feat: add method unswizzling

[philprime]

📜 Description

I adapted the method swizzling helper to keep a reference to the original implementation, so that the unswizzle methods can revert swizzling.

💡 Motivation and Context

We are introducing a new experimental flag in #4634 to conditionally swizzle Objective-C methods. Therefore some unit tests (e.g testFoo) swizzle methods, while others (e.g. testBar) do not. If we do not offer a functionality to unswizzle methods, they are leaking isolation, i.e. testFoo runs before testBar therefore methods are swizzled, even tough we don't want that.

This is required for #4634 to pass tests.

💚 How did you test it?

I added a unit test to test the unswizzling.

📝 Checklist

You have to check all boxes before merging:

• 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.
• I updated the wizard 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

• Change unswizzling to be wrapped by #if TEST to not be used in production

[github-actions]

🚨 Detected changes in high risk code 🚨

High-risk code can easily blow up and is hard to test. We had severe bugs in the past. Be extra careful when changing these files, and have an extra careful look at these:

• Sources/Sentry/SentrySwizzle.m

[github-actions]

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

Generated by 🚫 dangerJS against 4b2a0d5

[github-actions]

🚨 Detected changes in high risk code 🚨

High-risk code can easily blow up and is hard to test. We had severe bugs in the past. Be extra careful when changing these files, and have an extra careful look at these:

• Sources/Sentry/SentrySwizzle.m

[codecov]

Codecov Report

Attention: Patch coverage is 94.93671% with 4 lines in your changes missing coverage. Please review.

Project coverage is 90.633%. Comparing base (0cb72fd) to head (4b2a0d5).

Files with missing lines	Patch %	Lines
Sources/Sentry/SentrySwizzle.m	93.548%	4 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##              main     #4647       +/-   ##
=============================================
+ Coverage   90.584%   90.633%   +0.048%     
=============================================
  Files          621       621               
  Lines        71120     71201       +81     
  Branches     25306     25936      +630     
=============================================
+ Hits         64424     64532      +108     
+ Misses        6602      6573       -29     
- Partials        94        96        +2     

Files with missing lines	Coverage Δ
...ources/Sentry/include/HybridPublic/SentrySwizzle.h	97.142% <ø> (ø)
Tests/SentryTests/Helper/SentrySwizzleTests.m	92.417% <100.000%> (+0.664%)	⬆️
Sources/Sentry/SentrySwizzle.m	94.193% <93.548%> (-0.488%)	⬇️

... and 26 files with indirect coverage changes

---

Continue to review full report in Codecov by Sentry.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 0cb72fd...4b2a0d5. Read the comment docs.

[github-actions]

Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	1234.60 ms	1254.16 ms	19.56 ms
Size	22.32 KiB	761.25 KiB	738.94 KiB

Baseline results on branch: main

Startup times

Revision	Plain	With Sentry	Diff
b9a9ffd	1201.61 ms	1215.06 ms	13.45 ms
282cc99	1238.27 ms	1253.46 ms	15.19 ms
984eb2d	1220.62 ms	1235.24 ms	14.62 ms
4350d44	1228.75 ms	1246.75 ms	18.00 ms
279841c	1237.29 ms	1254.12 ms	16.83 ms
e145ca1	1207.19 ms	1230.67 ms	23.48 ms
9b9f2a0	1233.36 ms	1244.04 ms	10.68 ms
7b022df	1220.53 ms	1227.56 ms	7.03 ms
aa225e2	1218.00 ms	1236.45 ms	18.45 ms
9f0d9e0	1226.31 ms	1242.70 ms	16.40 ms

App size

Revision	Plain	With Sentry	Diff
b9a9ffd	21.58 KiB	418.43 KiB	396.85 KiB
282cc99	22.85 KiB	414.09 KiB	391.24 KiB
984eb2d	20.76 KiB	425.77 KiB	405.01 KiB
4350d44	21.58 KiB	629.82 KiB	608.24 KiB
279841c	22.84 KiB	403.19 KiB	380.34 KiB
e145ca1	21.58 KiB	669.70 KiB	648.12 KiB
9b9f2a0	21.58 KiB	707.42 KiB	685.84 KiB
7b022df	22.85 KiB	412.95 KiB	390.10 KiB
aa225e2	21.58 KiB	694.47 KiB	672.89 KiB
9f0d9e0	21.58 KiB	424.28 KiB	402.70 KiB

Previous results on branch: philprime/unswizzling

Startup times

Revision	Plain	With Sentry	Diff
1f239e8	1233.94 ms	1253.76 ms	19.82 ms

App size

Revision	Plain	With Sentry	Diff
1f239e8	22.30 KiB	760.63 KiB	738.32 KiB

[philipphofmann]

FYI, we already tried that in the past and it always blew up the tests. We instead chose a different approach: We don't unswizzle, but we make sure the operations are NoOps when closing the SDK. I mean we can try again, but we need some good reasons. What drove you to open this PR?

[philprime]

@philipphofmann in #4634 I added unit tests initializing the SentrySDK with an experimental feature flag enabled or disabled. If the SentrySDK is enabled, and swizzling happens, the swizzling remains even after closing and re-enabling the SentrySDK without swizzling.

We could also change this PR to only unswizzle in unit tests, i.e. using #if TEST

[armcknight]

What happens if something swizzles after us, and then we call this method? Do we break the call chain? I'd be interested to see a test case for that.

• some object A has a method foo
• swizzle foo and replace it with bar, which calls through to foo
• swizzle foo again and replace it with baz, which calls through to bar
• run unswizzle. does that replace baz with foo? then whatever was relying on baz is broken

If this is the case, then this is risky to ship to prod, I'd agree with @philipphofmann that at the most this should only live in test code.

[philprime]

Good catch!

I will have to further look into that and add handling for cascading swizzling. But as the main point of this PR is isolation of unit tests, I would focus on fixing that.

[brustolin]

We could also change this PR to only unswizzle in unit tests, i.e. using #if TEST

I agree with this!!

[github-actions]

🚨 Detected changes in high risk code 🚨

High-risk code can easily blow up and is hard to test. We had severe bugs in the past. Be extra careful when changing these files, and have an extra careful look at these:

• Sources/Sentry/SentrySwizzle.m