Version 0.40.0 gives 12 issues in xcode

[almadsen]

Straight from init a new project and opening it with Xcode and running it in the iOS simulator I get 12 issues in Xcode, and this is without changing any code.

Did not get any issues with version 0.39.0

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• React Native version: 0.40.0
• Platform: iOS
• Operating System: MacOS

[andreencar]

Maybe some modules are affected by this?
https://github.com/facebook/react-native/releases/tag/v0.40.0

[almadsen]

No modules, I get this straight from initializing the project, so it's clean. No code changed, no modules, nothing. This is the files originally created.

[chirag04]

Those are warning and you can mostly ignore those warning. You project should run fine with those warning.

[janicduplessis]

It would be great if someone can send a PR to fix those warning, from the screenshot it seems pretty straightforward.

[LiuC520]

also these problems? when i use 0.40, some third packages are wrong

[neilsarkar]

For the RCTExecuteOnMainThread warnings, the deprecation warning states:

RCT_EXTERN void RCTExecuteOnMainThread(dispatch_block_t block, BOOL sync)
__deprecated_msg("Use RCTExecuteOnMainQueue instead. RCTExecuteOnMainQueue is "
                 "async. If you need to use the `sync` option... please don't.");

the two uses that are generating warnings are in RCTUtils.m and are low level functions for getting screen scale and size -- they both have many callers that expect a synchronous method signature.

// RCTUtils.m

CGFloat RCTScreenScale()
{
  static CGFloat scale;
  static dispatch_once_t onceToken;
  dispatch_once(&onceToken, ^{
    RCTExecuteOnMainThread(^{
      scale = [UIScreen mainScreen].scale;
    }, YES);
  });

  return scale;
}

CGSize RCTScreenSize()
{
  // FIXME: this caches the bounds at app start, whatever those were, and then
  // doesn't update when the device is rotated. We need to find another thread-
  // safe way to get the screen size.

  static CGSize size;
  static dispatch_once_t onceToken;
  dispatch_once(&onceToken, ^{
    RCTExecuteOnMainThread(^{
      size = [UIScreen mainScreen].bounds.size;
    }, YES);
  });

  return size;
}

I understand why we don't want to make synchronous calls on the main thread. Is this an exception? Would the preferred approach be to dispatch directly from these two functions instead of using the deprecated function? Or is the solution to refactor all callers to handle an asynchronous method signature?

[janicduplessis]

In this case we might want to silence the warning since there isn't an alternative to this.

[janicduplessis]

Another option (maybe better) would be to create RCTExecuteOnMainQueueSync that does what RCTExecuteOnMainThread(block, YES) does. RCTExecuteOnMainQueueSync could have a comment that says you shouldn't use it unless you know what you are doing.

[neilsarkar]

Thanks for the info @janicduplessis.

It's 2am in Portugal so I'm gonna call it for tonight but will implement this suggestion and submit tomorrow, although I'm not sure the issue will still be there by then judging by the trajectory @rh389 is on with these warnings :)

[robhogan]

Haha I'm also about to call it a night (UK) - I'll leave the RCTExecuteOnMainThread warnings to you as I was unsure how to handle those myself. The event dispatcher one is also tricky since switching to a scoped event would be a BC.

Some progress though - if these go through it's 8 down, 4 to go.
#11797
#11798
#11799

[robhogan]

#11806 and #11807 just leaves the RCTExecuteOnMainThread and sendDeviceEventWIthName deprecation warnings.

I'm going to take a break for now and do something I'm paid for ;). Will revisit this in a day or two if there's still anything outstanding.