Repository navigation
[iOS] React Native's headers fail a Swift import built with SWIFT_TREAT_WARNINGS_AS_ERRORS (nullability and deprecation warnings) #59730
Description
Description
An app or a library whose Swift target sets SWIFT_TREAT_WARNINGS_AS_ERRORS = YES cannot import React Native's modules: Xcode precompiles the imported Clang module with the target's warnings as errors, and React Native's own public headers warn there. This happens on main, with both the default prebuilt core and a source build.
#59240 fixed the same kind of warning in RCTHTTPRequestHandler.h and RCTMultipartDataTask.h. These headers still warn on main (f1f1474; the nightly I ran is e57dcb3, four commits behind, and its copies of these headers match main):
React/CoreModules/RCTWebSocketModule.h:23:typedef SRWebSocket * (^SRWebSocketProvider)(NSURLRequest *request);is insideNS_ASSUME_NONNULL, but the block typedef's pointers are not inferred, so-Wnullability-completenessfires.React/Fabric/Utils/RCTReactTaggedView.h:29:- (BOOL)isEqual:(id)other;insideNS_ASSUME_NONNULLmakes the parameternonnull, which conflicts with NSObject'snullable id.React/CoreModules/RCTRedBox+Internal.h,RCTRedBox2Controller+Internal.handRCTRedBox2ErrorParser+Internal.h: each hasnullablemembers and noNS_ASSUME_NONNULLregion, so every other pointer warns.Libraries/AppDelegate/RCTUIConfiguratorProtocol.h:40:- (void)customizeRootView:(RCTRootView *)rootView;uses the deprecatedRCTRootView, so-Wdeprecated-declarationsfires in the module build.
The source build stops at the first module that fails (React_RCTAppDelegate), so it does not reach RCTWebSocketModule.h, which the prebuilt run shows.
Steps to reproduce
The reproducer is the reproducer template with react-native@0.89.0-nightly-20261031-e57dcb3cc (built from main), @react-native-community/cli@21.0.0-alpha.1 (the nightly needs it for autolinking), and SWIFT_TREAT_WARNINGS_AS_ERRORS = YES on the app target. The template's SceneDelegate.swift already has import React and import React_RCTAppDelegate. No simulator or signing is needed.
cd ReproducerApp && npm installcd ios && pod installxcodebuild -workspace ReproducerApp.xcworkspace -scheme ReproducerApp -configuration Debug -sdk iphonesimulator -destination 'generic/platform=iOS Simulator' CODE_SIGNING_ALLOWED=NO build- Then
RCT_USE_PREBUILT_RNCORE=0 pod installand the samexcodebuildcommand, to build React Native from source.
Expected: the app builds, since nothing in it warns.
Seen: ** BUILD FAILED ** in SwiftExplicitDependencyGeneratePcm, on warnings in React Native's headers (see the logs below).
React Native Version
0.89.0-nightly-20261031-e57dcb3cc
Affected Platforms
Runtime - iOS, Build - MacOS
Output of npx @react-native-community/cli info
System:
OS: macOS 27.0.1
CPU: (8) arm64 Apple M1
Memory: 500.36 MB / 8.00 GB
Shell:
version: "5.9"
path: /bin/zsh
Binaries:
Node:
version: 26.12.1
path: /Users/yevhenii/.nvm/versions/node/v26.12.1/bin/node
Yarn: Not Found
npm:
version: 12.2.1
path: /Users/yevhenii/.nvm/versions/node/v26.12.1/bin/npm
Watchman:
version: 2026.10.19.00
path: /opt/homebrew/bin/watchman
Managers:
CocoaPods:
version: 1.17.0
path: /opt/homebrew/bin/pod
SDKs:
iOS SDK:
Platforms:
- DriverKit 27.2
- iOS 27.2
- macOS 27.2
- tvOS 27.2
- visionOS 27.2
- watchOS 27.2
Android SDK: Not Found
IDEs:
Android Studio: Not Found
Xcode:
version: 27.2/27B52
path: /usr/bin/xcodebuild
Languages:
Java: Not Found
Ruby:
version: 4.0.9
path: /opt/homebrew/bin/ruby
npmPackages:
"@react-native-community/cli":
installed: 21.0.0-alpha.1
wanted: 21.0.0-alpha.1
react:
installed: 19.3.0
wanted: 19.3.0
react-native:
installed: 0.89.0-nightly-20261031-e57dcb3cc
wanted: 0.89.0-nightly-20261031-e57dcb3cc
react-native-macos: Not Found
npmGlobalPackages:
"*react-native*": Not Found
Android:
hermesEnabled: true
newArchEnabled: true
iOS:
hermesEnabled: Not found
newArchEnabled: false
Stacktrace or Logs
# step 3, default prebuilt core (paths below the temporary folder shortened to …/)
…/derived-data/Build/Products/Debug-iphonesimulator/XCFrameworkIntermediates/React-Core-prebuilt/React.framework/Headers/RCTReactTaggedView.h:29:21: error: conflicting nullability specifier on parameter types, 'nonnull' conflicts with existing specifier 'nullable'
…/derived-data/Build/Products/Debug-iphonesimulator/XCFrameworkIntermediates/React-Core-prebuilt/React.framework/Headers/RCTWebSocketModule.h:23:21: error: pointer is missing a nullability type specifier (_Nonnull, _Nullable, or _Null_unspecified)
<unknown>:0: error: failed to emit precompiled module '…/derived-data/Build/Intermediates.noindex/SwiftExplicitPrecompiledModules/React-EB9M1Z4OHNICYJK47EJBN2CQ0.pcm' for module map '…/derived-data/Build/Products/Debug-iphonesimulator/XCFrameworkIntermediates/React-Core-prebuilt/React.framework/Modules/module.modulemap'
** BUILD FAILED **
The following build commands failed:
SwiftExplicitDependencyGeneratePcm arm64 …/derived-data/Build/Intermediates.noindex/SwiftExplicitPrecompiledModules/React-EB9M1Z4OHNICYJK47EJBN2CQ0.pcm
# step 4, RCT_USE_PREBUILT_RNCORE=0
…/ReproducerApp/ios/Pods/Headers/Public/React-Core/React/RCTRedBox+Internal.h:17:44: error: pointer is missing a nullability type specifier (_Nonnull, _Nullable, or _Null_unspecified)
…/ReproducerApp/ios/Pods/Headers/Public/React-Core/React/RCTRedBox2Controller+Internal.h:20:4: error: pointer is missing a nullability type specifier (_Nonnull, _Nullable, or _Null_unspecified)
…/ReproducerApp/ios/Pods/Headers/Public/React-Core/React/RCTRedBox2ErrorParser+Internal.h:17:38: error: pointer is missing a nullability type specifier (_Nonnull, _Nullable, or _Null_unspecified)
…/ReproducerApp/ios/Pods/Headers/Public/React-Core/React/RCTRedBox2ErrorParser+Internal.h:41:24: error: pointer is missing a nullability type specifier (_Nonnull, _Nullable, or _Null_unspecified)
…/ReproducerApp/ios/Pods/Headers/Public/React-Core/React/RCTRedBox2ErrorParser+Internal.h:41:54: error: pointer is missing a nullability type specifier (_Nonnull, _Nullable, or _Null_unspecified)
…/ReproducerApp/ios/Pods/Headers/Public/React-RCTAppDelegate/RCTUIConfiguratorProtocol.h:40:28: error: 'RCTRootView' is deprecated: This API will be removed along with the legacy architecture.
<unknown>:0: error: failed to emit precompiled module '…/derived-data/Build/Intermediates.noindex/SwiftExplicitPrecompiledModules/React_RCTAppDelegate-B8C35ZXJIXKD5SNK3CAGCPF8S.pcm' for module map '…/ReproducerApp/ios/Pods/Headers/Public/React_RCTAppDelegate/React-RCTAppDelegate.modulemap'
** BUILD FAILED **
The following build commands failed:
SwiftExplicitDependencyGeneratePcm x86_64 …/derived-data/Build/Intermediates.noindex/SwiftExplicitPrecompiledModules/React_RCTAppDelegate-B8C35ZXJIXKD5SNK3CAGCPF8S.pcm
macOS 27.0.1, Xcode 27.2 (27B52), Apple Swift 6.4.2, CocoaPods 1.17.0, Node 26.12.1, npm 12.2.1.
#57524 reported the RCTWebSocketModule.h warning under the prebuilt path in 0.86.0 and was closed without a reproducer.
MANDATORY Reproducer
https://github.com/YevheniiKotyrlo/react-native-react-core-headers-warnings-as-errors
Screenshots and Videos
No response
Activity
dave-otf commentedon Nov 1, 2026
Since the repro already covers both prebuilt and source builds, a small CI smoke job for each
pod installmode using the same warnings-as-errorsxcodebuildflags could keep this from regressing. Keeping the nullability and deprecation cases identifiable in the failure output would also make future header fixes easier to verify.