React-native: RCTRootView: updating appProperties does not work on iOS if bridge is still loading

[teameh]

• [x] Review the documentation: https://facebook.github.io/react-native
• [x] Search for existing issues: https://github.com/facebook/react-native/issues
• [x] Use the latest React Native release: https://github.com/facebook/react-native/releases

Environment

Scanning folders for symlinks in /Users/veen011/Projects/Apps/AppPropertiesNoReRenderWhileBridgeIsLoading/node_modules (13ms)

  React Native Environment Info:
    System:
      ### Please let me know if you need this ###
    Binaries:
      Node: 10.5.0 - /usr/local/bin/node
      Yarn: 1.7.0 - /usr/local/bin/yarn
      npm: 6.1.0 - /usr/local/bin/npm
      Watchman: 4.9.0 - /usr/local/bin/watchman
    SDKs:
      iOS SDK:
        Platforms: iOS 11.4, macOS 10.13, tvOS 11.4, watchOS 4.3
    IDEs:
      Android Studio: 3.1 AI-173.4819257
      Xcode: 9.4.1/9F2000 - /usr/bin/xcodebuild
    npmPackages:
      react: 16.4.1 => 16.4.1
      react-native: 0.56.0 => 0.56.0

Short description

Follow up on https://github.com/facebook/react-native/issues/15938

Relevant documentation:

RCTRootView also provides a read-write property appProperties. After appProperties is set, the React Native app is re-rendered with new properties. The update is only performed when the new updated properties differ from the previous ones.
{...}
It is fine to update properties anytime. However, updates have to be performed on the main thread. You use the getter on any thread.

This is not the case, the app is not re-rendered if the bridge was still loading when the properties are updated.

Reproducible Demo

git clone [email protected]:teameh/AppPropertiesNoReRenderWhileBridgeIsLoading.git
cd AppPropertiesNoReRenderWhileBridgeIsLoading
react-native run-ios

or

• create new RN app (react-native init MyProject)
• apply this commit https://github.com/teameh/AppPropertiesNoReRenderWhileBridgeIsLoading/commit/981e953d45ff440bf4dde6bc24100a41822e53ec
• react-native run-ios

The only change I made to the sample project is adding and updating some some props of the view:

    RCTRootView *rootView = [[RCTRootView alloc] initWithBundleURL:jsCodeLocation
                                                       moduleName:@"AppPropertiesNoReRenderWhileBridgeIsLoading"
-                                               initialProperties:nil
+                                               initialProperties:@{@"foo" : @"bar"}
                                                    launchOptions:launchOptions];
+
+  rootView.appProperties = @{@"foo" : @"qux"};

Which are used in the RN view:

<Text style={styles.welcome}>"{this.props.foo}"</Text>

Before reloading the project the 3rd text node on the view should display "qux" if it displays "bar" it means the props have not been updated.

[teameh]

I did some more digging and I think this is caused by the following:

• In RCTRootView's initWithBridge method bundleFinishedLoading is always called even though the javascript might still be loading..

• bundleFinishedLoading calls runApplication:bridge with the initial properties.

• An instant later, when setAppProperties is called (and normally the app runs again) the bridge is still loading so the app won't run again:

- (void)setAppProperties:(NSDictionary *)appProperties
{
  RCTAssertMainQueue();

  if ([_appProperties isEqualToDictionary:appProperties]) {
    return;
  }

  _appProperties = [appProperties copy];

  if (_contentView && _bridge.valid && !_bridge.loading) {
    [self runApplication:_bridge];
  }
}

• Somewhere after this the loading of the javascript completes and javaScriptDidLoad is called. But the bridge is the same and thus bundleFinishedLoading won't get called again, preventing the update:

- (void)javaScriptDidLoad:(NSNotification *)notification
{
  RCTAssertMainQueue();

  // Use the (batched) bridge that's sent in the notification payload, so the
  // RCTRootContentView is scoped to the right bridge
  RCTBridge *bridge = notification.userInfo[@"bridge"];
  if (bridge != _contentView.bridge) {
    [self bundleFinishedLoading:bridge];
  }
}

[teameh]

Tried to write some code that fixes this, see the PR.

[teameh]

Is there anything I can do to help fix this issue? No worries, I understand that it's hard to maintain a repo with 600+ open issues :)

[jessedijkstra]

I'm having the same issue, any updates?

[harking]

Until this is fixed, a workaround is to listen to the RCTJavaScriptDidLoad and set the appProperties in there.
```swift
NotificationCenter.default.addObserver(forName: NSNotification.Name.RCTJavaScriptDidLoad, object: nil, queue: nil) {
[weak self] _ in
self?.setAppProperties()
}

[jessedijkstra]

@cpojer The issue has been closed, does that mean that this bug has been fixed?

[jeremyis]

I think I am still experiencing this issue. The Objective C code is slightly different:

[[NSNotificationCenter defaultCenter] addObserverForName:RCTJavaScriptDidLoadNotification object:nil queue:nil usingBlock:^(NSNotification * _Nonnull note) {

}];

[zbagley]

@jessedijkstra This is a react native repo, which means they close bugs whenever they want because otherwise they'd have too many to ever actually fix ;) Need to use the workaround.

[imcodingideas]

This is even something they know because its references here: https://facebook.github.io/react-native/docs/communication-ios on the docs.