impr: Stop sending empty thread names

[philipphofmann]

📜 Description

Set the thread name to nil when retrieving the thread name from the machine context wrapper in case it fails or the thread name is empty. This slightly reduces the payload size.

💡 Motivation and Context

Came up here #3359 (comment).

💚 How did you test it?

Unit test and running the sample app on a simulator

📝 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

[codecov]

Codecov Report

Merging #3361 (191adbe) into main (2124551) will decrease coverage by 0.032%.
Report is 1 commits behind head on main.
The diff coverage is 100.000%.

@@              Coverage Diff              @@
##              main     #3361       +/-   ##
=============================================
- Coverage   89.251%   89.219%   -0.032%     
=============================================
  Files          500       500               
  Lines        54657     54690       +33     
  Branches     19618     19625        +7     
=============================================
+ Hits         48782     48794       +12     
- Misses        5004      5026       +22     
+ Partials       871       870        -1     

Files	Coverage Δ
...s/Sentry/SentryCrashDefaultMachineContextWrapper.m	100.000% <100.000%> (ø)
Sources/Sentry/SentrySpan.m	95.569% <100.000%> (-0.083%)	⬇️
Sources/Sentry/SentryThreadInspector.m	98.400% <100.000%> (+0.066%)	⬆️
Tests/SentryTests/Protocol/SentryThreadTests.swift	100.000% <100.000%> (ø)
...Tests/SentryCrash/SentryThreadInspectorTests.swift	82.558% <100.000%> (+1.230%)	⬆️

... and 17 files with indirect coverage changes

---

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[github-actions]

Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	1213.80 ms	1239.57 ms	25.78 ms
Size	22.85 KiB	411.66 KiB	388.81 KiB

Baseline results on branch: main

Startup times

Revision	Plain	With Sentry	Diff
f715499	1234.26 ms	1259.40 ms	25.14 ms
66922ca	1221.68 ms	1235.98 ms	14.30 ms
3cba0e8	1236.29 ms	1271.21 ms	34.92 ms
8f397a7	1230.10 ms	1253.88 ms	23.77 ms
2e88e64	1233.64 ms	1241.53 ms	7.89 ms
24b4df1	1240.98 ms	1253.98 ms	13.00 ms
7bb0873	1226.18 ms	1247.30 ms	21.12 ms
2124551	1201.23 ms	1225.34 ms	24.11 ms
25bcc50	1240.47 ms	1254.70 ms	14.23 ms
11ccc16	1203.82 ms	1237.06 ms	33.24 ms

App size

Revision	Plain	With Sentry	Diff
f715499	20.76 KiB	427.23 KiB	406.47 KiB
66922ca	20.76 KiB	425.80 KiB	405.04 KiB
3cba0e8	22.84 KiB	403.19 KiB	380.34 KiB
8f397a7	20.76 KiB	420.55 KiB	399.79 KiB
2e88e64	22.85 KiB	408.88 KiB	386.03 KiB
24b4df1	20.76 KiB	425.77 KiB	405.01 KiB
7bb0873	22.85 KiB	407.09 KiB	384.24 KiB
2124551	22.85 KiB	411.69 KiB	388.84 KiB
25bcc50	20.76 KiB	427.22 KiB	406.46 KiB
11ccc16	20.76 KiB	431.71 KiB	410.95 KiB

Previous results on branch: improvement/emtpy-thread-names

Startup times

Revision	Plain	With Sentry	Diff
1aa71f7	1229.76 ms	1240.24 ms	10.48 ms

App size

Revision	Plain	With Sentry	Diff
1aa71f7	22.85 KiB	411.71 KiB	388.86 KiB

[armcknight]

Code looks fine, but does the server expect something to be in this field? What happens if the field isn't present?

[brustolin]

LGTM, I would just check what @armcknight pointed out, about the server being ok with this.

[philipphofmann]

Great question, @armcknight 👍

thread.name is part of span data. You don't have to send it. You can omit it. This is when you skip it for spans.

And when you send it

For threads on events, you can omit the thread name. It's an optional field see https://develop.sentry.dev/sdk/event-payloads/threads/#attributes.