react / react/react-native

regression: VirtualizedList scrolls infinitely on new item

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Component: VirtualizedList Impact: Regression Issue: Author Provided Repro
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Description

Description

FlatList is behaving unexpectedly on React Native 0.71 for lists with dynamic height items.
I was able to create a repro pointing to React Native versions:

  • 0.69.8
  • 0.70.13
  • 0.71.12
  • 0.72.3

The issue starts to happen on 0.71, but it still happens on 0.72.
Bug happens both on Android and iOS.
I was not able to find the commit that introduced this bug.

React Native Version

0.72.3

Output of npx react-native info

System:
OS: macOS 13.0.1
CPU: (8) arm64 Apple M1 Pro
Memory: 88.42 MB / 16.00 GB
Shell:
version: 5.8.1
path: /bin/zsh
Binaries:
Node:
version: 18.15.0
path: ~/.nvm/versions/node/v18.15.0/bin/node
Yarn:
version: 1.22.19
path: /opt/homebrew/bin/yarn
npm:
version: 9.5.0
path: ~/.nvm/versions/node/v18.15.0/bin/npm
Watchman:
version: 2023.07.10.00
path: /opt/homebrew/bin/watchman
Managers:
CocoaPods:
version: 1.12.1
path: /Users/diegomello/.rvm/gems/ruby-2.7.7/bin/pod
SDKs:
iOS SDK:
Platforms:
- DriverKit 22.1
- iOS 16.1
- macOS 13.0
- tvOS 16.1
- watchOS 9.1
Android SDK:
API Levels:
- "23"
- "28"
- "30"
- "31"
- "33"
Build Tools:
- 23.0.1
- 23.0.2
- 25.0.0
- 25.0.1
- 25.0.2
- 25.0.3
- 26.0.1
- 26.0.2
- 26.0.3
- 27.0.1
- 27.0.3
- 28.0.3
- 29.0.0
- 29.0.1
- 29.0.2
- 29.0.3
- 30.0.2
- 30.0.3
- 31.0.0
- 33.0.0
System Images:
- android-27 | Google APIs ARM 64 v8a
- android-27 | Google Play Intel x86 Atom
- android-30 | Google Play ARM 64 v8a
- android-30 | Google Play Intel x86 Atom
- android-31 | ARM 64 v8a
- android-31 | Google APIs Intel x86 Atom_64
- android-31 | Google Play ARM 64 v8a
Android NDK: 23.0.7344513-beta4
IDEs:
Android Studio: 2022.2 AI-222.4459.24.2221.9862592
Xcode:
version: 14.1/14B47b
path: /usr/bin/xcodebuild
Languages:
Java:
version: 11.0.18
path: /usr/bin/javac
Ruby:
version: 2.7.7
path: /Users/diegomello/.rvm/rubies/ruby-2.7.7/bin/ruby
npmPackages:
"@react-native-community/cli": Not Found
react:
installed: 18.2.0
wanted: 18.2.0
react-native:
installed: 0.72.3
wanted: 0.72.3
react-native-macos: Not Found
npmGlobalPackages:
"react-native": Not Found
Android:
hermesEnabled: false
newArchEnabled: false
iOS:
hermesEnabled: true
newArchEnabled: false

Steps to reproduce

See the video. The repro is very straightforward and it simulates a FlatList with dynamic height items.
It's all about scrolling until the list struggles to render the elements. (It's still stuck scrolling as I type the report)
I found it easier to scroll to around 800~1000 and tap Add item top, but it can be reproduced by just scrolling.

https://github.com/facebook/react-native/assets/804994/05787d61-dccf-4e36-8ee9-94a0c84236bd

(I trimmed the video to fit Github, but it was basically scrolling until it reached 1000 rows)

Snack, screenshot, or link to a repository

https://github.com/diegolmello/ReproListScroll

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with the linked ReproListScroll repository and reproduce the behavior described in the video, comparing React Native 0.70.13 with 0.71 and 0.72. Done means a FlatList with dynamic-height items no longer scrolls indefinitely or becomes stuck after adding an item near the top.

Written by the indexing model from the issue text.

Assessment

Tech stack
react-native
Domain
mobile
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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