Andrei Calazans

React Native Weekly Special - Weeks 7, 8, and 9 2022

☕️☕️ 12 min read

This is the 44th edition of the React Native Weekly, and this edition comes after a two weeks hiatus where I struggled to find the energy to work on the RN weekly - send positive vibes ❤️.

This edition covers 7th to 27th of February, a wopping 20 days of commits 😲 - 139 commits by 44 distinct engineers.

In this edition I did not include any community updates due to the size of the post.


  • React Native New Architecture Working Group
  • Fix incorrect border color when switching to dark mode [iOS]
  • Fix broken input for Korean alphabet in TextInput [iOS]
  • Fix action sheet callback invoked more than once on iPad
  • Fix Text with adjustFontSizeToFit updating infinitely [Android]
  • Removed script
  • Flag to build Hermes from source on iOS
  • Synchronously render cached images [iOS]

And more…

Fix TouchableOpacity not reacting to dynamic style.opacity changes

Hetan Thakkar posted the issue and sent a fix. With this fix dynamically changing the opacity style will also trigger the TouchableOpacity’s inactive state.

Rename RuntimeScheduler::callImmediates to RuntimeScheduler::callExpiredTasks

The compeling part of this change is the comment to visualize the upcoming concurrent mode and how React Native renderer will handle it through the RuntimeScheduler.

+   * Expired task is a task that should have been already executed. Designed to
+   * be called in the event pipeline after an event is dispatched to React.
+   * React may schedule events with immediate priority which need to be handled
+   * before the next event is sent to React.
    * Thread synchronization must be enforced externally.
-  void callImmediates(jsi::Runtime &runtime);
+  void callExpiredTasks(jsi::Runtime &runtime);

along side the above change Samuel Susla also enabled RuntimeScheduler::callExpiredTasks on Android.

Fix incorrect border color when switching to dark mode [iOS]

Danilo Bürger fixed an issue that was a side-effect to prior change that started using the system UIColor on iOS instead of the CGColor for the borders, see this link for the difference.

Danilo noticed how in certain iOS OS versions it did not resolve the correct border color for dark mode, see related StackOverflow post. This commit resolves the colors with the current trait collection to ensure the right colors are selected.

Update RedBoxDialog to separate content view and dialog

Xin Chen made a strategic change due to VR.

Summary from Xin:

This diff separates the content view creation logic from existing RedBoxDialog logic. After the change, RedBoxDialog is no longer a subclass of Dialog, but behaves like a dialog with forwarding pattern to delegate dialog API to internal member. This will keep the APIs consistent with dependent components.

The motivation of the change is to make the content view reusable. This is important in VR surface where we don’t have activities and necessary implementations for Dialog to show.

He later also created a delegate - RedBoxSurfaceDelegate to abstract the surface logic on how to show RedBox.

Introduce RawEventEmitter

Joshua Gross added the RawEventEmitter interface.

Further support for AnimatedColor

Genki Kondo continued the feature work to fully support AnimatedColor natively on both iOS and Android. The following were added during this period:

Next up Genki mentioned adding iOS support for platform colors.

Fix DarkMode for DatePickerDialogFragment [Android]

David Vacca fixed DarkMode on the Calendar DateTimePicker.

diff --git a/ReactAndroid/src/main/res/shell/values/styles.xml b/ReactAndroid/src/main/res/shell/values/styles.xml
index b0418ce8525..1db9ac70f79 100644
--- a/ReactAndroid/src/main/res/shell/values/styles.xml
+++ b/ReactAndroid/src/main/res/shell/values/styles.xml
@@ -19,11 +19,12 @@
         <item name="android:datePickerMode">spinner</item>
-    <style name="CalendarDatePickerDialog" parent="Theme.AppCompat.Light.Dialog" tools:targetApi="lollipop">
+    <style name="CalendarDatePickerDialog" parent="android:Theme.Material.Dialog.Alert" tools:targetApi="lollipop">
         <item name="android:datePickerStyle">@style/CalendarDatePickerStyle</item>
+        <item name="android:windowIsFloating">true</item>
-    <style name="CalendarDatePickerStyle" parent="android:Widget.Material.Light.DatePicker" tools:targetApi="lollipop">
+    <style name="CalendarDatePickerStyle" parent="android:Widget.Material.DatePicker" tools:targetApi="lollipop">
         <item name="android:datePickerMode">calendar</item>

Improved JVM 11 error message

Muhammad Numan improved the JVM error message due to trying to build Gradle with other than JVM 11 and Nicola Corti downgrade the Java source/target compat to JVM 8 for the invalid JVM version to be handled through a formatted message.

He added a check for the JVM version which outputs the following message:


ERROR: requires JDK11 or higher.
Incompatible major version detected: '8'


Fix bug when converting string casing with on non ASCII languages [Android]

Hamid added a fix for a very unexpected bug where lowering/upper casing a string in a non ASCII langugage like Turkish causes a bug by returning unexpected symbols, see joltup/rn-fetch-blob#573

The fix is suprisingly to add Locale.ROOT as argument to the toLowerCase or toUpperCase calls.

final String splitBundlesDir = subclassTag.toLowerCase(Locale.ROOT) + "_dev_js_split_bundles";

Fix broken input for Korean alphabet in TextInput [iOS]

Minsik Kim tackled a long standing issue where updating text in a TextView/TextField with Korean language had unexpected results.

Disable view flattening when the view has event handlers [Android]

Andrei Shikov added the following change, comment from Andrei Shikov:

The views with touch event props are currently flattened by Fabric core, as we don’t take event listeners into account when calculating whether the view should be flattened. This results in a confusing situation when components with touch event listeners (e.g. <View onTouchStart={() => {}} /> ) or ones using PanResponder are either ignored (iOS) or cause a crash (Android).

Bridgeless Mode Warnings

Paige Sun added a few error logs to warn of unexpected use of ReactInstanceManager or any deprecated methods in Bridgeless mode.

Deprecated methods/modules in bridgeless mode include ReactInstanceManager and all UIManager methods.

Fix RCTLogError and RCTLogWarn to display RedBox or LogBox in Bridgeless

Paige Sun fixed an issue with the native RCTLogError and RCTLogWarn to display RedBox or LogBox in Bridgeless mode for feature parity between Bridge and Bridgeless.

Added ability to access properties with symbol keys through JSI

Commit by Neil Dhar

Fix crash for some OS/OEM when WebView is not supported [Android]

Kunal Farmah fixed an issue where the error catch was not working due to inconsistent crash class name between OS/OEMs on Android. Instead Kunal resorted to parsing the error message for the right keywords - seems brittle, Android I guess.

Kunal explained how to reproduce this crash today:

Launch any app that has a webview. Go to settings->apps->Android System Webview -> disable. Resume/Restart the app.

In this fix: Open a webview and notice that the app will not crash.

In current version: App crashes on startup as the exception escapes the catch block. Even if it survives startup (did on Realme X), it will crash once you try to open a webview.

Fixed accessibility announcement for disable state on press Text

Fix by fabriziobertoglio1987

Fix ReactHorizontalScrollView contentOffset

Genki Kondo brought the same fix for ReactScrollView to ReactHorizontalScrollView.

According to Genki:

When setting ScrollView’s contentOffset, if the ScrollView hasn’t been laid out yet when ReactHorizontalScrollViewManager.setContentOffset is called, then scroll position is never set properly. This is because the actual scroll offset (0, 0) was being passed into setPendingContentOffsets, instead of the desired scroll offset. Thus, when ReactHorizontalScrollView.onLayout gets called, ReactHorizontalScrollView.scrollTo gets called with (0, 0).

Refactor Fabric Perf Logger

David Vacca refactored the Fabric commit statistics to simplify and allow it to be consumed outside Fabric to be integrated by a developer tools in the future.

For those curious, here is the list of evet names caputured by this performance logger:

+    return name == FABRIC_COMMIT_START
+        || name == FABRIC_COMMIT_END
+        || name == FABRIC_DIFF_START
+        || name == FABRIC_DIFF_END
+        || name == FABRIC_LAYOUT_START
+        || name == FABRIC_LAYOUT_END
+        || name == FABRIC_BATCH_EXECUTION_END

Fix action sheet callback invoked more than once on iPad

Fix by Janic Duplessis

According to Janic:

iOS will sometimes invoke the UIAlertAction handler for the cancel button more than once on iPad. This can be reproduced relatively easily by having a button that opens an action sheet and spam tapping outside the action sheet while it is opening. Since native module callbacks can only be invoked once this causes the app to crash here

@react-native-community/viewpager is no longer supported

maaxg updated the reference to react-native-community/viewpager which is no longer supported, the recommendation it’s to use react-native-pager-view instead.

Support for setting up a Gradle Enterprise instance via external script

Nicola Corti added support to allow for setting up a Gradle Enterprise instance via an external script.

From Nicola:

This diff allows to setup a Gradle Enterprise instance either locally or on CI via an external Gradle script. I’ve create a .sample script that users can copy to start setting up their GE instance, should they have one. Moreover, it applies the com.gradle.enterprise Gradle plugin by default. This has the positive side effect of not invalidating build cache for the included build if you happen to pass the --scan flag in OSS (as the classpath isn’t changed).

Fixed Switch component not disabling clicks

fabriziobertoglio1987 fixed a state issue where the Switch component did not disable clicks when setting either disabled to true or accessibilityState?.disabled to true.

Unblock CI by disabling test_ios_unit_hermes

Nicola Corti had to disable the test_ios_unit_hermes CI test because the commit that extended JSI to support accessing properties with symbol keys broke iOS hermes due to an ABI incompatibility.

According to Nicola: We can re-enable them as soon as Hermes 0.12.0 is released.

Set build.gradle resolution to not mix React native imports

Nicola Corti set a resolution strategy for com.facebook.react:react-native when on New Architecture to not mix imports of React Native from source vs prebuilts.

According to Nicola:

With this resolution strategy, we’ll make sure all the import of com.facebook.react:react-native:+ will be resolved to the correct dependency.

diff --git a/template/android/app/build.gradle b/template/android/app/build.gradle
index 506dca12111..bb24740f14a 100644
--- a/template/android/app/build.gradle
+++ b/template/android/app/build.gradle
+if (isNewArchitectureEnabled()) {
+    // If new architecture is enabled, we let you build RN from source
+    // Otherwise we fallback to a prebuilt .aar bundled in the NPM package.
+    // This will be applied to all the imported transtitive dependency.
+    configurations.all {
+        resolutionStrategy.dependencySubstitution {
+            substitute(module("com.facebook.react:react-native"))
+                    .using(project(":ReactAndroid")).because("On New Architecture we're building React Native from source")
+        }
+    }

Diff was cut for shortness, see commit for full diff

Fix Text with adjustFontSizeToFit updating infinitely [Android]

Alfonso Curbelo fixed an issue where a text component that has the property adjustsFontSizeToFit updated the text layout infinitely on Android.

Deprecate reactRoot in favor of root and reactNativeDir [Gradle][Android]

Commit by Nicola Corti, worth reviewing this commit if you have a Monorepo and use reactRoot.

From Nicola:

The reactRoot property was confusing as we were using it for both the root of the project and the react-native NPM Package root. I’m deprecating it and splitting it in two.

I’ve added several warning in the codebase to tell the people how to migrate away from it. Moreover this is specifying default values that are more user-friendly. Users won’t have to configure anything unless they are in a monorepo.

Introduce ReactNativeFeatureFlags

David Vacca introduced ReactNativeFeatureFlags file to control FeatureFlags in React Native, currently it only controls isLayoutAnimationEnabled.

Removed script

Riccardo Cipolleschi removed the script because it introduced complexity to the system.

Warning - if you relied on to set your Node version using some Node Package Manager this will likely break your flow.

Enable Kotlin build in OSS

Commit by Andrei Shikov Could this mean we will start seeing some native modules in Kotlin? Maybe.

Use mapbuffer for ReactViewGroup [Android]

Another changy by Andrei Shikov, Andrei explains well his changes in his commit message:

Provides an alternative way of diffing props on Android side. Instead of passing dynamic JSON values from JS, the new approach diff C++ props and serializes difference into a MapBuffer. Current implementation does this only for RCTView component to test performance, correctness and memory impact (as MapBuffers are supposed to be more compact and performant).

This way of passing props allows for additional alignment between platforms, as C++ props are now source of truth for the view state, similar to iOS. At the same time, changing serialization method requires reimplementing ViewManager codegen (done manually for now) to account for MapBuffers.

With the above change, Andrei Shikov also optimized the rawProps variable to only initialize when not using MapBuffer potentially decreasing memory footprint.

Add flag to enable building Hermes from source on iOS

Commit by Héctor Ramos

With this change, you can run BUILD_HERMES_SOURCE=1 pod install to build Hermes from source on iOS.

Fix Switch causing RetryableMountingLayerException

Fix by jonathanmos


Added a null check to native.value in Switch to fix regression from RN 66 -> stuck operation in mViewCommandOperations list in Android Release on initial layout of a screen with Switch component. If approved, please incorporate this fix into an RN 66 release.

Implement ReadableNative*::mapException without dynamic_cast

Adapted from Pieter De Baets commit message, Pieter changed fbjni’s mapException interface to use std::exception_ptr, this enables the use of std::rethrow_exception and catch statements to check for specific exception types, rather than using dynamic_casts and having an explicit dependency on RTTI.

Note that avoiding RTTI provides significant binary size gains.

Synchronously render cached images [iOS]

Mo Wang noticed how React Native asynchronously loaded even cached images resulting in the image rendering a frame later. With this patch this no longer happens and the image renders synchronously.

Dependency bumps

React Native New Architecture Working Group

Similar to the React 18 working group that was created to discuss the roll out of React 18 with the community, the React Native Core team created a new architecture working group.


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