Refine errors presented to the user

Author: allenhumphreys

ConfCore/Resource+Error.swift

@@ -9,21 +9,53 @@
 import Foundation
 import Siesta
 
-public enum APIError: Error {
+public enum APIError: Error, CustomNSError {
     case http(Error)
     case adapter
     case unknown
 
     public var localizedDescription: String {
         switch self {
-        case .http(let error):
+        case let .http(error as RequestError):
+            return error.userMessage
+        case let .http(error):
             return error.localizedDescription
         case .adapter:
             return "Unable to process the data returned by the server"
         case .unknown:
             return "An unknown networking error occurred"
         }
     }
+
+    public static var errorDomain: String {
+        return "io.wwdc.error"
+    }
+
+    public var errorCode: Int {
+        switch self {
+        case .http: return 0
+        case .adapter: return 1
+        case .unknown: return 2
+        }
+    }
+
+    /// The user-info dictionary.
+    public var errorUserInfo: [String: Any] {
+        var userInfo = [NSLocalizedDescriptionKey: localizedDescription]
+
+        switch self {
+        case let .http(underlying as RequestError) where underlying.cause != nil && (underlying.cause! as NSError).domain == NSURLErrorDomain:
+            let underlyingUserInfo = (underlying.cause! as NSError).userInfo.compactMapValues { $0 as? String }
+            userInfo.merge(underlyingUserInfo, uniquingKeysWith: { $1 })
+            userInfo[NSLocalizedRecoverySuggestionErrorKey] = "Please try again"
+        case let .http(underlying as RequestError) where underlying.cause != nil && underlying.cause! is DecodingError:
+            userInfo[NSLocalizedRecoverySuggestionErrorKey] = "Please report this error"
+        case .adapter, .unknown, .http:
+            ()
+        }
+
+        return userInfo
+    }
 }
 
 extension Resource {

ConfCore/Storage.swift

@@ -84,26 +84,23 @@ public final class Storage {
     }
 
     func store(contentResult: Result<ContentsResponse, APIError>, completion: @escaping (Error?) -> Void) {
-        if case let .failure(error) = contentResult {
-            os_log("Error downloading contents: %{public}@",
+        let contentsResponse: ContentsResponse
+        do {
+            contentsResponse = try contentResult.get()
+        } catch {
+            os_log("Error downloading contents:\n%{public}@",
                    log: log,
                    type: .error,
                    String(describing: error))
-
             completion(error)
-
-            return
-        }
-
-        guard case let .success(sessionsResponse) = contentResult else {
             return
         }
 
         performSerializedBackgroundWrite(writeBlock: { backgroundRealm in
-            sessionsResponse.sessions.forEach { newSession in
+            contentsResponse.sessions.forEach { newSession in
                 // Replace any "unknown" resources with their full data
                 newSession.related.filter({$0.type == RelatedResourceType.unknown.rawValue}).forEach { unknownResource in
-                    if let fullResource = sessionsResponse.resources.filter({$0.identifier == unknownResource.identifier}).first {
+                    if let fullResource = contentsResponse.resources.filter({$0.identifier == unknownResource.identifier}).first {
                         newSession.related.replace(index: newSession.related.index(of: unknownResource)!, object: fullResource)
                     }
                 }
@@ -117,7 +114,7 @@ public final class Storage {
             }
 
             // Merge existing instance data, preserving user-defined data
-            sessionsResponse.instances.forEach { newInstance in
+            contentsResponse.instances.forEach { newInstance in
                 if let existingInstance = backgroundRealm.object(ofType: SessionInstance.self, forPrimaryKey: newInstance.identifier) {
                     existingInstance.merge(with: newInstance, in: backgroundRealm)
                 } else {
@@ -134,9 +131,9 @@ public final class Storage {
             }
 
             // Save everything
-            backgroundRealm.add(sessionsResponse.rooms, update: true)
-            backgroundRealm.add(sessionsResponse.tracks, update: true)
-            backgroundRealm.add(sessionsResponse.events, update: true)
+            backgroundRealm.add(contentsResponse.rooms, update: true)
+            backgroundRealm.add(contentsResponse.tracks, update: true)
+            backgroundRealm.add(contentsResponse.events, update: true)
 
             // add instances to rooms
             backgroundRealm.objects(Room.self).forEach { room in
@@ -225,7 +222,16 @@ public final class Storage {
     }
 
     internal func store(liveVideosResult: Result<[SessionAsset], APIError>) {
-        guard case .success(let assets) = liveVideosResult else { return }
+        let assets: [SessionAsset]
+        do {
+            assets = try liveVideosResult.get()
+        } catch {
+            os_log("Error downloading live videos:\n%{public}@",
+                   log: log,
+                   type: .error,
+                   String(describing: error))
+            return
+        }
 
         performSerializedBackgroundWrite(writeBlock: { [weak self] backgroundRealm in
             guard let self = self else { return }
@@ -251,19 +257,18 @@ public final class Storage {
     }
 
     internal func store(featuredSectionsResult: Result<[FeaturedSection], APIError>, completion: @escaping (Error?) -> Void) {
-        if case let .failure(error) = featuredSectionsResult {
-            os_log("Error downloading featured sections: %{public}@",
+        let sections: [FeaturedSection]
+        do {
+            sections = try featuredSectionsResult.get()
+        } catch {
+            os_log("Error downloading featured sections:\n%{public}@",
                    log: log,
                    type: .error,
                    String(describing: error))
-
             completion(error)
-
             return
         }
 
-        guard case .success(let sections) = featuredSectionsResult else { return }
-
         performSerializedBackgroundWrite(writeBlock: { backgroundRealm in
             let existingSections = backgroundRealm.objects(FeaturedSection.self)
             for section in existingSections {

WWDC/AppCoordinator.swift

@@ -316,15 +316,15 @@ final class AppCoordinator {
 
         _ = NotificationCenter.default.addObserver(forName: .SyncEngineDidSyncSessionsAndSchedule, object: nil, queue: .main) { note in
             if let error = note.object as? Error {
-                NSApp.presentError(error)
+                WWDCAlert.show(with: error)
             } else {
                 self.updateListsAfterSync(migrate: true)
             }
         }
 
         _ = NotificationCenter.default.addObserver(forName: .SyncEngineDidSyncFeaturedSections, object: nil, queue: .main) { note in
             if let error = note.object as? Error {
-                NSApp.presentError(error)
+                WWDCAlert.show(with: error)
             } else {
                 self.updateFeaturedSectionsAfterSync()
             }