fix: Crash when initializing SentryHub manually

[philipphofmann]

📜 Description

Fix a crash when serializing the trace context after initializing the SentryHub manually.

💡 Motivation and Context

A user reported a crash on Discord when running the following code

let sentryOption = Options()
sentryOption.dsn = dsn
        
let scope = Scope()
self.sentryHub = SentryHub(client: SentryClient(options: sentryOption), andScope: scope)

let error = NSError(domain: "abc", code: 12)
sentryHub.capture(error: error)

💚 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

[codecov]

Codecov Report

Merging #3374 (598bd45) into main (c471221) will increase coverage by 0.021%.
The diff coverage is 100.000%.

@@              Coverage Diff              @@
##              main     #3374       +/-   ##
=============================================
+ Coverage   89.053%   89.074%   +0.021%     
=============================================
  Files          521       521               
  Lines        56045     56135       +90     
  Branches     20170     20212       +42     
=============================================
+ Hits         49910     50002       +92     
  Misses        5220      5220               
+ Partials       915       913        -2     

Files	Coverage Δ
Sources/Sentry/SentryClient.m	97.588% <100.000%> (+0.008%)	⬆️
Sources/Sentry/SentryNetworkTracker.m	92.571% <100.000%> (+0.085%)	⬆️
Sources/Sentry/SentryPropagationContext.m	100.000% <ø> (ø)
Sources/Sentry/SentryTraceContext.m	92.035% <100.000%> (+0.773%)	⬆️
...erformance/Network/SentryNetworkTrackerTests.swift	97.336% <100.000%> (+0.029%)	⬆️
Tests/SentryTests/SentryClientTests.swift	96.028% <100.000%> (+0.002%)	⬆️
Tests/SentryTests/SentryHubTests.swift	98.381% <100.000%> (+0.015%)	⬆️
...entryTests/Transaction/SentryTraceStateTests.swift	100.000% <100.000%> (ø)

... and 16 files with indirect coverage changes

---

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[github-actions]

Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	1237.76 ms	1244.58 ms	6.82 ms
Size	22.85 KiB	414.11 KiB	391.26 KiB

Baseline results on branch: main

Startup times

Revision	Plain	With Sentry	Diff
279841c	1250.80 ms	1263.08 ms	12.29 ms
c319795	1205.12 ms	1231.20 ms	26.08 ms
89bc37d	1228.20 ms	1257.10 ms	28.90 ms
1437c68	1244.86 ms	1254.18 ms	9.32 ms
5616e0a	1237.00 ms	1260.43 ms	23.43 ms
67460f4	1244.56 ms	1255.96 ms	11.40 ms
3a31fc9	1237.35 ms	1249.02 ms	11.67 ms
01a28a9	1200.78 ms	1227.90 ms	27.12 ms
72c8d84	1238.96 ms	1247.34 ms	8.38 ms
e324230	1225.84 ms	1250.40 ms	24.57 ms

App size

Revision	Plain	With Sentry	Diff
279841c	22.84 KiB	403.19 KiB	380.34 KiB
c319795	20.76 KiB	431.99 KiB	411.22 KiB
89bc37d	20.76 KiB	401.53 KiB	380.77 KiB
1437c68	22.85 KiB	410.96 KiB	388.11 KiB
5616e0a	22.85 KiB	407.45 KiB	384.60 KiB
67460f4	20.76 KiB	426.15 KiB	405.39 KiB
3a31fc9	20.76 KiB	414.45 KiB	393.69 KiB
01a28a9	22.85 KiB	405.39 KiB	382.54 KiB
72c8d84	22.85 KiB	408.88 KiB	386.03 KiB
e324230	22.85 KiB	408.87 KiB	386.02 KiB

Previous results on branch: fix/crash-when-initializing-manually

Startup times

Revision	Plain	With Sentry	Diff
c7bedd1	1223.18 ms	1244.20 ms	21.02 ms
121d6d3	1211.39 ms	1229.22 ms	17.83 ms
6ccf54e	1238.06 ms	1239.10 ms	1.04 ms
0519fc7	1237.80 ms	1240.32 ms	2.52 ms

App size

Revision	Plain	With Sentry	Diff
c7bedd1	22.85 KiB	414.08 KiB	391.23 KiB
121d6d3	22.85 KiB	411.85 KiB	389.00 KiB
6ccf54e	22.85 KiB	413.96 KiB	391.11 KiB
0519fc7	22.85 KiB	414.08 KiB	391.23 KiB

[armcknight]

The way this is named makes me think it's retrieving something like from an ivar, but really it's creating a new thing every time it's called. Can we rename it to e.g. 'traceContextForOptions:userSegment:`?

[armcknight]

Really, I would prefer that we remove this method from SentryPropagationContext altogether and just call [[SentryTraceContext alloc] initWithTraceId:...] in the places where this method is called, I don't understand why this should be wrapped in SentryPropagationContext at all, the indirection at the call sites is confusing.

Now that most of the ivars are gone (except for self.traceId, which could just be accessed from the callsites and passed to the trace context init) it's just taking parameters and repackaging them.

[philipphofmann]

That is an excellent point. I fully I agree 🥇. I moved it.

[brustolin]

Honestly, objc is already verbose as it is, I don't think we should keeping add to it, which also increase maintenance, because if we need to change the initialisation to add/remove more attributes, we need to do it everywhere instead of one center place.

If getting traceContext from the propagation context was not good enough (because the scope is not always from the hub), we could move this function to the scope itself and get its traceContext from itself. Here is not big of a deal, this new initialisation is used only twice (for now), my fear is that we start doing this everywhere.

If the problem is the calculated property we change it to a function, no problem.

[brustolin]

LGTM

[armcknight]

LGTM, just needs a changelog update and one small fixup!