RJS-2784 Fix callback crashes when reloading with React Native

[danieltabacaru]

What, How & Why?

See realm/realm-js#6579 and realm/realm-js#6824
When hot reloading with React Native and using sync session connection change callbacks, the app crashes. This is because the callbacks are not cleared and get called. This PR unregisters all callbacks set through the SyncSession when the SyncManager is destroyed as a result of the App being destroyed.

Fixes realm/realm-js#6579.

☑️ ToDos

• 📝 Changelog update
• 🚦 Tests (or not relevant)
• C-API, if public C++ API changed
• bindgen/spec.yml, if public C++ API changed

[tgoyne]

Shouldn't this be sending OperationCancelled to any subscription change notifications?

[danieltabacaru]

my reasoning was to guard against sub.get_state_change_notification().get_async() use cases.

[tgoyne]

Yes, that needs to invoke the completion handler. Every Future must always be fulfilled.

[danieltabacaru]

but the completion handler may be gone and crash (pretty much the issue with every handler/callback).

[tgoyne]

The JS SDK needs to either ensure that App is destroyed before the callback handlers or take responsibility for discarding OperationCancelled calls. The Promise being destroyed without being fulfilled will invoke the completion handler with a BrokenPromise error if we don't explicitly fulfill it.

[danieltabacaru]

I see. I will revert this specific change then cc @gagik

[coveralls-official]

Pull Request Test Coverage Report for Build daniel.tabacaru_887

Details

• 35 of 37 (94.59%) changed or added relevant lines in 2 files are covered.
• 294 unchanged lines in 9 files lost coverage.
• Overall coverage increased (+0.02%) to 91.108%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
test/object-store/sync/session/connection_change_notifications.cpp	14	16	87.5%

Files with Coverage Reduction	New Missed Lines	%
src/realm/sync/noinst/client_impl_base.cpp	1	82.88%
test/fuzz_tester.hpp	1	57.73%
src/realm/sync/changeset.cpp	2	39.15%
test/object-store/util/test_file.cpp	2	86.47%
src/realm/table.cpp	3	90.59%
src/realm/sync/noinst/protocol_codec.cpp	8	82.51%
src/realm/sync/noinst/server/server.cpp	19	74.02%
test/test_sync.cpp	114	93.03%
src/realm/query_conditions.hpp	144	69.04%

Totals
Change from base Build 2554:	0.02%
Covered Lines:	217072
Relevant Lines:	238259

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💛 - Coveralls