[iOS] Session Replay fails to build with Xcode 27: Unknown type name 'RCTPromiseResolveBlock' in generated -Swift.h header

[benupstart]

Describe the bug

The @datadog/mobile-react-native-session-replay fails to compile under Xcode 27 beta (Swift 6.4):

In file included from node_modules/@datadog/mobile-react-native-session-replay/ios/Sources/DdSessionReplay.mm:8:
DerivedSources/DatadogSDKReactNativeSessionReplay-Swift.h:788:415: error: unknown type name 'RCTPromiseResolveBlock'
DerivedSources/DatadogSDKReactNativeSessionReplay-Swift.h:788:478: error: unknown type name 'RCTPromiseRejectBlock'
DerivedSources/DatadogSDKReactNativeSessionReplay-Swift.h:789:51:  error: unknown type name 'RCTPromiseResolveBlock'
DerivedSources/DatadogSDKReactNativeSessionReplay-Swift.h:789:114: error: unknown type name 'RCTPromiseRejectBlock'
DerivedSources/DatadogSDKReactNativeSessionReplay-Swift.h:790:50:  error: unknown type name 'RCTPromiseResolveBlock'
DerivedSources/DatadogSDKReactNativeSessionReplay-Swift.h:790:113: error: unknown type name 'RCTPromiseRejectBlock'
6 errors generated.

Why it happens

The pod's Swift code exposes three methods to Objective-C (enable, startRecording, stopRecording), and their signatures use React Native's promise-callback types, RCTPromiseResolveBlock and RCTPromiseRejectBlock. When Xcode builds the pod, it auto-generates an Objective-C header (DatadogSDKReactNativeSessionReplay-Swift.h) from those Swift methods — and that generated header mentions the two React typedefs without ever importing the React header that defines them (React/RCTBridgeModule.h).

It has technically always been broken, but Xcode 26 and earlier papered over it: the compiler would implicitly resolve the missing types through its module system. Xcode 27's Swift 6.4 toolchain stopped doing that, so the typedefs are now genuinely undefined where they're used, and compilation fails.

Our fix

We patch the package locally (Yarn patch). The core change: in the Swift file, replace the two React typealiases with their exact structural equivalents, (Any?) -> Void for resolve and (String?, String?, Error?) -> Void for reject. These are the same underlying types, so nothing changes at runtime; but the generated header no longer references any React names, so it compiles regardless of import order. Two defensive React imports were also added on the Objective-C side.

Reproduction steps

1. RN app with @datadog/mobile-react-native-session-replay (any version incl. 3.6.0), New Architecture enabled, static libraries (no use_frameworks!)
2. Build with Xcode 27
3. Compilation of the session-replay pod fails with the error above

SDK logs

No response

Expected behavior

Suggested fix, we expect the build to complete and not fail:

Replace the RCT typealiases in the @objc method signatures with their structural equivalents, so the generated header emits raw block types with no React dependency:

// Before
public func startRecording(resolve: RCTPromiseResolveBlock, reject: RCTPromiseRejectBlock) -> Void {

// After
public func startRecording(resolve: (Any?) -> Void, reject: (String?, String?, Error?) -> Void) -> Void {

Affected SDK versions

3.6.0

Latest working SDK version

NA (not working on any version)

Did you confirm if the latest SDK version fixes the bug?

Yes

Integration Methods

NPM

React Native Version

0.85.2

Package.json Contents

No response

iOS Setup

No response

Android Setup

No response

Device Information

No response

Other relevant information

No response

[benupstart]

Here is the patch we are using locally to fix the build errors:

diff --git a/ios/Sources/DdPrivacyViewFabric.h b/ios/Sources/DdPrivacyViewFabric.h
index 2806cad49d5f281458ed36ba7b9b8feede241793..971ecd59a0c5cb822124d07955159cdaa975e97a 100644
--- a/ios/Sources/DdPrivacyViewFabric.h
+++ b/ios/Sources/DdPrivacyViewFabric.h
@@ -14,6 +14,9 @@
 #import <react/renderer/components/DdSDKReactNativeSessionReplay/RCTComponentViewHelpers.h>
 #import <React/RCTFabricComponentsPlugins.h>
 
+// Defensive: make the RCT block typedefs visible before the generated
+// -Swift.h header (Xcode 27 / Swift 6.4 no longer resolves them implicitly).
+#import <React/RCTBridgeModule.h>
 
 #if __has_include("DatadogSDKReactNativeSessionReplay-Swift.h")
 #import <DatadogSDKReactNativeSessionReplay-Swift.h>
diff --git a/ios/Sources/DdSessionReplay.mm b/ios/Sources/DdSessionReplay.mm
index 942c374508814a9168a9735e65f748600a1132eb..4d8dc095c03cdd709eb33279ed4deb1a3772cbe5 100644
--- a/ios/Sources/DdSessionReplay.mm
+++ b/ios/Sources/DdSessionReplay.mm
@@ -3,6 +3,9 @@
  * This product includes software developed at Datadog (https://www.datadoghq.com/).
  * Copyright 2016-Present Datadog, Inc.
  */
+// Defensive: make the RCT block typedefs visible before the generated
+// -Swift.h header (Xcode 27 / Swift 6.4 no longer resolves them implicitly).
+#import <React/RCTBridgeModule.h>
 // Import this first to prevent require cycles
 #if __has_include("DatadogSDKReactNativeSessionReplay-Swift.h")
 #import <DatadogSDKReactNativeSessionReplay-Swift.h>
diff --git a/ios/Sources/DdSessionReplayImplementation.swift b/ios/Sources/DdSessionReplayImplementation.swift
index 0fc9c6637ab64ea749f569432f63bbad63f85887..5a714e669f30784367eb20f87211ebd2ec6befb0 100644
--- a/ios/Sources/DdSessionReplayImplementation.swift
+++ b/ios/Sources/DdSessionReplayImplementation.swift
@@ -50,8 +50,12 @@ public class DdSessionReplayImplementation: NSObject {
         touchPrivacyLevel: NSString,
         textAndInputPrivacyLevel: NSString,
         startRecordingImmediately: Bool,
-        resolve:RCTPromiseResolveBlock,
-        reject:RCTPromiseRejectBlock
+        // Structural closure types (matching RCTPromiseResolveBlock /
+        // RCTPromiseRejectBlock) so the generated -Swift.h header does not
+        // reference React typedefs it never imports — Xcode 27 (Swift 6.4)
+        // errors on them when compiling the header in a module context.
+        resolve: (Any?) -> Void,
+        reject: (String?, String?, Error?) -> Void
     ) -> Void {
         var customEndpointURL: URL? = nil
         if (customEndpoint != "") {
@@ -98,13 +102,13 @@ public class DdSessionReplayImplementation: NSObject {
     }
     
     @objc
-    public func startRecording(resolve: RCTPromiseResolveBlock, reject: RCTPromiseRejectBlock) -> Void {
+    public func startRecording(resolve: (Any?) -> Void, reject: (String?, String?, Error?) -> Void) -> Void {
         sessionReplay.startRecording(in: CoreRegistry.default)
         resolve(nil)
     }
     
     @objc
-    public func stopRecording(resolve: RCTPromiseResolveBlock, reject: RCTPromiseRejectBlock) -> Void {
+    public func stopRecording(resolve: (Any?) -> Void, reject: (String?, String?, Error?) -> Void) -> Void {
         sessionReplay.stopRecording(in: CoreRegistry.default)
         resolve(nil)
     }