fix: Make Scope.span fully thread safe

[philipphofmann]

📜 Description

Setting the span on the scope and useSpan were thread safe, but not setSpan. This is fixed now.

💡 Motivation and Context

This came up while investigating #4513.

💚 How did you test it?

Unit tests.

📝 Checklist

You have to check all boxes before merging:

• I reviewed the submitted code.
• I added tests to verify the changes.
• No new PII added or SDK only sends newly added PII if sendDefaultPII is enabled.
• I updated the docs if needed.
• Review from the native team if needed.
• No breaking change or entry added to the changelog.
• No breaking change for hybrid SDKs or communicated to hybrid SDKs.

🔮 Next steps

[github-actions]

Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	1232.70 ms	1235.96 ms	3.25 ms
Size	22.30 KiB	730.03 KiB	707.73 KiB

Baseline results on branch: main

Startup times

Revision	Plain	With Sentry	Diff
6bc5ae5	1207.23 ms	1216.66 ms	9.43 ms
65e48e0	1223.68 ms	1238.96 ms	15.28 ms
5616e0a	1224.12 ms	1249.86 ms	25.74 ms
6943de0	1230.02 ms	1235.32 ms	5.30 ms
3db3e35	1233.52 ms	1256.43 ms	22.90 ms
aea5987	1223.84 ms	1244.39 ms	20.55 ms
ed49f0c	1245.67 ms	1261.15 ms	15.48 ms
20a828b	1211.33 ms	1228.00 ms	16.67 ms
af1f4dd	1225.39 ms	1245.48 ms	20.09 ms
50bb751	1234.10 ms	1248.29 ms	14.19 ms

App size

Revision	Plain	With Sentry	Diff
6bc5ae5	20.76 KiB	401.39 KiB	380.63 KiB
65e48e0	21.90 KiB	708.34 KiB	686.44 KiB
5616e0a	22.85 KiB	407.44 KiB	384.59 KiB
6943de0	20.76 KiB	393.33 KiB	372.57 KiB
3db3e35	21.58 KiB	419.21 KiB	397.63 KiB
aea5987	21.58 KiB	418.13 KiB	396.54 KiB
ed49f0c	21.58 KiB	632.13 KiB	610.55 KiB
20a828b	21.58 KiB	670.99 KiB	649.41 KiB
af1f4dd	22.85 KiB	414.71 KiB	391.86 KiB
50bb751	21.58 KiB	417.86 KiB	396.27 KiB

Previous results on branch: fix/scope-get-span-lock

Startup times

Revision	Plain	With Sentry	Diff
582e4c8	1209.23 ms	1222.73 ms	13.51 ms

App size

Revision	Plain	With Sentry	Diff
582e4c8	21.90 KiB	727.73 KiB	705.82 KiB

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.535%. Comparing base (4509e9c) to head (0da7052).
Report is 4 commits behind head on main.

Additional details and impacted files

@@              Coverage Diff              @@
##              main     #4519       +/-   ##
=============================================
+ Coverage   91.513%   91.535%   +0.022%     
=============================================
  Files          615       615               
  Lines        69460     69489       +29     
  Branches     24896     24921       +25     
=============================================
+ Hits         63565     63607       +42     
+ Misses        5802      5789       -13     
  Partials        93        93               

Files with missing lines	Coverage Δ
Sources/Sentry/SentryScope.m	96.859% <100.000%> (+0.015%)	⬆️
Tests/SentryTests/SentryScopeSwiftTests.swift	99.056% <100.000%> (+0.024%)	⬆️

... and 6 files with indirect coverage changes

---

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[brustolin]

LGTM

[brustolin]

Also I dont think we need useSpan anymore, we should mark it as deprecated.

[philipphofmann]

Also I dont think we need useSpan anymore, we should mark it as deprecated.

We still use useSpan in multiple places in the SDK. We can consider removing it in the next version.