feat(flags): send the split serial ID on iOS exposure events (EX-3422) by danyal002 · Pull Request #1410 · DataDog/dd-sdk-reactnative

danyal002 · 2026-09-09T19:11:05Z

What does this PR do?

The iOS bridge now sends the split serial ID on feature flag exposure events.

File	Change
`packages/core/DatadogSDKReactNative.podspec` and 2 other podspecs	Moves the iOS SDK to `3.17.0`.
`example/ios/Podfile.lock`, `example-new-architecture/ios/Podfile.lock`, `benchmarks/ios/Podfile.lock`	Locks the iOS SDK pods at `3.17.0`.
`packages/core/ios/Sources/DdFlagsImplementation.swift`	Reads and writes `serialId` in both bridge directions. Maps the new `initializationTimedOut` error.
`packages/core/ios/Tests/DdFlagsTests.swift`	Adds 7 tests.
`packages/core/ios/Tests/MockDatadogCore.swift` and 3 other test mocks	Implement `remoteConfiguration`.
`packages/internal-testing-tools/ios/Sources/DatadogCoreProxy.swift`	Forwards `remoteConfiguration` to the wrapped core.
`packages/core/ios/Tests/DdTraceTests.swift`	Fixes a race in `testTracingConcurrently`.

iOS SDK 3.17.0 adds serialID to FlagAssignment, reads it on the exposure event, and includes it in the exposure deduplication cache. The React Native bridge supplies the value.

The bridge converts a FlagAssignment to an NSDictionary with a fixed key list, and converts the dictionary back for exposure tracking. The key list omitted the serial ID. The value was therefore dropped in both directions, and the code still compiled.

The serial ID crosses the bridge as a string. Android does the same, because React Native converts integers to Double. An assignment with no serial ID omits the key instead of sending NSNull.

The reader accepts a string only. NSNumber and Bool bridge into each other on Apple platforms, so a numeric branch would read a boolean true as serial ID 1. Int(String) rejects a boolean, and rejects any other value that is not an integer. A malformed serial ID yields no serial ID. It never rejects the assignment, because that would drop the exposure event for the whole flag.

Serial IDs are zero-based for each org. 0 is therefore a real value, and three tests pin it.

iOS SDK 3.17.0 also changes two APIs that the bridge and its tests depend on. FlagsError adds initializationTimedOut, and the bridge rejects it with the error code INITIALIZATION_TIMED_OUT. DatadogCoreProtocol adds remoteConfiguration. The test mocks return nil, as NOPDatadogCore does. DatadogCoreProxy forwards the value from the core that it wraps.

Motivation

The UFC compiler rewrites a holdout into an ordinary allocation before any SDK reads the flag configuration. An exposure event therefore records no holdout. The split serial ID is the only link back to it. An exposure event without the serial ID cannot be resolved to a holdout.

Additional Notes

Testing. The new tests cover the string form, serial ID 0 in both directions, an absent serial ID omitting the key, four malformed values, a round trip through both conversions, and the INITIALIZATION_TIMED_OUT error code. The DatadogSDKReactNative and DatadogSDKReactNativeSessionReplay test schemes pass on an iOS simulator.

testTracingConcurrently failed intermittently on develop, for example on PR #1409. Its concurrent iterations shared one variable for the span ID. Another iteration could overwrite the value between startSpan and finishSpan, so one span stayed open. Each iteration now keeps its own span ID. The test passed 100 consecutive runs on a simulator.

Risks. The iOS SDK bump from 3.16.0 to 3.17.0 carries every other change in that release.

The bridge ignores a numeric serial ID, whereas the Android bridge accepts a string or a number. Every JavaScript producer sends a string: the native snapshot, the OpenFeature offline adapter, and the core precomputed decoder. No current caller therefore depends on the numeric shape. A test pins the numeric case as ignored, so the difference is deliberate and visible.

The OpenFeature offline path already sends the serial ID. PR #1409 adds it to the core client's offline path. Android already sends the serial ID.

datadog-datadog-prod-us1-2 · 2026-09-09T19:18:39Z

✅ All CI checks and tests passed.

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🧪 All tests passed
❄️ No new flaky tests detected

_{This comment will be updated automatically if new data arrives.

🔗 Commit SHA: 3cd6690 | Docs | View more details | Give us feedback!}

Bump the iOS SDK to 3.17.0, which adds serialID to FlagAssignment, and send the value through the React Native bridge. The iOS bridge converts FlagAssignment to an NSDictionary with a fixed key list, and converts it back for exposure tracking. The key list omitted the serial ID, so the value was dropped in both directions. The code still compiled, so nothing reported the loss. The serial ID crosses the bridge as a string, for parity with Android, which sends a string because React Native converts integers to Double. An assignment with no serial ID omits the key instead of sending NSNull. The reader accepts a string only. NSNumber and Bool bridge into each other on Apple platforms, so a numeric branch would read a boolean true as serial ID 1. Int(String) rejects that. A malformed serial ID yields no serial ID and never rejects the assignment, because that would drop the exposure event for the whole flag.

Copilot

🟢 Approval recommended

The implementation and coverage are complete, with only a non-blocking wording correction identified.

1 open finding

Correct documentation of malformed input handling · New

What changed in this PR

Adds iOS split serial IDs to feature-flag exposure events.

Changes:

Serializes and restores serialId across the iOS bridge.
Adds coverage for valid, absent, zero, malformed, and round-tripped IDs.
Upgrades Datadog iOS dependencies to 3.17.0.

File	Description
`packages/core/ios/Sources/DdFlagsImplementation.swift`	Bridges serial IDs as strings.
`packages/core/ios/Tests/DdFlagsTests.swift`	Tests serial-ID conversion behavior.
`packages/core/DatadogSDKReactNative.podspec`	Upgrades core iOS SDK pods.
`packages/react-native-webview/DatadogSDKReactNativeWebView.podspec`	Upgrades WebView pods.
`packages/react-native-session-replay/DatadogSDKReactNativeSessionReplay.podspec`	Upgrades Session Replay pod.
`example/ios/Podfile.lock`	Locks upgraded dependencies.
`example-new-architecture/ios/Podfile.lock`	Locks upgraded dependencies.
`benchmarks/ios/Podfile.lock`	Locks upgraded dependencies.

🧠 Review effort: Balanced

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Copilot

🟢 Approval recommended

The bridge implementation, dependency updates, and focused tests consistently cover the intended serial-ID behavior.

0 open findings

1 resolved since last review

Correct documentation of malformed input handling

🧠 Review effort: Balanced

Copilot

🔵 Needs a closer look

The cross-module iOS SDK upgrade needs native build and regression validation before human approval.

0 open findings

🧠 Review effort: Balanced

sameerank

The serial-ID forwarding changes look good! Codex found a couple issues on the SDK 3.17.0 upgrade that might need addressing. Please double check if valid

sameerank · 2026-10-14T18:15:32Z

+  s.dependency 'DatadogTrace', '3.17.0'
+  s.dependency 'DatadogRUM', '3.17.0'
+  s.dependency 'DatadogCrashReporting', '3.17.0'
+  s.dependency 'DatadogFlags', '3.17.0'


[P1] Handle the new initialization timeout error before upgrading DatadogFlags

SDK 3.17.0 adds FlagsError.initializationTimedOut, but the error switch in DdFlagsImplementation.swift still handles only the previous four cases. This makes the switch non-exhaustive and breaks iOS compilation, regardless of whether feature flags are enabled. I reproduced the compiler error against the 3.17.0 enum. Please add a JavaScript error mapping for .initializationTimedOut and a corresponding test alongside this dependency bump.

sameerank · 2026-10-14T18:16:40Z

-  s.dependency 'DatadogRUM', '3.16.0'
-  s.dependency 'DatadogCrashReporting', '3.16.0'
-  s.dependency 'DatadogFlags', '3.16.0'
+  s.dependency 'DatadogCore', '3.17.0'


[P1] Account for the minimum OS version increase in SDK 3.17.0

SDK 3.17.0 raises the minimum supported iOS and tvOS versions from 12.0 to 15.0, while the React Native podspecs still declare 12.0. Applications targeting versions 12–14 will therefore fail CocoaPods dependency resolution after upgrading. The example’s 15.1 deployment target masks this incompatibility. Please preserve the existing minimum through a compatible native SDK release, or explicitly handle and document the platform-support change, including updating the podspec deployment targets.

The DatadogCore 3.17.0 podspec explicitly sets both iOS and tvOS deployment targets to 15.0.

This also applies to the Session Replay and WebView podspecs, which retain the older deployment targets.

Hmm, this is a question for @DataDog/rum-mobile I think. Is it safe to raise the minimum?

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Copilot

🔵 Needs a closer look

No concrete defects were identified, but the SDK-wide upgrade requires human confirmation of native compatibility beyond the reported simulator tests.

0 open findings

🧠 Review effort: Balanced

sbarrio · 2026-10-15T08:26:07Z

Hmm, this is a question for @DataDog/rum-mobile I think. Is it safe to raise the minimum?

Hi @danyal002, I still have to properly review the whole PR, but just be aware that the bump of the iOS SDK to 3.17.0 is blocked at the moment, as it includes breaking changes (it drops support for iOS 12, 13 and 14).

The plan is to do a one-off breaking v3 release in the next few weeks that will include that bump as well as the support for SPM (dropping Cocoapods).

Just so you are aware that this PR won't be able to be merged until that happens so you can plan accordingly.

danyal002 · 2026-10-15T14:27:19Z

Hmm, this is a question for @DataDog/rum-mobile I think. Is it safe to raise the minimum?

Hi @danyal002, I still have to properly review the whole PR, but just be aware that the bump of the iOS SDK to 3.17.0 is blocked at the moment, as it includes breaking changes (it drops support for iOS 12, 13 and 14).

The plan is to do a one-off breaking v3 release in the next few weeks that will include that bump as well as the support for SPM (dropping Cocoapods).

Just so you are aware that this PR won't be able to be merged until that happens so you can plan accordingly.

@sbarrio Thanks! That makes sense. I'll put this PR back in draft and check back in a few weeks.

marco-saia-datadog added the flags label Oct 9, 2026

danyal002 added 2 commits October 14, 2026 13:52

Update Podfile.lock files for iOS SDK 3.17.0

9cf32f3

danyal002 force-pushed the danyal.khan/EX-3422-ios branch from 705ae26 to 9cf32f3 Compare October 14, 2026 17:54

danyal002 marked this pull request as ready for review October 14, 2026 17:54

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Comment thread packages/core/ios/Tests/DdFlagsTests.swift Outdated

Fix the malformed serial ID test comment

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Copilot AI balanced review requested due to automatic review settings October 14, 2026 18:03

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Support iOS SDK 3.17.0 API changes

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sameerank reviewed Oct 14, 2026

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Test the initialization timeout error mapping

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Copilot AI balanced review requested due to automatic review settings October 14, 2026 18:28

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Fix the race in testTracingConcurrently

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maciejburda requested a review from sbarrio October 15, 2026 07:06

danyal002 marked this pull request as draft October 15, 2026 14:27

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feat(flags): send the split serial ID on iOS exposure events (EX-3422) - #1410

feat(flags): send the split serial ID on iOS exposure events (EX-3422)#1410
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