fix(apple): make receive-cancel actually cancel the transfer

The Cancel button on an in-progress receive did nothing. CoreRepository
funnelled every core call through one serial DispatchQueue, but `receive`
is a blocking core call that occupies that queue for the whole transfer.
The tapped `cancelTransfer` was enqueued behind the in-flight `receive` on
the same serial queue, so it could never run until `receive` returned —
which it never would, because it was waiting to be cancelled. A deadlock
the button couldn't escape.

The Rust core is explicitly designed for cancel to arrive from another
thread mid-receive (VnidropCore.block_on uses a shared runtime handle for
exactly this). Extracts the two-lane dispatch into a CoreDispatcher: a
serial lane for ordered calls and a separate concurrent lane for
interrupt-style calls, and routes cancel through the latter so the signal
reaches the core and unblocks the receive.

Adds CoreDispatcherTests, including a regression guard that an interrupt
completes while the serial lane is blocked.
This commit is contained in:
2026-07-23 18:30:55 +02:00
parent 3c8267adc5
commit 081b59815c
3 changed files with 103 additions and 13 deletions

View File

@@ -21,7 +21,7 @@ final class CoreRepository: ObservableObject, CoreGateway {
// `runCore`; the underlying core is internally synchronized, so this crossing
// is safe. `nonisolated(unsafe)` documents that contract for Swift 6.
private nonisolated(unsafe) var core: VnidropCore?
private let queue = DispatchQueue(label: "com.vnidrop.core", qos: .userInitiated)
private let dispatcher = CoreDispatcher()
private lazy var sink = RepositoryEventSink { [weak self] event in
Task { @MainActor in self?.handle(event: event) }
}
@@ -119,7 +119,9 @@ final class CoreRepository: ObservableObject, CoreGateway {
// MARK: - Lifecycle actions
func cancel(transferId: UInt64) async -> Result<Void, Error> {
await runCore {
// Off the serial `queue`: a receive in flight is blocking it, and the
// cancel signal must reach the core to unblock that receive.
await runInterrupt {
try self.requireCore().cancelTransfer(transferId: transferId)
}.map { self.refreshSnapshot() }
}
@@ -253,17 +255,14 @@ final class CoreRepository: ObservableObject, CoreGateway {
/// Runs a blocking core call off the main actor and hops the result back.
private nonisolated func runCore<T: Sendable>(_ block: @escaping @Sendable () throws -> T) async -> Result<T, Error> {
await withCheckedContinuation { continuation in
queue.async {
let result: Result<T, Error>
do {
result = .success(try block())
} catch {
result = .failure(error)
}
continuation.resume(returning: result)
}
}
await dispatcher.run(block)
}
/// Like `runCore`, but off the serial lane so it can interrupt a blocking
/// call in flight there (e.g. cancel a `receive`). Only use for core calls
/// that are safe to run concurrently with another core call.
private nonisolated func runInterrupt<T: Sendable>(_ block: @escaping @Sendable () throws -> T) async -> Result<T, Error> {
await dispatcher.runInterrupt(block)
}
private nonisolated static func nextTransferId() -> UInt64 {