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Make PlatformConstants use main queue setup (#50111) #50141

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@RSNara RSNara commented Mar 19, 2025

Summary:

Rationale

Rendering can now include main -> js sync calls.

If we allow js -> main sync calls during rendering, react native can deadlock.

So, this diff moves the js -> main sync calls to "main queue module setup", which occurs before rendering.

Changelog: [Internal]

Differential Revision: D71480047

RSNara added 3 commits March 19, 2025 09:22
…#49957)

Summary:
Pull Request resolved: facebook#49957

## Changes
This diff introduces the api for "main queue modules" into turbo modules.

This will occur occurs before any rendering.

## Rationale

Rendering can now include main -> js sync calls. If we allow js -> main sync calls during rendering, react native can deadlock.

With this diff, we can move the js -> main sync calls to before any rendering happens.

## APIs
**Buck API:**
Plugin:
```
react_module_plugin_providers(
    name = "AccessibilityManager",
    native_class_func = "RCTAccessibilityManagerCls",
    unstable_requires_main_queue_setup = True,
)
```

**OSS API:**
[codegenConfig](https://reactnative.dev/docs/the-new-architecture/using-codegen) in package.json:
```
"codegenConfig": {
    "name": "<SpecName>",
    "type": "<types>",
    "jsSrcsDir": "<source_dir>",
    "android": {
      "javaPackageName": "<java.package.name>"
    },
    "ios": {
      "modules": {
        "AccessibilityManager": {
          "className": "RCTAccessibilityManager",
          "unstableRequiresMainQueueSetup": true
         }
      }
    }
  },
```

Changelog: [iOS][Added] Introduce unstableRequiresMainQueueSetup api to modules

Differential Revision: D70413478

Reviewed By: cipolleschi
…#50040)

Summary:
Pull Request resolved: facebook#50040

This diff implements main queue module setup.

Sometimes, people need to capture uikit things, and use them from javascript. In those cases, people can write main queue modules. These modules will be eagerly initialized on the main queue, during react native init.

## On Necessity
**Sync** dispatches to the main thread from the js thread can deadlock react native. And **async** dispatches to the main thread from the js thread sometimes might not be enough: it could lead to flickery rendering. So, we need to allow people to capture ui thread things, before any js executes.

## Caveat
This api is dangerous and discouraged. All react native surfaces will pay the cost of one surface introducing a main queue module. It could also slow down common/critical interactions in your app, if you're not careful.

We will introduce performance logging for this infrastructure. So that we can monitor and file tasks, when main queue module init starts taking "too long."

Changelog: [General][Breaking]: Introduce beforeload callback arg into ReactInstance::loadScript

Differential Revision: D71084243

Reviewed By: mdvacca
Summary:
We will use main queue setup of native modules to solve this problem instead.

Changelog: [Internal]

Differential Revision: D71341038

Reviewed By: mdvacca
@facebook-github-bot facebook-github-bot added CLA Signed This label is managed by the Facebook bot. Authors need to sign the CLA before a PR can be reviewed. p: Facebook Partner: Facebook Partner labels Mar 19, 2025
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This pull request was exported from Phabricator. Differential Revision: D71480047

Summary:
Pull Request resolved: facebook#50141

Pull Request resolved: facebook#50111

## Rationale
Rendering can now include main -> js sync calls.

If we allow js -> main sync calls during rendering, react native can deadlock.

So, this diff moves the js -> main sync calls to "main queue module setup", which occurs before rendering.

Changelog: [Internal]

Reviewed By: mdvacca

Differential Revision: D71480047
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This pull request was exported from Phabricator. Differential Revision: D71480047

@RSNara RSNara force-pushed the export-D71480047 branch from f1ebeda to d7c8729 Compare March 19, 2025 21:19
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