Merge branch 'relay-erase-errors'

11 files changed, 90 insertions, 152 deletions

diff --git a/ios/MullvadVPN.xcodeproj/project.pbxproj b/ios/MullvadVPN.xcodeproj/project.pbxproj
index a3b3440984..75009f9de2 100644
--- a/ios/MullvadVPN.xcodeproj/project.pbxproj
+++ b/ios/MullvadVPN.xcodeproj/project.pbxproj
@@ -45,7 +45,6 @@
 		5819C2172729595500D6EC38 /* SettingsAddDNSEntryCell.swift in Sources */ = {isa = PBXBuildFile; fileRef = 5819C2162729595500D6EC38 /* SettingsAddDNSEntryCell.swift */; };
 		5820674E26E6510200655B05 /* REST.swift in Sources */ = {isa = PBXBuildFile; fileRef = 5820674D26E6510200655B05 /* REST.swift */; };
 		5820675026E6514100655B05 /* HTTP.swift in Sources */ = {isa = PBXBuildFile; fileRef = 5820674F26E6514100655B05 /* HTTP.swift */; };
-		5820675526E6528200655B05 /* RelayCacheError.swift in Sources */ = {isa = PBXBuildFile; fileRef = 585DA87926B024F900B8C587 /* RelayCacheError.swift */; };
 		5820675626E6528A00655B05 /* RESTError.swift in Sources */ = {isa = PBXBuildFile; fileRef = 585DA88626B0277200B8C587 /* RESTError.swift */; };
 		5820675726E652A600655B05 /* REST.swift in Sources */ = {isa = PBXBuildFile; fileRef = 5820674D26E6510200655B05 /* REST.swift */; };
 		5820675826E652AF00655B05 /* RelayCacheIO.swift in Sources */ = {isa = PBXBuildFile; fileRef = 585DA87C26B0254000B8C587 /* RelayCacheIO.swift */; };
@@ -131,7 +130,6 @@
 		585CA70F25F8C44600B47C62 /* UIMetrics.swift in Sources */ = {isa = PBXBuildFile; fileRef = 585CA70E25F8C44600B47C62 /* UIMetrics.swift */; };
 		585DA87726B024A600B8C587 /* CachedRelays.swift in Sources */ = {isa = PBXBuildFile; fileRef = 585DA87626B024A600B8C587 /* CachedRelays.swift */; };
 		585DA87826B024A900B8C587 /* CachedRelays.swift in Sources */ = {isa = PBXBuildFile; fileRef = 585DA87626B024A600B8C587 /* CachedRelays.swift */; };
-		585DA87A26B024F900B8C587 /* RelayCacheError.swift in Sources */ = {isa = PBXBuildFile; fileRef = 585DA87926B024F900B8C587 /* RelayCacheError.swift */; };
 		585DA87D26B0254000B8C587 /* RelayCacheIO.swift in Sources */ = {isa = PBXBuildFile; fileRef = 585DA87C26B0254000B8C587 /* RelayCacheIO.swift */; };
 		585DA88426B0270700B8C587 /* ServerRelaysResponse.swift in Sources */ = {isa = PBXBuildFile; fileRef = 585DA88326B0270700B8C587 /* ServerRelaysResponse.swift */; };
 		585DA88526B0270700B8C587 /* ServerRelaysResponse.swift in Sources */ = {isa = PBXBuildFile; fileRef = 585DA88326B0270700B8C587 /* ServerRelaysResponse.swift */; };
@@ -440,7 +438,6 @@
 		5857F24624C882D700CF6F47 /* SelectLocationNavigationController.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = SelectLocationNavigationController.swift; sourceTree = "<group>"; };
 		585CA70E25F8C44600B47C62 /* UIMetrics.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = UIMetrics.swift; sourceTree = "<group>"; };
 		585DA87626B024A600B8C587 /* CachedRelays.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = CachedRelays.swift; sourceTree = "<group>"; };
-		585DA87926B024F900B8C587 /* RelayCacheError.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = RelayCacheError.swift; sourceTree = "<group>"; };
 		585DA87C26B0254000B8C587 /* RelayCacheIO.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = RelayCacheIO.swift; sourceTree = "<group>"; };
 		585DA88326B0270700B8C587 /* ServerRelaysResponse.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ServerRelaysResponse.swift; sourceTree = "<group>"; };
 		585DA88626B0277200B8C587 /* RESTError.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = RESTError.swift; sourceTree = "<group>"; };
@@ -746,7 +743,6 @@
 			children = (
 				585DA87626B024A600B8C587 /* CachedRelays.swift */,
 				5820675A26E6576800655B05 /* RelayCache.swift */,
-				585DA87926B024F900B8C587 /* RelayCacheError.swift */,
 				585DA87C26B0254000B8C587 /* RelayCacheIO.swift */,
 				58FB865926EA214400F188BC /* RelayCacheObserver.swift */,
 				58BFA5C522A7C97F00A6173D /* RelayCacheTracker.swift */,
@@ -1355,7 +1351,6 @@
 				5846227326E22A160035F7C2 /* AppStorePaymentObserver.swift in Sources */,
 				58F2E146276A2C9900A79513 /* StopTunnelOperation.swift in Sources */,
 				58DF5B762852108E00E92647 /* InputInjectionBuilder.swift in Sources */,
-				585DA87A26B024F900B8C587 /* RelayCacheError.swift in Sources */,
 				5856D13727450A8A00DFD627 /* UIImage+TintColor.swift in Sources */,
 				58CB0EE024B86751001EF0D8 /* RESTAPIProxy.swift in Sources */,
 				58095C532760EEC700890776 /* RESTNetworkOperation.swift in Sources */,
@@ -1530,7 +1525,6 @@
 				58F840B32464491D0044E708 /* ChainedError.swift in Sources */,
 				58D67A0A26D7AE3300557C3C /* OSLogHandler.swift in Sources */,
 				5820675626E6528A00655B05 /* RESTError.swift in Sources */,
-				5820675526E6528200655B05 /* RelayCacheError.swift in Sources */,
 				58561C9A239A5D1500BD6B5E /* IPEndpoint.swift in Sources */,
 				58781CCE22AE8918009B9D8E /* RelayConstraints.swift in Sources */,
 				581503A024D6F01E00C9C50E /* LogRotation.swift in Sources */,
diff --git a/ios/MullvadVPN/AppDelegate.swift b/ios/MullvadVPN/AppDelegate.swift
index bfdd04f016..95a32e0ffd 100644
--- a/ios/MullvadVPN/AppDelegate.swift
+++ b/ios/MullvadVPN/AppDelegate.swift
@@ -112,7 +112,7 @@ class AppDelegate: UIResponder, UIApplicationDelegate {
             }
         }
 
-        let updateRelaysOperation = ResultBlockOperation<RelayCache.FetchResult, RelayCache.Error>
+        let updateRelaysOperation = ResultBlockOperation<RelayCache.FetchResult, Error>
         { operation in
             let handle = RelayCache.Tracker.shared.updateRelays { completion in
                 operation.finish(completion: completion)
diff --git a/ios/MullvadVPN/RelayCache/RelayCacheError.swift b/ios/MullvadVPN/RelayCache/RelayCacheError.swift
deleted file mode 100644
index fe75cf2d4e..0000000000
--- a/ios/MullvadVPN/RelayCache/RelayCacheError.swift
+++ /dev/null
@@ -1,43 +0,0 @@
-//
-//  RelayCacheError.swift
-//  RelayCacheError
-//
-//  Created by pronebird on 27/07/2021.
-//  Copyright © 2021 Mullvad VPN AB. All rights reserved.
-//
-
-import Foundation
-
-extension RelayCache {
-
-    /// Error emitted by RelayCache cluster.
-    enum Error: ChainedError {
-        case readCache(Swift.Error)
-        case readPrebundledRelays(Swift.Error)
-        case decodePrebundledRelays(Swift.Error)
-        case writeCache(Swift.Error)
-        case encodeCache(Swift.Error)
-        case decodeCache(Swift.Error)
-        case rest(REST.Error)
-
-        var errorDescription: String? {
-            switch self {
-            case .encodeCache:
-                return "Encode cache error."
-            case .decodeCache:
-                return "Decode cache error."
-            case .readCache:
-                return "Read cache error."
-            case .readPrebundledRelays:
-                return "Read pre-bundled relays error."
-            case .decodePrebundledRelays:
-                return "Decode pre-bundled relays error."
-            case .writeCache:
-                return "Write cache error."
-            case .rest:
-                return "REST error."
-            }
-        }
-    }
-
-}
diff --git a/ios/MullvadVPN/RelayCache/RelayCacheIO.swift b/ios/MullvadVPN/RelayCache/RelayCacheIO.swift
index 20cbe90f6a..6a2a4deb13 100644
--- a/ios/MullvadVPN/RelayCache/RelayCacheIO.swift
+++ b/ios/MullvadVPN/RelayCache/RelayCacheIO.swift
@@ -31,31 +31,26 @@ extension RelayCache.IO {
 
     /// Safely read the cache file from disk using file coordinator.
     static func read(cacheFileURL: URL) throws -> RelayCache.CachedRelays {
-        var result: Result<RelayCache.CachedRelays, RelayCache.Error>?
+        var result: Result<RelayCache.CachedRelays, Error>?
         let fileCoordinator = NSFileCoordinator(filePresenter: nil)
 
-        let accessor = { (fileURLForReading: URL) -> Void in
-            // Decode data from disk
-            do {
+        let accessor = { (fileURLForReading: URL) in
+            result = Result {
                 let data = try Data(contentsOf: fileURLForReading)
-                let relays = try JSONDecoder().decode(RelayCache.CachedRelays.self, from: data)
-
-                result = .success(relays)
-            } catch let error as DecodingError {
-                result = .failure(.decodeCache(error))
-            } catch {
-                result = .failure(.readCache(error))
+                return try JSONDecoder().decode(RelayCache.CachedRelays.self, from: data)
             }
         }
 
         var error: NSError?
-        fileCoordinator.coordinate(readingItemAt: cacheFileURL,
-                                   options: [.withoutChanges],
-                                   error: &error,
-                                   byAccessor: accessor)
+        fileCoordinator.coordinate(
+            readingItemAt: cacheFileURL,
+            options: [.withoutChanges],
+            error: &error,
+            byAccessor: accessor
+        )
 
         if let error = error {
-            result = .failure(.readCache(error))
+            result = .failure(error)
         }
 
         return try result!.get()
@@ -69,12 +64,9 @@ extension RelayCache.IO {
         do {
             return try Self.read(cacheFileURL: cacheFileURL)
         } catch {
-            let error = error as! RelayCache.Error
-
-            switch error {
-            case .decodeCache, .readCache(CocoaError.fileReadNoSuchFile):
-                return try RelayCache.IO.readPrebundledRelays(fileURL: preBundledRelaysFileURL)
-            default:
+            if error is DecodingError || (error as? CocoaError)?.code == .fileReadNoSuchFile {
+                return try Self.readPrebundledRelays(fileURL: preBundledRelaysFileURL)
+            } else {
                 throw error
             }
         }
@@ -82,46 +74,40 @@ extension RelayCache.IO {
 
     /// Read pre-bundled relays file from disk.
     static func readPrebundledRelays(fileURL: URL) throws -> RelayCache.CachedRelays {
-        do {
-            let data = try Data(contentsOf: fileURL)
-            let relays = try REST.Coding.makeJSONDecoder()
-                .decode(REST.ServerRelaysResponse.self, from: data)
+        let data = try Data(contentsOf: fileURL)
+        let relays = try REST.Coding.makeJSONDecoder()
+            .decode(REST.ServerRelaysResponse.self, from: data)
 
-            return RelayCache.CachedRelays(
-                relays: relays,
-                updatedAt: Date(timeIntervalSince1970: 0)
-            )
-        } catch let error as DecodingError {
-            throw RelayCache.Error.decodePrebundledRelays(error)
-        } catch {
-            throw RelayCache.Error.readPrebundledRelays(error)
-        }
+        return RelayCache.CachedRelays(
+            relays: relays,
+            updatedAt: Date(timeIntervalSince1970: 0)
+        )
     }
 
     /// Safely write the cache file on disk using file coordinator.
     static func write(cacheFileURL: URL, record: RelayCache.CachedRelays) throws {
-        var resultError: RelayCache.Error?
+        var result: Result<(), Error>?
         let fileCoordinator = NSFileCoordinator(filePresenter: nil)
 
-        let accessor = { (fileURLForWriting: URL) -> Void in
-            do {
+        let accessor = { (fileURLForWriting: URL) in
+            result = Result {
                 let data = try JSONEncoder().encode(record)
                 try data.write(to: fileURLForWriting)
-            } catch let error as EncodingError {
-                resultError = .encodeCache(error)
-            } catch {
-                resultError = .writeCache(error)
             }
         }
 
         var error: NSError?
-        fileCoordinator.coordinate(writingItemAt: cacheFileURL,
-                                   options: [.forReplacing],
-                                   error: &error,
-                                   byAccessor: accessor)
+        fileCoordinator.coordinate(
+            writingItemAt: cacheFileURL,
+            options: [.forReplacing],
+            error: &error,
+            byAccessor: accessor
+        )
 
-        if let resultError = resultError {
-            throw resultError
+        if let error = error {
+            result = .failure(error)
         }
+
+        try result?.get()
     }
 }
diff --git a/ios/MullvadVPN/RelayCache/RelayCacheTracker.swift b/ios/MullvadVPN/RelayCache/RelayCacheTracker.swift
index f7ffcf2f72..702e5b9273 100644
--- a/ios/MullvadVPN/RelayCache/RelayCacheTracker.swift
+++ b/ios/MullvadVPN/RelayCache/RelayCacheTracker.swift
@@ -35,6 +35,12 @@ extension RelayCache {
         }
     }
 
+    struct NoCachedRelaysError: LocalizedError {
+        var errorDescription: String? {
+            return "Relay cache is empty."
+        }
+    }
+
     class Tracker {
         /// Relay update interval (in seconds).
         static let relayUpdateInterval: TimeInterval = 60 * 60
@@ -134,14 +140,14 @@ extension RelayCache {
 
         func updateRelays(
             completionHandler: (
-                (OperationCompletion<RelayCache.FetchResult, RelayCache.Error>) -> Void
+                (OperationCompletion<RelayCache.FetchResult, Error>) -> Void
             )? = nil
         ) -> Cancellable
         {
-            let operation = ResultBlockOperation<RelayCache.FetchResult, RelayCache.Error>(
+            let operation = ResultBlockOperation<RelayCache.FetchResult, Error>(
                 dispatchQueue: nil
             ) { operation in
-                let cachedRelays = self.getCachedRelays()
+                let cachedRelays = try? self.getCachedRelays()
 
                 if self.getNextUpdateDate() > Date() {
                     operation.finish(completion: .success(.throttled))
@@ -174,11 +180,15 @@ extension RelayCache {
             return operation
         }
 
-        func getCachedRelays() -> CachedRelays? {
+        func getCachedRelays() throws -> CachedRelays {
             nslock.lock()
             defer { nslock.unlock() }
 
-            return cachedRelays
+            if let cachedRelays = cachedRelays {
+                return cachedRelays
+            } else {
+                throw NoCachedRelaysError()
+            }
         }
 
         func getNextUpdateDate() -> Date {
@@ -214,28 +224,23 @@ extension RelayCache {
 
         private func handleResponse(
             completion: OperationCompletion<REST.ServerRelaysCacheResponse, REST.Error>
-        ) -> OperationCompletion<FetchResult, RelayCache.Error>
+        ) -> OperationCompletion<FetchResult, Error>
         {
-            let mappedCompletion = completion
-                .mapError { error -> RelayCache.Error in
-                    return .rest(error)
-                }
-                .tryMap { response -> FetchResult in
-                    switch response {
-                    case .newContent(let etag, let relays):
-                        try self.storeResponse(etag: etag, relays: relays)
+            let mappedCompletion = completion.tryMap { response -> FetchResult in
+                switch response {
+                case .newContent(let etag, let relays):
+                    try self.storeResponse(etag: etag, relays: relays)
 
-                        return .newContent
+                    return .newContent
 
-                    case .notModified:
-                        return .sameContent
-                    }
+                case .notModified:
+                    return .sameContent
                 }
-                .assertFailure(RelayCache.Error.self)
+            }
 
             if let error = mappedCompletion.error {
                 logger.error(
-                    chainedError: error,
+                    chainedError: AnyChainedError(error),
                     message: "Failed to update relays."
                 )
             }
@@ -258,24 +263,16 @@ extension RelayCache {
             cachedRelays = newCachedRelays
             nslock.unlock()
 
+            try RelayCache.IO.write(
+                cacheFileURL: cacheFileURL,
+                record: newCachedRelays
+            )
+
             DispatchQueue.main.async {
                 self.observerList.forEach { observer in
                     observer.relayCache(self, didUpdateCachedRelays: newCachedRelays)
                 }
             }
-
-            do {
-                try RelayCache.IO.write(
-                    cacheFileURL: cacheFileURL,
-                    record: newCachedRelays
-                )
-            } catch {
-                logger.error(
-                    chainedError: AnyChainedError(error),
-                    message: "Failed to store downloaded relays."
-                )
-                throw error
-            }
         }
 
 
diff --git a/ios/MullvadVPN/RelaySelector.swift b/ios/MullvadVPN/RelaySelector.swift
index 5e7492ca16..c29c8ccef5 100644
--- a/ios/MullvadVPN/RelaySelector.swift
+++ b/ios/MullvadVPN/RelaySelector.swift
@@ -32,17 +32,23 @@ extension RelaySelectorResult {
     }
 }
 
+struct NoRelaysSatisfyingConstraintsError: LocalizedError {
+    var errorDescription: String? {
+        return "No relays satisfying constraints."
+    }
+}
+
 enum RelaySelector {}
 
 extension RelaySelector {
 
-    static func evaluate(relays: REST.ServerRelaysResponse, constraints: RelayConstraints) -> RelaySelectorResult? {
+    static func evaluate(relays: REST.ServerRelaysResponse, constraints: RelayConstraints) throws -> RelaySelectorResult {
         let filteredRelays = applyConstraints(constraints, relays: Self.parseRelaysResponse(relays))
 
         guard let relayWithLocation = pickRandomRelay(relays: filteredRelays),
               let port = pickRandomPort(rawPortRanges: relays.wireguard.portRanges) else {
-                  return nil
-              }
+            throw NoRelaysSatisfyingConstraintsError()
+        }
 
         let endpoint = MullvadEndpoint(
             ipv4Relay: IPv4Endpoint(
diff --git a/ios/MullvadVPN/SceneDelegate.swift b/ios/MullvadVPN/SceneDelegate.swift
index 00c8a2ce3e..56e6d1e8bc 100644
--- a/ios/MullvadVPN/SceneDelegate.swift
+++ b/ios/MullvadVPN/SceneDelegate.swift
@@ -324,7 +324,7 @@ extension SceneDelegate {
         let selectLocationController = SelectLocationViewController()
         selectLocationController.delegate = self
 
-        if let cachedRelays = RelayCache.Tracker.shared.getCachedRelays() {
+        if let cachedRelays = try? RelayCache.Tracker.shared.getCachedRelays() {
             selectLocationController.setCachedRelays(cachedRelays)
         }
 
diff --git a/ios/MullvadVPN/SimulatorTunnelProviderHost.swift b/ios/MullvadVPN/SimulatorTunnelProviderHost.swift
index 975eb98ab4..d523e499fb 100644
--- a/ios/MullvadVPN/SimulatorTunnelProviderHost.swift
+++ b/ios/MullvadVPN/SimulatorTunnelProviderHost.swift
@@ -83,7 +83,7 @@ class SimulatorTunnelProviderHost: SimulatorTunnelProviderDelegate {
     }
 
     private func pickRelay() -> RelaySelectorResult? {
-        guard let cachedRelays = RelayCache.Tracker.shared.getCachedRelays() else {
+        guard let cachedRelays = try? RelayCache.Tracker.shared.getCachedRelays() else {
             providerLogger.error("Failed to obtain relays when picking relay.")
             return nil
         }
@@ -91,7 +91,7 @@ class SimulatorTunnelProviderHost: SimulatorTunnelProviderDelegate {
         do {
             let tunnelSettings = try SettingsManager.readSettings()
 
-            return RelaySelector.evaluate(
+            return try RelaySelector.evaluate(
                 relays: cachedRelays.relays,
                 constraints: tunnelSettings.relayConstraints
             )
diff --git a/ios/MullvadVPN/TunnelManager/StartTunnelOperation.swift b/ios/MullvadVPN/TunnelManager/StartTunnelOperation.swift
index 9723e29863..2ffa3cb9d6 100644
--- a/ios/MullvadVPN/TunnelManager/StartTunnelOperation.swift
+++ b/ios/MullvadVPN/TunnelManager/StartTunnelOperation.swift
@@ -45,7 +45,7 @@ class StartTunnelOperation: ResultOperation<(), TunnelManager.Error> {
             finish(completion: .success(()))
 
         case .disconnected, .pendingReconnect:
-            guard let cachedRelays = RelayCache.Tracker.shared.getCachedRelays() else {
+            guard let cachedRelays = try? RelayCache.Tracker.shared.getCachedRelays() else {
                 finish(completion: .failure(.readRelays))
                 return
             }
@@ -62,12 +62,10 @@ class StartTunnelOperation: ResultOperation<(), TunnelManager.Error> {
     }
 
     private func didReceiveRelays(tunnelSettings: TunnelSettingsV2, cachedRelays: RelayCache.CachedRelays) {
-        let selectorResult = RelaySelector.evaluate(
+        guard let selectorResult = try? RelaySelector.evaluate(
             relays: cachedRelays.relays,
             constraints: tunnelSettings.relayConstraints
-        )
-
-        guard let selectorResult = selectorResult else {
+        ) else {
             finish(completion: .failure(.cannotSatisfyRelayConstraints))
             return
         }
diff --git a/ios/MullvadVPNTests/RelaySelectorTests.swift b/ios/MullvadVPNTests/RelaySelectorTests.swift
index 10dcb8502e..8f997289db 100644
--- a/ios/MullvadVPNTests/RelaySelectorTests.swift
+++ b/ios/MullvadVPNTests/RelaySelectorTests.swift
@@ -11,27 +11,27 @@ import Network
 
 class RelaySelectorTests: XCTestCase {
 
-    func testCountryConstraint() {
+    func testCountryConstraint() throws {
         let constraints = RelayConstraints(location: .only(.country("es")))
 
-        let result = RelaySelector.evaluate(relays: sampleRelays, constraints: constraints)
+        let result = try RelaySelector.evaluate(relays: sampleRelays, constraints: constraints)
 
-        XCTAssertEqual(result?.relay.hostname, "es1-wireguard")
+        XCTAssertEqual(result.relay.hostname, "es1-wireguard")
     }
 
-    func testCityConstraint() {
+    func testCityConstraint() throws {
         let constraints = RelayConstraints(location: .only(.city("se", "got")))
-        let result = RelaySelector.evaluate(relays: sampleRelays, constraints: constraints)
+        let result = try RelaySelector.evaluate(relays: sampleRelays, constraints: constraints)
 
-        XCTAssertEqual(result?.relay.hostname, "se10-wireguard")
+        XCTAssertEqual(result.relay.hostname, "se10-wireguard")
     }
 
-    func testHostnameConstraint() {
+    func testHostnameConstraint() throws {
         let constraints = RelayConstraints(location: .only(.hostname("se", "sto", "se6-wireguard")))
 
-        let result = RelaySelector.evaluate(relays: sampleRelays, constraints: constraints)
+        let result = try RelaySelector.evaluate(relays: sampleRelays, constraints: constraints)
 
-        XCTAssertEqual(result?.relay.hostname, "se6-wireguard")
+        XCTAssertEqual(result.relay.hostname, "se6-wireguard")
     }
 
 }
diff --git a/ios/PacketTunnel/PacketTunnelProvider.swift b/ios/PacketTunnel/PacketTunnelProvider.swift
index 2e917eb5b1..126ed7b6ae 100644
--- a/ios/PacketTunnel/PacketTunnelProvider.swift
+++ b/ios/PacketTunnel/PacketTunnelProvider.swift
@@ -420,7 +420,7 @@ class PacketTunnelProvider: NEPacketTunnelProvider, TunnelMonitorDelegate {
             throw PacketTunnelProviderError.readRelayCache(error)
         }
 
-        if let selectorResult = RelaySelector.evaluate(
+        if let selectorResult = try? RelaySelector.evaluate(
             relays: cachedRelayList.relays,
             constraints: relayConstraints
         ) {