Run getConstants method statements on main queue

Summary:
If a NativeModule requires main queue setup, its `getConstants()` method must be executed on the main thead. The legacy NativeModule infra takes care of this for us. With TurboModules, however, all synchronous methods, including `getConstants()`, execute on the JS thread. Therefore, if a TurboModule requires main queue setup, and exports constants, we must execute its `getConstants()` method body on the main queue explicitly.

**Notes:**
- The changes in this diff should be a noop when TurboModules is off, because `RCTUnsafeExecuteOnMainQueueSync` synchronously execute its block on the current thread if the current thread is the main thread.
- If a NativeModule doens't have the `requiresMainQueueSetup` method, but has the `constantsToExport` method, both NativeModules and TurboModules assume that it requires main queue setup.

## Script
```
const exec = require("../lib/exec");
const abspath = require("../lib/abspath");
const relpath = require("../lib/relpath");
const readFile = (filename) => require("fs").readFileSync(filename, "utf8");
const writeFile = (filename, content) =>
  require("fs").writeFileSync(filename, content);

function main() {
  const tmFiles = exec("cd ~/fbsource && xbgs -n 10000 -l constantsToExport")
    .split("\n")
    .filter(Boolean);

  const filesWithoutConstantsToExport = [];
  const filesWithConstantsToExportButNotGetConstants = [];
  const filesExplicitlyNotRequiringMainQueueSetup = [];

  tmFiles
    .filter((filename) => {
      if (filename.includes("microsoft-fork-of-react-native")) {
        return false;
      }

      return /\.mm?$/.test(filename);
    })
    .map(abspath)
    .forEach((filename) => {
      const code = readFile(filename);
      const relFilename = relpath(filename);

      if (!/constantsToExport\s*{/.test(code)) {
        filesWithoutConstantsToExport.push(relFilename);
        return;
      }

      if (!/getConstants\s*{/.test(code)) {
        filesWithConstantsToExportButNotGetConstants.push(relFilename);
        return;
      }

      if (/requiresMainQueueSetup\s*{/.test(code)) {
        const requiresMainQueueSetupRegex = /requiresMainQueueSetup\s*{\s*return\s+(?<requiresMainQueueSetup>YES|NO)/;
        const requiresMainQueueSetupRegexMatch = requiresMainQueueSetupRegex.exec(
          code
        );

        if (!requiresMainQueueSetupRegexMatch) {
          throw new Error(
            "Detected requiresMainQueueSetup method in file " +
              relFilename +
              " but was unable to parse the method return value"
          );
        }

        const {
          requiresMainQueueSetup,
        } = requiresMainQueueSetupRegexMatch.groups;

        if (requiresMainQueueSetup == "NO") {
          filesExplicitlyNotRequiringMainQueueSetup.push(relFilename);
          return;
        }
      }

      const getConstantsTypeRegex = () => /-\s*\((?<type>.*)\)getConstants\s*{/;
      const getConstantsTypeRegexMatch = getConstantsTypeRegex().exec(code);

      if (!getConstantsTypeRegexMatch) {
        throw new Error(
          `Failed to parse return type of getConstants method in file ${relFilename}`
        );
      }

      const getConstantsType = getConstantsTypeRegexMatch.groups.type;

      const getConstantsBody = code
        .split(getConstantsTypeRegex())[2]
        .split("\n}")[0];

      const newGetConstantsBody = `
  __block ${getConstantsType} constants;
  RCTUnsafeExecuteOnMainQueueSync(^{${getConstantsBody
    .replace(/\n/g, "\n  ")
    .replace(/_bridge/g, "self->_bridge")
    .replace(/return /g, "constants = ")}
  });

  return constants;
`;

      writeFile(
        filename,
        code
          .replace(getConstantsBody, newGetConstantsBody)
          .replace("#import", "#import <React/RCTUtils.h>\n#import")
      );
    });

  console.log("Files without constantsToExport: ");
  filesWithoutConstantsToExport.forEach((file) => console.log(file));
  console.log();

  console.log("Files with constantsToExport but no getConstants: ");
  filesWithConstantsToExportButNotGetConstants.forEach((file) =>
    console.log(file)
  );
  console.log();

  console.log("Files with requiresMainQueueSetup = NO: ");
  filesExplicitlyNotRequiringMainQueueSetup.forEach((file) =>
    console.log(file)
  );
}

if (!module.parent) {
  main();
}

```

Changelog: [Internal]

Reviewed By: fkgozali

Differential Revision: D21797048

fbshipit-source-id: a822a858fecdbe976e6197f8339e509dc7cd917f

Author: RSNara

React/CoreModules/RCTAppState.mm

@@ -56,9 +56,14 @@ - (dispatch_queue_t)methodQueue
 
 - (facebook::react::ModuleConstants<JS::NativeAppState::Constants>)getConstants
 {
-  return facebook::react::typedConstants<JS::NativeAppState::Constants>({
-      .initialAppState = RCTCurrentAppState(),
+  __block facebook::react::ModuleConstants<JS::NativeAppState::Constants> constants;
+  RCTUnsafeExecuteOnMainQueueSync(^{
+    constants = facebook::react::typedConstants<JS::NativeAppState::Constants>({
+        .initialAppState = RCTCurrentAppState(),
+    });
   });
+
+  return constants;
 }
 
 #pragma mark - Lifecycle

React/CoreModules/RCTDeviceInfo.mm

@@ -122,14 +122,19 @@ static BOOL RCTIsIPhoneX()
 
 - (NSDictionary<NSString *, id> *)getConstants
 {
-  return @{
-    @"Dimensions" : RCTExportedDimensions(_bridge),
-    // Note:
-    // This prop is deprecated and will be removed in a future release.
-    // Please use this only for a quick and temporary solution.
-    // Use <SafeAreaView> instead.
-    @"isIPhoneX_deprecated" : @(RCTIsIPhoneX()),
-  };
+  __block NSDictionary<NSString *, id> *constants;
+  RCTUnsafeExecuteOnMainQueueSync(^{
+    constants = @{
+      @"Dimensions" : RCTExportedDimensions(self->_bridge),
+      // Note:
+      // This prop is deprecated and will be removed in a future release.
+      // Please use this only for a quick and temporary solution.
+      // Use <SafeAreaView> instead.
+      @"isIPhoneX_deprecated" : @(RCTIsIPhoneX()),
+    };
+  });
+
+  return constants;
 }
 
 - (void)didReceiveNewContentSizeMultiplier

React/CoreModules/RCTPlatform.mm

@@ -58,22 +58,27 @@ - (dispatch_queue_t)methodQueue
 
 - (ModuleConstants<JS::NativePlatformConstantsIOS::Constants>)getConstants
 {
-  UIDevice *device = [UIDevice currentDevice];
-  auto versions = RCTGetReactNativeVersion();
-  return typedConstants<JS::NativePlatformConstantsIOS::Constants>({
-      .forceTouchAvailable = RCTForceTouchAvailable() ? true : false,
-      .osVersion = [device systemVersion],
-      .systemName = [device systemName],
-      .interfaceIdiom = interfaceIdiom([device userInterfaceIdiom]),
-      .isTesting = RCTRunningInTestEnvironment() ? true : false,
-      .reactNativeVersion = JS::NativePlatformConstantsIOS::ConstantsReactNativeVersion::Builder(
-          {.minor = [versions[@"minor"] doubleValue],
-           .major = [versions[@"major"] doubleValue],
-           .patch = [versions[@"patch"] doubleValue],
-           .prerelease = [versions[@"prerelease"] isKindOfClass:[NSNull class]]
-               ? folly::Optional<double>{}
-               : [versions[@"prerelease"] doubleValue]}),
+  __block ModuleConstants<JS::NativePlatformConstantsIOS::Constants> constants;
+  RCTUnsafeExecuteOnMainQueueSync(^{
+    UIDevice *device = [UIDevice currentDevice];
+    auto versions = RCTGetReactNativeVersion();
+    constants = typedConstants<JS::NativePlatformConstantsIOS::Constants>({
+        .forceTouchAvailable = RCTForceTouchAvailable() ? true : false,
+        .osVersion = [device systemVersion],
+        .systemName = [device systemName],
+        .interfaceIdiom = interfaceIdiom([device userInterfaceIdiom]),
+        .isTesting = RCTRunningInTestEnvironment() ? true : false,
+        .reactNativeVersion = JS::NativePlatformConstantsIOS::ConstantsReactNativeVersion::Builder(
+            {.minor = [versions[@"minor"] doubleValue],
+             .major = [versions[@"major"] doubleValue],
+             .patch = [versions[@"patch"] doubleValue],
+             .prerelease = [versions[@"prerelease"] isKindOfClass:[NSNull class]]
+                 ? folly::Optional<double>{}
+                 : [versions[@"prerelease"] doubleValue]}),
+    });
   });
+
+  return constants;
 }
 
 - (std::shared_ptr<TurboModule>)getTurboModule:(const ObjCTurboModule::InitParams &)params

React/CoreModules/RCTStatusBarManager.mm

@@ -185,10 +185,15 @@ - (void)applicationWillChangeStatusBarFrame:(NSNotification *)notification
 
 - (facebook::react::ModuleConstants<JS::NativeStatusBarManagerIOS::Constants>)getConstants
 {
-  return facebook::react::typedConstants<JS::NativeStatusBarManagerIOS::Constants>({
-      .HEIGHT = RCTSharedApplication().statusBarFrame.size.height,
-      .DEFAULT_BACKGROUND_COLOR = folly::none,
+  __block facebook::react::ModuleConstants<JS::NativeStatusBarManagerIOS::Constants> constants;
+  RCTUnsafeExecuteOnMainQueueSync(^{
+    constants = facebook::react::typedConstants<JS::NativeStatusBarManagerIOS::Constants>({
+        .HEIGHT = RCTSharedApplication().statusBarFrame.size.height,
+        .DEFAULT_BACKGROUND_COLOR = folly::none,
+    });
   });
+
+  return constants;
 }
 
 - (facebook::react::ModuleConstants<JS::NativeStatusBarManagerIOS::Constants>)constantsToExport

ReactCommon/turbomodule/samples/platform/ios/RCTSampleTurboModule.mm

@@ -7,6 +7,7 @@
 
 #import "RCTSampleTurboModule.h"
 
+#import <React/RCTUtils.h>
 #import <UIKit/UIKit.h>
 
 using namespace facebook::react;
@@ -45,14 +46,19 @@ - (void)invalidate
 
 - (NSDictionary *)getConstants
 {
-  UIScreen *mainScreen = UIScreen.mainScreen;
-  CGSize screenSize = mainScreen.bounds.size;
+  __block NSDictionary *constants;
+  RCTUnsafeExecuteOnMainQueueSync(^{
+    UIScreen *mainScreen = UIScreen.mainScreen;
+    CGSize screenSize = mainScreen.bounds.size;
 
-  return @{
-    @"const1" : @YES,
-    @"const2" : @(screenSize.width),
-    @"const3" : @"something",
-  };
+    constants = @{
+      @"const1" : @YES,
+      @"const2" : @(screenSize.width),
+      @"const3" : @"something",
+    };
+  });
+
+  return constants;
 }
 
 // TODO: Remove once fully migrated to TurboModule.