React-native: 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 :)

[rh389]

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.
https://github.com/facebook/react-native/pull/11797
https://github.com/facebook/react-native/pull/11798
https://github.com/facebook/react-native/pull/11799

[rh389]

https://github.com/facebook/react-native/pull/11806 and https://github.com/facebook/react-native/pull/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.

[janicduplessis]

Thanks a lot for working on this :)

[almadsen]

Ok so in latest release, 0.41 warnings are still there.
So basically my question now is if it's something I should worry about, or should I just try to mute them out?

[janicduplessis]

Most of them are fixed in master, I think these commits didn't make it to 0.41 sadly. You can just ignore them.

[rh389]

@janicduplessis I'd appreciate your thoughts on the last one remaining (last I checked). sendDeviceEventWithName is deprecated, apparently RCTUIManager should switch to module-scoped events instead. That in itself would be a small BC but probably acceptable.

The messy part is that this would diverge from the way Android emits the same events. AFAIK Android has no similar mechanism for module emitters and everything's global there. So the listening side, Dimensions , for example, would have to fork by platform, and must be aware of UIManager

If global events are genuinely deprecated (ie, will be removed) in iOS then this is something we've just got to do, and hopefully Android will catch up some day. If global events are going to hang around for a while yet, we might be better suppressing this warning until there's an Android equivalent. Or do we just take the plunge now and accept a bit of inconsistency?

[joshjhargreaves]

Hey, @rh389, @janicduplessis does this seem sensible?

[joemckie]

@janicduplessis I'm still getting very similar errors in 0.43.2. Is this still a valid issue?

[ndbroadbent]

@janicduplessis If I sent a pull request to remove all of these deprecation warnings, how long might it take for that to be accepted?

(I noticed there's an enormous number of issues and pull requests, so I'm worried about wasting my time if it never gets any attention.)

[rh389]

I think the only outstanding deprecation already has a PR https://github.com/facebook/react-native/pull/12209.

Many of the unused param warnings only appear in release builds because they're due to debug checks that get preprocessed away. I guess it should be possible to suppress that warning via a compiler setting for release only.

[ndbroadbent]

@rh389 Ah great, thanks.

Yeah that would be great if they could be suppressed. There's a lot of noise when I build the project in Xcode, and I have to scroll down a long way to see the actual errors.

[joshjhargreaves]

@ndbroadbent, you can actually filter to show only errors and not warnings in XCode.

It's the second icon on the right.

[hramos]

Hi there! This issue is being closed because it has been inactive for a while. Maybe the issue has been fixed in a recent release, or perhaps it is not affecting a lot of people. Either way, we're automatically closing issues after a period of inactivity. Please do not take it personally!

If you think this issue should definitely remain open, please let us know. The following information is helpful when it comes to determining if the issue should be re-opened:

• Does the issue still reproduce on the latest release candidate? Post a comment with the version you tested.
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• Is there a pull request that addresses this issue? Post a comment with the PR number so we can follow up.

If you would like to work on a patch to fix the issue, contributions are very welcome! Read through the contribution guide, and feel free to hop into #react-native if you need help planning your contribution.

[leonardpauli]

This issue is still valid, actually, I got closer to 100 warnings and a couple of "Logic errors" - from a fresh install! Those are noisy when trying to develop native components.

@rh389 said many where due to automatic release pre-processing. To suppress these warning - ONLY ON THE REACT STUFF - ie. not on your own code; change build settings for the relevant targets:

https://stackoverflow.com/questions/7997636/disable-warnings-in-xcode-from-frameworks

for the logic errors; see "-Xanalyzer -analyzer-disable-all-checks"

[vynogradskyi]

Confirm this issue still appears on React-Native "0.55.4". 170 warnings

[hramos]

Please give 0.56.0-rc a try - this is specifically called out in the changelog.