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Improve reliability of online/offline detection when fetching dependencies #9378

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Improve reliability of online/offline detection when fetching dependencies #9378

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54 changes: 12 additions & 42 deletions Sources/SourceControl/RepositoryManager.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -46,7 +46,7 @@ public class RepositoryManager: Cancellable {
// Limits how many concurrent operations can be performed at once.
private let asyncOperationQueue: AsyncOperationQueue

private var emitNoConnectivityWarning = ThreadSafeBox<Bool>(true)
private var emitNoConnectivityWarning = ThreadSafeBox<[String: Bool]>([:])

/// Create a new empty manager.
///
Expand Down Expand Up @@ -343,9 +343,11 @@ public class RepositoryManager: Cancellable {
// If we are offline and have a valid cached repository, use the cache anyway.
if try isOffline(error) && self.provider.isValidDirectory(cachedRepositoryPath, for: handle.repository) {
// For the first offline use in the lifetime of this repository manager, emit a warning.
if self.emitNoConnectivityWarning.get(default: false) {
self.emitNoConnectivityWarning.put(false)
observabilityScope.emit(warning: "no connectivity, using previously cached repository state")
var warningState = self.emitNoConnectivityWarning.get(default: [:])
if !(warningState[handle.repository.url] ?? false) {
warningState[handle.repository.url] = true
self.emitNoConnectivityWarning.put(warningState)
observabilityScope.emit(warning: "no connectivity to \(handle.repository.url), using previously cached repository state")
}
observabilityScope.emit(info: "using previously cached repository state for \(package)")

Expand Down Expand Up @@ -645,45 +647,13 @@ extension RepositorySpecifier {
}
}

#if canImport(SystemConfiguration)
import SystemConfiguration

private struct Reachability {
let reachability: SCNetworkReachability

init?() {
var emptyAddress = sockaddr()
emptyAddress.sa_len = UInt8(MemoryLayout<sockaddr>.size)
emptyAddress.sa_family = sa_family_t(AF_INET)

guard let reachability = withUnsafePointer(to: &emptyAddress, {
SCNetworkReachabilityCreateWithAddress(nil, UnsafePointer($0))
}) else {
return nil
}
self.reachability = reachability
}

var connectionRequired: Bool {
var flags = SCNetworkReachabilityFlags()
let hasFlags = withUnsafeMutablePointer(to: &flags) {
SCNetworkReachabilityGetFlags(reachability, UnsafeMutablePointer($0))
}
guard hasFlags else { return false }
guard flags.contains(.reachable) else {
return true
}
return flags.contains(.connectionRequired) || flags.contains(.transientConnection)
}
}

fileprivate func isOffline(_ error: Swift.Error) -> Bool {
return Reachability()?.connectionRequired == true
}
#else
/// This used to rely on the SCNetworkReachability APIs on Darwin platforms and
/// the string match elsewhere, however SCNetworkReachability has not been recommended
/// to determine online/offline status. Instead do a simple string match on the error
/// message indicating the host could not be resolved.
/// This may falsely report offline status if the host is down, but this is effectively
/// equivalent from the user's perspective.
fileprivate func isOffline(_ error: Swift.Error) -> Bool {
// TODO: Find a better way to determine reachability on non-Darwin platforms.
return "\(error)".contains("Could not resolve host")
}
#endif