feat: Return extended app launch span from extendAppLaunch()

[itaybre]

Summary

• SentrySDK.extendAppLaunch() now returns the extended app launch Span?, allowing users to add child spans for granular breakdown of the app start period
• The return value is @discardableResult so this is not a breaking change
• finishExtendedAppLaunch() is preserved for backward compatibility
• Tracer creation is extracted into StandaloneTransactionStrategy.createTracer() to avoid duplication
• Fixed a race condition: the tracer now waits for both the app start measurement (from report()) and the user finishing the span before completing the transaction

Example usage

let appStartSpan = SentrySDK.extendAppLaunch()

let configSpan = appStartSpan?.startChild(operation: "app.init", description: "fetch remote config")
fetchRemoteConfig()
configSpan?.finish()

appStartSpan?.finish()

Test plan

• Existing extended app launch tests pass (updated for new API)
• New tests for returned span, child span creation, and child span inclusion in transaction
• Race condition tests: span finished before measurement arrives (both via span.finish() and finishExtendedAppLaunch())
• AppStartReportingStrategy tests pass
• Sample app updated with child span example
• sdk_api.json regenerated

[github-actions]

	Messages
📖	Do not forget to update Sentry-docs with your feature once the pull request gets approved.

Generated by 🚫 dangerJS against 96507be

[sentry]

📲 Install Builds

iOS

🔗 App Name	App ID	Version	Configuration
SDK-Size	io.sentry.sample.SDK-Size	9.16.0 (1)	Release

⚙️ sentry-cocoa Build Distribution Settings

[codecov]

Codecov Report

❌ Patch coverage is 93.75000% with 5 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (main@2446b3d). Learn more about missing BASE report.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
...StartTracking/SentryExtendedAppLaunchManager.swift	93.333%	4 Missing ⚠️
Sources/Swift/Helper/SentrySDK.swift	0.000%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##             main     #7985   +/-   ##
========================================
  Coverage        ?   86.570%           
========================================
  Files           ?       550           
  Lines           ?     31692           
  Branches        ?     13029           
========================================
  Hits            ?     27436           
  Misses          ?      4207           
  Partials        ?        49           

Files with missing lines	Coverage Δ
Sources/Sentry/SentryAppStartMeasurementProvider.m	100.000% <ø> (ø)
...s/AppStartTracking/AppStartReportingStrategy.swift	100.000% <100.000%> (ø)
...tions/AppStartTracking/SentryAppStartTracker.swift	94.382% <ø> (ø)
Sources/Swift/Helper/SentrySDK.swift	93.650% <0.000%> (ø)
...StartTracking/SentryExtendedAppLaunchManager.swift	95.238% <93.333%> (ø)

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[github-actions]

Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	1223.71 ms	1257.80 ms	34.09 ms
Size	24.14 KiB	1.17 MiB	1.15 MiB

Baseline results on branch: main

Startup times

Revision	Plain	With Sentry	Diff
ba824fc	1212.75 ms	1244.29 ms	31.54 ms
48fa69f	1221.60 ms	1251.52 ms	29.92 ms
e3070ad	1201.60 ms	1235.70 ms	34.10 ms
9da166b	1222.40 ms	1250.24 ms	27.84 ms
6b08499	1231.61 ms	1241.90 ms	10.29 ms
1770336	1225.09 ms	1251.32 ms	26.23 ms
9c19a06	1217.77 ms	1248.98 ms	31.21 ms
bc68ff6	1227.02 ms	1254.89 ms	27.87 ms
a7c42d9	1217.25 ms	1253.98 ms	36.73 ms
8180609	1214.67 ms	1243.36 ms	28.69 ms

App size

Revision	Plain	With Sentry	Diff
ba824fc	24.14 KiB	1.17 MiB	1.15 MiB
48fa69f	24.14 KiB	1.15 MiB	1.13 MiB
e3070ad	24.14 KiB	1.16 MiB	1.14 MiB
9da166b	24.14 KiB	1.16 MiB	1.14 MiB
6b08499	24.14 KiB	1.15 MiB	1.13 MiB
1770336	24.14 KiB	1.15 MiB	1.13 MiB
9c19a06	24.14 KiB	1.16 MiB	1.13 MiB
bc68ff6	24.14 KiB	1.16 MiB	1.14 MiB
a7c42d9	24.14 KiB	1.15 MiB	1.13 MiB
8180609	24.14 KiB	1.16 MiB	1.13 MiB

Previous results on branch: itay/standalone_span

Startup times

Revision	Plain	With Sentry	Diff
c4d5fa5	1223.50 ms	1265.39 ms	41.89 ms
c7ce3b0	1236.80 ms	1269.20 ms	32.40 ms

App size

Revision	Plain	With Sentry	Diff
c4d5fa5	24.14 KiB	1.17 MiB	1.15 MiB
c7ce3b0	24.14 KiB	1.17 MiB	1.15 MiB

[philprime]

Approved but please consider implementing the feedback

[cursor]

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