Fixes discovered while porting Namecoin NIP-05 to Primal Android
(PrimalHQ/primal-android-app#934):
1. Race condition: stale intermediate lookups overwrite final result
- Changed map to mapLatest in SearchBarViewModel so that previous
in-flight ElectrumX lookups are cancelled when the query changes
- Without this, typing 'd/testls' character by character causes
stale results from 'd/test', 'd/testl' etc. to arrive after
the correct 'd/testls' result and overwrite it with null
2. CancellationException swallowed in catch block
- mapLatest cancels previous coroutines via CancellationException
- The generic catch was catching it and emitting null, wiping the
valid result. Now re-throws CancellationException
3. Root lookup fails when names object has no underscore key
- extractFromDomainValue tried names[localPart] then names[underscore]
which is the same thing for root lookups
- Now falls back to first available entry for root lookups when
no underscore key exists
- Non-root lookups still fail correctly (no false matches)
4. Global Mutex serializes all lookups
- Single Mutex in ElectrumxClient blocked unrelated lookups to
different servers. A 25s timeout on one server stalled everything
- Now uses per-server mutexes via ConcurrentHashMap
5. customServers set but never read
- NamecoinNameService.setCustomServers() stored the list but the
resolver was constructed with the default serverListProvider
- Now wires customServers through to the resolver
6. resolveLive uses orphaned CoroutineScope
- Now accepts an optional external scope parameter so callers can
tie resolution to their own lifecycle
Adds 2 new tests: root fallback to first entry, non-root no-fallback.
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