,7 @@ const NavigationTree = () => {
         <Stack.Group>
           <Stack.Screen name="Examples" component={ExamplesScreen} />
           <Stack.Screen name="List" component={List} />
+          <Stack.Screen name="SectionList" component={SectionList} />
           <Stack.Screen name="PaginatedList" component={PaginatedList} />
           <Stack.Screen name="Twitter" component={Twitter} />
           <Stack.Screen name="Reminders" component={Reminders} />
diff --git a/fixture/react-native/src/SectionList.tsx b/fixture/react-native/src/SectionList.tsx
new file mode 100644
index 000000000..e7187550d
--- /dev/null
+++ b/fixture/react-native/src/SectionList.tsx
@@ -0,0 +1,189 @@
+/** *
+ Use this component inside your React Native Application.
+ A scrollable list with different item type
+ */
+import React, { useMemo, useRef, useState } from "react";
+import {
+  View,
+  Text,
+  Pressable,
+  LayoutAnimation,
+  StyleSheet,
+} from "react-native";
+import { FlashList, ListRenderItemInfo } from "@shopify/flash-list";
+
+const generateItemsArray = (size: number) => {
+  const arr = new Array(size);
+  for (let i = 0; i < size; i++) {
+    arr[i] = i;
+  }
+  return arr;
+};
+
+const generateSectionsData = (size: number, index = 0) => {
+  const arr = new Array<{ index: number; data: number[] }>(size);
+  for (let i = 0; i < size; i++) {
+    arr[i] = {
+      index: index + i,
+      data: generateItemsArray(10),
+    };
+  }
+  return arr;
+};
+
+interface Section {
+  type: "section";
+  index: number;
+}
+
+interface Item {
+  type: "item";
+  index: number;
+  sectionIndex: number;
+}
+
+type SectionListItem = Section | Item;
+
+export const SectionList = () => {
+  const [refreshing, setRefreshing] = useState(false);
+  const [sections, setSections] = useState(generateSectionsData(10));
+
+  const list = useRef<FlashList<SectionListItem> | null>(null);
+
+  const flattenedSections = useMemo(
+    () =>
+      sections.reduce<SectionListItem[]>((acc, { index, data }) => {
+        const items: Item[] = data.map((itemIndex) => ({
+          type: "item",
+          index: itemIndex,
+          sectionIndex: index,
+        }));
+
+        return [...acc, { index, type: "section" }, ...items];
+      }, []),
+    [sections]
+  );
+
+  const stickyHeaderIndices = useMemo(
+    () =>
+      flattenedSections
+        .map((item, index) => (item.type === "section" ? index : undefined))
+        .filter((item) => item !== undefined) as number[],
+    [flattenedSections]
+  );
+
+  const removeItem = (item: Item) => {
+    setSections(
+      sections.map((section) => ({
+        ...section,
+        data: section.data.filter((index) => index === item.index),
+      }))
+    );
+    list.current?.prepareForLayoutAnimationRender();
+    // after removing the item, we start animation
+    LayoutAnimation.configureNext(LayoutAnimation.Presets.easeInEaseOut);
+  };
+
+  const removeSection = () => {
+    setSections(sections.slice(1));
+    list.current?.prepareForLayoutAnimationRender();
+    // after removing the item, we start animation
+    LayoutAnimation.configureNext(LayoutAnimation.Presets.easeInEaseOut);
+  };
+
+  const addSection = () => {
+    const lastIndex = sections[sections.length - 1].index;
+    setSections([...sections, ...generateSectionsData(1, lastIndex + 1)]);
+    list.current?.prepareForLayoutAnimationRender();
+    // after removing the item, we start animation
+    LayoutAnimation.configureNext(LayoutAnimation.Presets.easeInEaseOut);
+  };
+
+  const renderItem = ({ item }: ListRenderItemInfo<SectionListItem>) => {
+    if (item.type === "section") {
+      return (
+        <View
+          style={{
+            ...styles.container,
+            backgroundColor: "purple",
+            width: "100%",
+            height: 30,
+          }}
+        >
+          <Text>Section: {item.index}</Text>
+        </View>
+      );
+    }
+
+    const backgroundColor = item.index % 2 === 0 ? "#00a1f1" : "#ffbb00";
+
+    return (
+      <Pressable onPress={() => removeItem(item)}>
+        <View
+          style={{
+            ...styles.container,
+            backgroundColor: item.index > 97 ? "red" : backgroundColor,
+            height: item.index % 2 === 0 ? 100 : 200,
+          }}
+        >
+          <Text>
+            Section: {item.sectionIndex} Cell Id: {item.index}
+          </Text>
+        </View>
+      </Pressable>
+    );
+  };
+
+  return (
+    <>
+      <View style={styles.buttonsContainer}>
+        <Pressable onPress={addSection}>
+          <View style={styles.button}>
+            <Text>Add Section</Text>
+          </View>
+        </Pressable>
+        <Pressable onPress={removeSection}>
+          <View style={styles.button}>
+            <Text>Remove Section</Text>
+          </View>
+        </Pressable>
+      </View>
+
+      <FlashList
+        ref={list}
+        refreshing={refreshing}
+        onRefresh={() => {
+          setRefreshing(true);
+          setTimeout(() => {
+            setRefreshing(false);
+          }, 2000);
+        }}
+        keyExtractor={(item) =>
+          item.type === "section"
+            ? `${item.index}`
+            : `${item.sectionIndex}${item.index}`
+        }
+        renderItem={renderItem}
+        estimatedItemSize={100}
+        stickyHeaderIndices={stickyHeaderIndices}
+        data={flattenedSections}
+      />
+    </>
+  );
+};
+
+const styles = StyleSheet.create({
+  container: {
+    justifyContent: "space-around",
+    alignItems: "center",
+    height: 120,
+    backgroundColor: "#00a1f1",
+  },
+  buttonsContainer: {
+    flexDirection: "row",
+    justifyContent: "space-around",
+  },
+  button: {
+    padding: 10,
+  },
+});
diff --git a/fixture/react-native/src/constants.ts b/fixture/react-native/src/constants.ts
index d27d7b700..7a2b82627 100644
--- a/fixture/react-native/src/constants.ts
+++ b/fixture/react-native/src/constants.ts
@@ -5,6 +5,7 @@ import { TweetContentProps } from "./twitter/TweetContent";
 export type RootStackParamList = {
   Examples: undefined;
   List: undefined;
+  SectionList: undefined;
   Reminders: undefined;
   PaginatedList: undefined;
   Twitter: undefined;
diff --git a/src/FlashList.tsx b/src/FlashList.tsx
index fa851f0db..bf08642fb 100644
--- a/src/FlashList.tsx
+++ b/src/FlashList.tsx
@@ -693,7 +693,7 @@ class FlashList<T> extends React.PureComponent<
 
   private stickyOverrideRowRenderer = (
     _: any,
-    __: any,
+    rowData: any,
     index: number,
     ___: any
   ) => {
@@ -701,6 +701,8 @@ class FlashList<T> extends React.PureComponent<
       <PureComponentWrapper
         ref={this.stickyContentRef}
         enabled={this.isStickyEnabled}
+        // We're passing rowData to ensure that sticky headers are updated when data changes
+        rowData={rowData}
         arg={index}
         renderer={this.rowRendererSticky}
       />