fix(android): Preserve custom Throwable identities

[sentry-junior]

Prevent R8 horizontal class merging from collapsing unrelated custom Throwable subclasses into one runtime type. This keeps captured exception types aligned with retraced constructor frames and avoids incorrect issue titles or grouping.

Consumer ProGuard rule

sentry-android-core now exports a broad rule that preserves distinct throwable class identities while still allowing unused classes to be removed and retained classes to be obfuscated:

-keep,allowshrinking,allowobfuscation class * extends java.lang.Throwable

The rule follows the mitigation recommended by the R8 maintainers.

Requested by Roman Zavarnitsyn.

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View Junior SessionSentry

[sentry]

📲 Install Builds

Android

🔗 App Name	App ID	Version	Configuration
SDK Size	io.sentry.tests.size	8.51.0 (1)	release

⚙️ sentry-android Build Distribution Settings

[github-actions]

Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	382.20 ms	455.94 ms	73.74 ms
Size	0 B	0 B	0 B

Baseline results on branch: main

Startup times

Revision	Plain	With Sentry	Diff
6b019b7	343.31 ms	417.23 ms	73.91 ms
d15471f	342.08 ms	415.44 ms	73.35 ms
8687935	332.52 ms	362.23 ms	29.71 ms
5b1a06b	352.27 ms	413.70 ms	61.43 ms
91bb874	314.47 ms	440.00 ms	125.53 ms
0ee65e9	321.06 ms	361.24 ms	40.18 ms
e63ad34	323.67 ms	390.33 ms	66.67 ms
33a08cc	267.08 ms	340.45 ms	73.37 ms
27d7cf8	397.90 ms	498.65 ms	100.75 ms
ee747ae	405.43 ms	485.70 ms	80.28 ms

App size

Revision	Plain	With Sentry	Diff
6b019b7	0 B	0 B	0 B
d15471f	1.58 MiB	2.13 MiB	559.54 KiB
8687935	1.58 MiB	2.19 MiB	619.17 KiB
5b1a06b	0 B	0 B	0 B
91bb874	1.58 MiB	2.13 MiB	559.07 KiB
0ee65e9	0 B	0 B	0 B
e63ad34	0 B	0 B	0 B
33a08cc	1.58 MiB	2.12 MiB	555.28 KiB
27d7cf8	1.58 MiB	2.12 MiB	549.42 KiB
ee747ae	1.58 MiB	2.10 MiB	530.95 KiB

[markushi]

Shouldn't this be just -keepnames (which should be short for Short for -keep,allowshrinking)?

Suggested change

	-keep,allowshrinking,allowobfuscation class * extends java.lang.Throwable
	-keepnames class * extends java.lang.Throwable

[romtsn]

I think the idea here is to allow obfuscating the class as well, and keepnames would disable that

[markushi]

We definitely need to check that R8 doesn't flag us here

[romtsn]

it likely does, but there's no other way to work this around, so 🤷 every crash reporter is prone to this issue. But I will check with the R8 config analyzer

[runningcode]

Very nice find!

[runningcode]

You said in the PR description that this was recommended by the R8 maintainers, do you have a link to that so that we can reference it in this comment?