Alert on error: shared code (#207)

* Initial work on presenting alert on error

* Move Account-related error handling up the hierarchy

* Handle errors on logout

* Fix for temporary debugging

* Clean up WriteFreelyModel’s published vars

* Add error handling to top-level content view

* Set current error on API call failures

* Set current error on API call handlers

* Move User Defaults errors to ErrorConstants file

* Add default values for some error strings

* Handle purging post errors

* Add FIXME to track silent failure on fetching collections

As collections are fetched and added to the `list` property in the CollectionListModel’s initializer, it’s tricky to throw an error here: we call it as a property initializer in CollectionListView, which cannot throw.

Consider refactoring this logic such that we’re using, for example, a @FetchRequest in CollectionListView instead.

* Handle errors in (most) shared code

Two outliers to come back to are:

- the LocalStoreManager, where we can’t set a current error in the WriteFreelyModel in methods that can’t throw
- the CollectionListModel, where the initializer can’t throw because we use it as a property initializer in CollectionListView

* Add error handling to Mac app

* Revert "Add error handling to Mac app"

This reverts commit b1a8b8b29c.

Shared/Account/AccountLoginView.swift

@@ -2,6 +2,7 @@ import SwiftUI
 
 struct AccountLoginView: View {
     @EnvironmentObject var model: WriteFreelyModel
+    @EnvironmentObject var errorHandling: ErrorHandling
 
     @State private var alertMessage: String = ""
     @State private var username: String = ""
@@ -76,8 +77,7 @@ struct AccountLoginView: View {
                             as: username, password: password
                         )
                     } else {
-                        model.loginErrorMessage = AccountError.invalidServerURL.localizedDescription
-                        model.isPresentingLoginErrorAlert = true
+                        self.errorHandling.handle(error: AccountError.invalidServerURL)
                     }
                 }, label: {
                     Text("Log In")
@@ -88,13 +88,6 @@ struct AccountLoginView: View {
                 .padding()
             }
         }
-        .alert(isPresented: $model.isPresentingLoginErrorAlert) {
-            Alert(
-                title: Text("Error Logging In"),
-                message: Text(model.loginErrorMessage ?? "An unknown error occurred while trying to login."),
-                dismissButton: .default(Text("OK"))
-            )
-        }
     }
 }
 

Shared/Account/AccountLogoutView.swift

@@ -2,6 +2,7 @@ import SwiftUI
 
 struct AccountLogoutView: View {
     @EnvironmentObject var model: WriteFreelyModel
+    @EnvironmentObject var errorHandling: ErrorHandling
 
     @State private var isPresentingLogoutConfirmation: Bool = false
     @State private var editedPostsWarningString: String = ""
@@ -66,7 +67,7 @@ struct AccountLogoutView: View {
                 editedPostsWarningString = "You'll lose unpublished changes to \(editedPosts.count) edited posts. "
             }
         } catch {
-            print("Error: failed to fetch cached posts")
+            self.errorHandling.handle(error: LocalStoreError.couldNotFetchPosts("cached"))
         }
         self.isPresentingLogoutConfirmation = true
     }

Shared/Account/AccountModel.swift

@@ -1,58 +1,6 @@
 import SwiftUI
 import WriteFreely
 
-enum AccountError: Error {
-    case invalidPassword
-    case usernameNotFound
-    case serverNotFound
-    case invalidServerURL
-    case couldNotSaveTokenToKeychain
-    case couldNotFetchTokenFromKeychain
-    case couldNotDeleteTokenFromKeychain
-}
-
-extension AccountError: LocalizedError {
-    public var errorDescription: String? {
-        switch self {
-        case .serverNotFound:
-            return NSLocalizedString(
-                "The server could not be found. Please check the information you've entered and try again.",
-                comment: ""
-            )
-        case .invalidPassword:
-            return NSLocalizedString(
-                "Invalid password. Please check that you've entered your password correctly and try logging in again.",
-                comment: ""
-            )
-        case .usernameNotFound:
-            return NSLocalizedString(
-                "Username not found. Did you use your email address by mistake?",
-                comment: ""
-            )
-        case .invalidServerURL:
-            return NSLocalizedString(
-                "Please enter a valid instance domain name. It should look like \"https://example.com\" or \"write.as\".",  // swiftlint:disable:this line_length
-                comment: ""
-            )
-        case .couldNotSaveTokenToKeychain:
-            return NSLocalizedString(
-                "There was a problem trying to save your access token to the device, please try logging in again.",
-                comment: ""
-            )
-        case .couldNotFetchTokenFromKeychain:
-            return NSLocalizedString(
-                "There was a problem trying to fetch your access token from the device, please try logging in again.",
-                comment: ""
-            )
-        case .couldNotDeleteTokenFromKeychain:
-            return NSLocalizedString(
-                "There was a problem trying to delete your access token from the device, please try logging out again.",
-                comment: ""
-            )
-        }
-    }
-}
-
 struct AccountModel {
     @AppStorage(WFDefaults.isLoggedIn, store: UserDefaults.shared) var isLoggedIn: Bool = false
     private let defaults = UserDefaults.shared

Shared/Account/AccountView.swift

@@ -2,19 +2,33 @@ import SwiftUI
 
 struct AccountView: View {
     @EnvironmentObject var model: WriteFreelyModel
+    @EnvironmentObject var errorHandling: ErrorHandling
 
     var body: some View {
         if model.account.isLoggedIn {
             HStack {
                 Spacer()
                 AccountLogoutView()
+                    .withErrorHandling()
                 Spacer()
             }
             .padding()
         } else {
             AccountLoginView()
+                .withErrorHandling()
                 .padding(.top)
         }
+        EmptyView()
+            .onChange(of: model.hasError) { value in
+                if value {
+                    if let error = model.currentError {
+                        self.errorHandling.handle(error: error)
+                    } else {
+                        self.errorHandling.handle(error: AppError.genericError())
+                    }
+                    model.hasError = false
+                }
+            }
     }
 }
 

Shared/ErrorHandling/ErrorConstants.swift

@@ -0,0 +1,173 @@
+import Foundation
+
+// MARK: - Network Errors
+
+enum NetworkError: Error {
+    case noConnectionError
+}
+
+extension NetworkError: LocalizedError {
+    public var errorDescription: String? {
+        switch self {
+        case .noConnectionError:
+            return NSLocalizedString(
+                "There is no internet connection at the moment. Please reconnect or try again later.",
+                comment: ""
+            )
+        }
+    }
+}
+
+// MARK: - Keychain Errors
+
+enum KeychainError: Error {
+    case couldNotStoreAccessToken
+    case couldNotPurgeAccessToken
+    case couldNotFetchAccessToken
+}
+
+extension KeychainError: LocalizedError {
+    public var errorDescription: String? {
+        switch self {
+        case .couldNotStoreAccessToken:
+            return NSLocalizedString("There was a problem storing your access token in the Keychain.", comment: "")
+        case .couldNotPurgeAccessToken:
+            return NSLocalizedString("Something went wrong purging the token from the Keychain.", comment: "")
+        case .couldNotFetchAccessToken:
+            return NSLocalizedString("Something went wrong fetching the token from the Keychain.", comment: "")
+        }
+    }
+}
+
+// MARK: - Account Errors
+
+enum AccountError: Error {
+    case invalidPassword
+    case usernameNotFound
+    case serverNotFound
+    case invalidServerURL
+    case unknownLoginError
+    case genericAuthError
+}
+
+extension AccountError: LocalizedError {
+    public var errorDescription: String? {
+        switch self {
+        case .serverNotFound:
+            return NSLocalizedString(
+                "The server could not be found. Please check the information you've entered and try again.",
+                comment: ""
+            )
+        case .invalidPassword:
+            return NSLocalizedString(
+                "Invalid password. Please check that you've entered your password correctly and try logging in again.",
+                comment: ""
+            )
+        case .usernameNotFound:
+            return NSLocalizedString(
+                "Username not found. Did you use your email address by mistake?",
+                comment: ""
+            )
+        case .invalidServerURL:
+            return NSLocalizedString(
+                "Please enter a valid instance domain name. It should look like \"https://example.com\" or \"write.as\".",  // swiftlint:disable:this line_length
+                comment: ""
+            )
+        case .genericAuthError:
+            return NSLocalizedString("Something went wrong, please try logging in again.", comment: "")
+        case .unknownLoginError:
+            return NSLocalizedString("An unknown error occurred while trying to login.", comment: "")
+        }
+    }
+}
+
+// MARK: - User Defaults Errors
+
+enum UserDefaultsError: Error {
+    case couldNotMigrateStandardDefaults
+}
+
+extension UserDefaultsError: LocalizedError {
+    public var errorDescription: String? {
+        switch self {
+        case .couldNotMigrateStandardDefaults:
+            return NSLocalizedString("Could not migrate user defaults to group container", comment: "")
+        }
+    }
+}
+
+// MARK: - Local Store Errors
+
+enum LocalStoreError: Error {
+    case couldNotSaveContext
+    case couldNotFetchCollections
+    case couldNotFetchPosts(String = "")
+    case couldNotPurgePosts(String = "")
+    case couldNotPurgeCollections
+    case couldNotLoadStore(String)
+    case couldNotMigrateStore(String)
+    case couldNotDeleteStoreAfterMigration(String)
+    case genericError(String = "")
+}
+
+extension LocalStoreError: LocalizedError {
+    public var errorDescription: String? {
+        switch self {
+        case .couldNotSaveContext:
+            return NSLocalizedString("Error saving context", comment: "")
+        case .couldNotFetchCollections:
+            return NSLocalizedString("Failed to fetch blogs from local store.", comment: "")
+        case .couldNotFetchPosts(let postFilter):
+            if postFilter.isEmpty {
+                return NSLocalizedString("Failed to fetch posts from local store.", comment: "")
+            } else {
+                return NSLocalizedString("Failed to fetch \(postFilter) posts from local store.", comment: "")
+            }
+        case .couldNotPurgePosts(let postFilter):
+            if postFilter.isEmpty {
+                return NSLocalizedString("Failed to purge \(postFilter) posts from local store.", comment: "")
+            } else {
+                return NSLocalizedString("Failed to purge posts from local store.", comment: "")
+            }
+        case .couldNotPurgeCollections:
+            return NSLocalizedString("Failed to purge cached collections", comment: "")
+        case .couldNotLoadStore(let errorDescription):
+            return NSLocalizedString("Something went wrong loading local store: \(errorDescription)", comment: "")
+        case .couldNotMigrateStore(let errorDescription):
+            return NSLocalizedString("Something went wrong migrating local store: \(errorDescription)", comment: "")
+        case .couldNotDeleteStoreAfterMigration(let errorDescription):
+            return NSLocalizedString("Something went wrong deleting old store: \(errorDescription)", comment: "")
+        case .genericError(let customContent):
+            if customContent.isEmpty {
+                return NSLocalizedString("Something went wrong accessing device storage", comment: "")
+            } else {
+                return NSLocalizedString(customContent, comment: "")
+            }
+        }
+    }
+}
+
+// MARK: - Application Errors
+
+enum AppError: Error {
+    case couldNotGetLoggedInClient
+    case couldNotGetPostId
+    case genericError(String = "")
+}
+
+extension AppError: LocalizedError {
+    public var errorDescription: String? {
+        switch self {
+        case .couldNotGetLoggedInClient:
+            return NSLocalizedString("Something went wrong trying to access the WriteFreely client.", comment: "")
+        case .couldNotGetPostId:
+            return NSLocalizedString("Something went wrong trying to get the post's unique ID.", comment: "")
+        case .genericError(let customContent):
+            if customContent.isEmpty {
+                return NSLocalizedString("Something went wrong", comment: "")
+            } else {
+                return NSLocalizedString(customContent, comment: "")
+            }
+        }
+    }
+}

Shared/ErrorHandling/ErrorHandling.swift

@@ -0,0 +1,42 @@
+// Based on https://www.ralfebert.com/swiftui/generic-error-handling/
+
+import SwiftUI
+
+struct ErrorAlert: Identifiable {
+    var id = UUID()
+    var message: String
+    var dismissAction: (() -> Void)?
+}
+
+class ErrorHandling: ObservableObject {
+    @Published var currentAlert: ErrorAlert?
+
+    func handle(error: Error) {
+        currentAlert = ErrorAlert(message: error.localizedDescription)
+    }
+}
+
+struct HandleErrorByShowingAlertViewModifier: ViewModifier {
+    @StateObject var errorHandling = ErrorHandling()
+
+    func body(content: Content) -> some View {
+        content
+            .environmentObject(errorHandling)
+            .background(
+                EmptyView()
+                    .alert(item: $errorHandling.currentAlert) { currentAlert in
+                        Alert(title: Text("Error"),
+                              message: Text(currentAlert.message),
+                              dismissButton: .default(Text("OK")) {
+                            currentAlert.dismissAction?()
+                        })
+                    }
+            )
+    }
+}
+
+extension View {
+    func withErrorHandling() -> some View {
+        modifier(HandleErrorByShowingAlertViewModifier())
+    }
+}

Shared/Extensions/UserDefaults+Extensions.swift

@@ -17,17 +17,6 @@ enum WFDefaults {
 
 extension UserDefaults {
 
-    private enum DefaultsError: Error {
-        case couldNotMigrateStandardDefaults
-
-        var description: String {
-            switch self {
-            case .couldNotMigrateStandardDefaults:
-                return "Could not migrate user defaults to group container."
-            }
-        }
-    }
-
     private static let appGroupName: String = "group.com.abunchtell.writefreely"
     private static let didMigrateDefaultsToAppGroup: String = "didMigrateDefaultsToAppGroup"
     private static let didRemoveStandardDefaults: String = "didRemoveStandardDefaults"
@@ -61,7 +50,7 @@ extension UserDefaults {
             groupDefaults.set(true, forKey: UserDefaults.didMigrateDefaultsToAppGroup)
             return groupDefaults
         } else {
-            throw DefaultsError.couldNotMigrateStandardDefaults
+            throw UserDefaultsError.couldNotMigrateStandardDefaults
         }
     }
 

Shared/Extensions/WriteFreelyModel+API.swift

@@ -4,7 +4,7 @@ import WriteFreely
 extension WriteFreelyModel {
     func login(to server: URL, as username: String, password: String) {
         if !hasNetworkConnection {
-            isPresentingNetworkErrorAlert = true
+            self.currentError = NetworkError.noConnectionError
             return
         }
         let secureProtocolPrefix = "https://"
@@ -30,7 +30,7 @@ extension WriteFreelyModel {
 
     func logout() {
         if !hasNetworkConnection {
-            DispatchQueue.main.async { self.isPresentingNetworkErrorAlert = true }
+            self.currentError = NetworkError.noConnectionError
             return
         }
         guard let loggedInClient = client else {
@@ -38,7 +38,7 @@ extension WriteFreelyModel {
                 try purgeTokenFromKeychain(username: account.username, server: account.server)
                 account.logout()
             } catch {
-                fatalError("Failed to log out persisted state")
+                self.currentError = KeychainError.couldNotPurgeAccessToken
             }
             return
         }
@@ -47,10 +47,13 @@ extension WriteFreelyModel {
 
     func fetchUserCollections() {
         if !hasNetworkConnection {
-            DispatchQueue.main.async { self.isPresentingNetworkErrorAlert = true }
+            self.currentError = NetworkError.noConnectionError
+            return
+        }
+        guard let loggedInClient = client else {
+            self.currentError = AppError.couldNotGetLoggedInClient
             return
         }
-        guard let loggedInClient = client else { return }
         // We're starting the network request.
         DispatchQueue.main.async {
             self.isProcessingRequest = true
@@ -60,10 +63,13 @@ extension WriteFreelyModel {
 
     func fetchUserPosts() {
         if !hasNetworkConnection {
-            DispatchQueue.main.async { self.isPresentingNetworkErrorAlert = true }
+            self.currentError = NetworkError.noConnectionError
+            return
+        }
+        guard let loggedInClient = client else {
+            self.currentError = AppError.couldNotGetLoggedInClient
             return
         }
-        guard let loggedInClient = client else { return }
         // We're starting the network request.
         DispatchQueue.main.async {
             self.isProcessingRequest = true
@@ -75,10 +81,13 @@ extension WriteFreelyModel {
         postToUpdate = nil
 
         if !hasNetworkConnection {
-            DispatchQueue.main.async { self.isPresentingNetworkErrorAlert = true }
+            self.currentError = NetworkError.noConnectionError
+            return
+        }
+        guard let loggedInClient = client else {
+            self.currentError = AppError.couldNotGetLoggedInClient
             return
         }
-        guard let loggedInClient = client else { return }
         // We're starting the network request.
         DispatchQueue.main.async {
             self.isProcessingRequest = true
@@ -120,11 +129,17 @@ extension WriteFreelyModel {
 
     func updateFromServer(post: WFAPost) {
         if !hasNetworkConnection {
-            DispatchQueue.main.async { self.isPresentingNetworkErrorAlert = true }
+            self.currentError = NetworkError.noConnectionError
+            return
+        }
+        guard let loggedInClient = client else {
+            self.currentError = AppError.couldNotGetLoggedInClient
+            return
+        }
+        guard let postId = post.postId else {
+            self.currentError = AppError.couldNotGetPostId
             return
         }
-        guard let loggedInClient = client else { return }
-        guard let postId = post.postId else { return }
         // We're starting the network request.
         DispatchQueue.main.async {
             self.selectedPost = post
@@ -135,11 +150,17 @@ extension WriteFreelyModel {
 
     func move(post: WFAPost, from oldCollection: WFACollection?, to newCollection: WFACollection?) {
         if !hasNetworkConnection {
-            DispatchQueue.main.async { self.isPresentingNetworkErrorAlert = true }
+            self.currentError = NetworkError.noConnectionError
+            return
+        }
+        guard let loggedInClient = client else {
+            self.currentError = AppError.couldNotGetLoggedInClient
+            return
+        }
+        guard let postId = post.postId else {
+            self.currentError = AppError.couldNotGetPostId
             return
         }
-        guard let loggedInClient = client,
-              let postId = post.postId else { return }
         // We're starting the network request.
         DispatchQueue.main.async {
             self.isProcessingRequest = true

Shared/Extensions/WriteFreelyModel+APIHandlers.swift

@@ -16,33 +16,18 @@ extension WriteFreelyModel {
                     self.account.login(user)
                 }
             } catch {
-                DispatchQueue.main.async {
-                    self.loginErrorMessage = "There was a problem storing your access token to the Keychain."
-                    self.isPresentingLoginErrorAlert = true
-                }
+                self.currentError = KeychainError.couldNotStoreAccessToken
             }
         } catch WFError.notFound {
-            DispatchQueue.main.async {
-                self.loginErrorMessage = AccountError.usernameNotFound.localizedDescription
-                self.isPresentingLoginErrorAlert = true
-            }
+            self.currentError = AccountError.usernameNotFound
         } catch WFError.unauthorized {
-            DispatchQueue.main.async {
-                self.loginErrorMessage = AccountError.invalidPassword.localizedDescription
-                self.isPresentingLoginErrorAlert = true
-            }
+            self.currentError = AccountError.invalidPassword
         } catch {
             if (error as NSError).domain == NSURLErrorDomain,
                (error as NSError).code == -1003 {
-                DispatchQueue.main.async {
-                    self.loginErrorMessage = AccountError.serverNotFound.localizedDescription
-                    self.isPresentingLoginErrorAlert = true
-                }
+                self.currentError = AccountError.serverNotFound
             } else {
-                DispatchQueue.main.async {
-                    self.loginErrorMessage = error.localizedDescription
-                    self.isPresentingLoginErrorAlert = true
-                }
+                self.currentError = error
             }
         }
     }
@@ -55,11 +40,15 @@ extension WriteFreelyModel {
                 client = nil
                 DispatchQueue.main.async {
                     self.account.logout()
-                    LocalStorageManager.standard.purgeUserCollections()
-                    self.posts.purgePublishedPosts()
+                    do {
+                        try LocalStorageManager.standard.purgeUserCollections()
+                        try self.posts.purgePublishedPosts()
+                    } catch {
+                        self.currentError = error
+                    }
                 }
             } catch {
-                print("Something went wrong purging the token from the Keychain.")
+                self.currentError = KeychainError.couldNotPurgeAccessToken
             }
         } catch WFError.notFound {
             // The user token is invalid or doesn't exist, so it's been invalidated by the server. Proceed with
@@ -70,11 +59,15 @@ extension WriteFreelyModel {
                 client = nil
                 DispatchQueue.main.async {
                     self.account.logout()
-                    LocalStorageManager.standard.purgeUserCollections()
-                    self.posts.purgePublishedPosts()
+                    do {
+                        try LocalStorageManager.standard.purgeUserCollections()
+                        try self.posts.purgePublishedPosts()
+                    } catch {
+                        self.currentError = error
+                    }
                 }
             } catch {
-                print("Something went wrong purging the token from the Keychain.")
+                self.currentError = KeychainError.couldNotPurgeAccessToken
             }
         } catch {
             // We get a 'cannot parse response' (similar to what we were seeing in the Swift package) NSURLError here,
@@ -113,13 +106,10 @@ extension WriteFreelyModel {
                 LocalStorageManager.standard.saveContext()
             }
         } catch WFError.unauthorized {
-            DispatchQueue.main.async {
-                self.loginErrorMessage = "Something went wrong, please try logging in again."
-                self.isPresentingLoginErrorAlert = true
-            }
+            self.currentError = AccountError.genericAuthError
             self.logout()
         } catch {
-            print(error)
+            self.currentError = AppError.genericError(error.localizedDescription)
         }
     }
 
@@ -141,7 +131,11 @@ extension WriteFreelyModel {
                             if let fetchedPostUpdatedDate = fetchedPost.updatedDate,
                                let localPostUpdatedDate = managedPost.updatedDate {
                                 managedPost.hasNewerRemoteCopy = fetchedPostUpdatedDate > localPostUpdatedDate
-                            } else { print("Error: could not determine which copy of post is newer") }
+                            } else {
+                                self.currentError = AppError.genericError(
+                                    "Error updating post: could not determine which copy of post is newer."
+                                )
+                            }
                             postsToDelete.removeAll(where: { $0.postId == fetchedPost.postId })
                         }
                     } else {
@@ -158,16 +152,13 @@ extension WriteFreelyModel {
                     LocalStorageManager.standard.saveContext()
                 }
             } catch {
-                print(error)
+                self.currentError = AppError.genericError(error.localizedDescription)
             }
         } catch WFError.unauthorized {
-            DispatchQueue.main.async {
-                self.loginErrorMessage = "Something went wrong, please try logging in again."
-                self.isPresentingLoginErrorAlert = true
-            }
+            self.currentError = AccountError.genericAuthError
             self.logout()
         } catch {
-            print("Error: Failed to fetch cached posts")
+            self.currentError = LocalStoreError.couldNotFetchPosts("cached")
         }
     }
 
@@ -211,11 +202,11 @@ extension WriteFreelyModel {
                         LocalStorageManager.standard.saveContext()
                     }
                 } catch {
-                    print("Error: Failed to fetch cached posts")
+                    self.currentError = LocalStoreError.couldNotFetchPosts("cached")
                 }
             }
         } catch {
-            print(error)
+            self.currentError = AppError.genericError(error.localizedDescription)
         }
     }
 
@@ -237,7 +228,7 @@ extension WriteFreelyModel {
                 LocalStorageManager.standard.saveContext()
             }
         } catch {
-            print(error)
+            self.currentError = AppError.genericError(error.localizedDescription)
         }
     }
 
@@ -259,7 +250,7 @@ extension WriteFreelyModel {
             DispatchQueue.main.async {
                 LocalStorageManager.standard.container.viewContext.rollback()
             }
-            print(error)
+            self.currentError = AppError.genericError(error.localizedDescription)
         }
     }
 

Shared/Extensions/WriteFreelyModel+Keychain.swift

@@ -2,12 +2,6 @@ import Foundation
 
 extension WriteFreelyModel {
 
-    enum WFKeychainError: Error {
-        case saveToKeychainFailed
-        case purgeFromKeychainFailed
-        case fetchFromKeychainFailed
-    }
-
     func saveTokenToKeychain(_ token: String, username: String?, server: String) throws {
         let query: [String: Any] = [
             kSecClass as String: kSecClassGenericPassword,
@@ -17,7 +11,7 @@ extension WriteFreelyModel {
         ]
         let status = SecItemAdd(query as CFDictionary, nil)
         guard status == errSecDuplicateItem || status == errSecSuccess else {
-            throw WFKeychainError.saveToKeychainFailed
+            throw KeychainError.couldNotStoreAccessToken
         }
     }
 
@@ -29,7 +23,7 @@ extension WriteFreelyModel {
         ]
         let status = SecItemDelete(query as CFDictionary)
         guard status == errSecSuccess || status == errSecItemNotFound else {
-            throw WFKeychainError.purgeFromKeychainFailed
+            throw KeychainError.couldNotPurgeAccessToken
         }
     }
 
@@ -45,15 +39,15 @@ extension WriteFreelyModel {
         var secItem: CFTypeRef?
         let status = SecItemCopyMatching(query as CFDictionary, &secItem)
         guard status != errSecItemNotFound else {
-            return nil
+            throw KeychainError.couldNotFetchAccessToken
         }
         guard status == errSecSuccess else {
-            throw WFKeychainError.fetchFromKeychainFailed
+            throw KeychainError.couldNotFetchAccessToken
         }
         guard let existingSecItem = secItem as? [String: Any],
               let tokenData = existingSecItem[kSecValueData as String] as? Data,
               let token = String(data: tokenData, encoding: .utf8) else {
-            return nil
+            throw KeychainError.couldNotFetchAccessToken
         }
         return token
     }

Shared/LocalStorageManager.swift

@@ -23,19 +23,19 @@ final class LocalStorageManager {
             do {
                 try container.viewContext.save()
             } catch {
-                print("Error saving context: \(error)")
+                fatalError(LocalStoreError.couldNotSaveContext.localizedDescription)
             }
         }
     }
 
-    func purgeUserCollections() {
+    func purgeUserCollections() throws {
         let fetchRequest: NSFetchRequest<NSFetchRequestResult> = NSFetchRequest(entityName: "WFACollection")
         let deleteRequest = NSBatchDeleteRequest(fetchRequest: fetchRequest)
 
         do {
             try container.viewContext.executeAndMergeChanges(using: deleteRequest)
         } catch {
-            print("Error: Failed to purge cached collections.")
+            throw LocalStoreError.couldNotPurgeCollections
         }
     }
 
@@ -61,7 +61,7 @@ private extension LocalStorageManager {
 
         container.loadPersistentStores { _, error in
             if let error = error {
-                fatalError("Core Data store failed to load with error: \(error)")
+                fatalError(LocalStoreError.couldNotLoadStore(error.localizedDescription).localizedDescription)
             }
         }
         migrateStore(for: container)
@@ -88,14 +88,16 @@ private extension LocalStorageManager {
                                                    options: nil,
                                                    withType: NSSQLiteStoreType)
         } catch {
-            fatalError("Something went wrong migrating the store: \(error)")
+            fatalError(LocalStoreError.couldNotMigrateStore(error.localizedDescription).localizedDescription)
         }
 
         // Attempt to delete the old store.
         do {
             try FileManager.default.removeItem(at: oldStoreURL)
         } catch {
-            fatalError("Something went wrong while deleting the old store: \(error)")
+            fatalError(
+                LocalStoreError.couldNotDeleteStoreAfterMigration(error.localizedDescription).localizedDescription
+            )
         }
     }
 

Shared/Models/WriteFreelyModel.swift

@@ -6,10 +6,34 @@ import Network
 // MARK: - WriteFreelyModel
 
 final class WriteFreelyModel: ObservableObject {
+
+    // MARK: - Models
     @Published var account = AccountModel()
     @Published var preferences = PreferencesModel()
     @Published var posts = PostListModel()
     @Published var editor = PostEditorModel()
+
+    // MARK: - Error handling
+    @Published var hasError: Bool = false
+    var currentError: Error? {
+        didSet {
+            #if DEBUG
+            print("⚠️ currentError -> didSet \(currentError?.localizedDescription ?? "nil")")
+            print("  > hasError was: \(self.hasError)")
+            #endif
+            DispatchQueue.main.async {
+                #if DEBUG
+                print("  > self.currentError != nil: \(self.currentError != nil)")
+                #endif
+                self.hasError = self.currentError != nil
+                #if DEBUG
+                print("  > hasError is now: \(self.hasError)")
+                #endif
+            }
+        }
+    }
+
+    // MARK: - State
     @Published var isLoggingIn: Bool = false
     @Published var isProcessingRequest: Bool = false
     @Published var hasNetworkConnection: Bool = true
@@ -17,17 +41,13 @@ final class WriteFreelyModel: ObservableObject {
     @Published var selectedCollection: WFACollection?
     @Published var showAllPosts: Bool = true
     @Published var isPresentingDeleteAlert: Bool = false
-    @Published var isPresentingLoginErrorAlert: Bool = false
-    @Published var isPresentingNetworkErrorAlert: Bool = false
     @Published var postToDelete: WFAPost?
-    #if os(iOS)
+#if os(iOS)
     @Published var isPresentingSettingsView: Bool = false
-    #endif
+#endif
 
     static var shared = WriteFreelyModel()
 
-    var loginErrorMessage: String?
-
     // swiftlint:disable line_length
     let helpURL = URL(string: "https://discuss.write.as/c/help/5")!
     let howToURL = URL(string: "https://discuss.write.as/t/using-the-writefreely-ios-app/1946")!
@@ -48,7 +68,7 @@ final class WriteFreelyModel: ObservableObject {
             self.account.restoreState()
             if self.account.isLoggedIn {
                 guard let serverURL = URL(string: self.account.server) else {
-                    print("Server URL not found")
+                    self.currentError = AccountError.invalidServerURL
                     return
                 }
                 do {
@@ -56,8 +76,7 @@ final class WriteFreelyModel: ObservableObject {
                             username: self.account.username,
                             server: self.account.server
                     ) else {
-                        self.loginErrorMessage = AccountError.couldNotFetchTokenFromKeychain.localizedDescription
-                        self.isPresentingLoginErrorAlert = true
+                        self.currentError = KeychainError.couldNotFetchAccessToken
                         return
                     }
 
@@ -67,8 +86,8 @@ final class WriteFreelyModel: ObservableObject {
                     self.fetchUserCollections()
                     self.fetchUserPosts()
                 } catch {
-                    self.loginErrorMessage = AccountError.couldNotFetchTokenFromKeychain.localizedDescription
-                    self.isPresentingLoginErrorAlert = true
+                    self.currentError = KeychainError.couldNotFetchAccessToken
+                    return
                 }
             }
         }

Shared/Navigation/ContentView.swift

@@ -2,11 +2,13 @@ import SwiftUI
 
 struct ContentView: View {
     @EnvironmentObject var model: WriteFreelyModel
+    @EnvironmentObject var errorHandling: ErrorHandling
 
     var body: some View {
         NavigationView {
             #if os(macOS)
             CollectionListView()
+                .withErrorHandling()
                 .toolbar {
                     Button(
                         action: {
@@ -36,11 +38,13 @@ struct ContentView: View {
                 }
             #else
             CollectionListView()
+                .withErrorHandling()
             #endif
 
             #if os(macOS)
             ZStack {
                 PostListView(selectedCollection: model.selectedCollection, showAllPosts: model.showAllPosts)
+                    .withErrorHandling()
                 if model.isProcessingRequest {
                     ZStack {
                         Color(NSColor.controlBackgroundColor).opacity(0.75)
@@ -50,12 +54,23 @@ struct ContentView: View {
             }
             #else
             PostListView(selectedCollection: model.selectedCollection, showAllPosts: model.showAllPosts)
+                .withErrorHandling()
             #endif
 
             Text("Select a post, or create a new local draft.")
                 .foregroundColor(.secondary)
         }
         .environmentObject(model)
+        .onChange(of: model.hasError) { value in
+            if value {
+                if let error = model.currentError {
+                    self.errorHandling.handle(error: error)
+                } else {
+                    self.errorHandling.handle(error: AppError.genericError())
+                }
+                model.hasError = false
+            }
+        }
     }
 }
 

Shared/PostCollection/CollectionListModel.swift

@@ -19,7 +19,8 @@ class CollectionListModel: NSObject, ObservableObject {
             try collectionsController.performFetch()
             list = collectionsController.fetchedObjects ?? []
         } catch {
-            print("Failed to fetch collections!")
+            // FIXME: Errors cannot be thrown out of the CollectionListView property initializer
+            fatalError(LocalStoreError.couldNotFetchCollections.localizedDescription)
         }
     }
 }

Shared/PostCollection/CollectionListView.swift

@@ -2,6 +2,7 @@ import SwiftUI
 
 struct CollectionListView: View {
     @EnvironmentObject var model: WriteFreelyModel
+    @EnvironmentObject var errorHandling: ErrorHandling
     @ObservedObject var collections = CollectionListModel(
         managedObjectContext: LocalStorageManager.standard.container.viewContext
     )
@@ -40,6 +41,16 @@ struct CollectionListView: View {
                 self.model.editor.showAllPostsFlag = model.showAllPosts
             }
         }
+        .onChange(of: model.hasError) { value in
+            if value {
+                if let error = model.currentError {
+                    self.errorHandling.handle(error: error)
+                } else {
+                    self.errorHandling.handle(error: AppError.genericError())
+                }
+                model.hasError = false
+            }
+        }
     }
 }
 

Shared/PostList/PostListModel.swift

@@ -9,7 +9,7 @@ class PostListModel: ObservableObject {
         }
     }
 
-    func purgePublishedPosts() {
+    func purgePublishedPosts() throws {
         let fetchRequest: NSFetchRequest<NSFetchRequestResult> = NSFetchRequest(entityName: "WFAPost")
         fetchRequest.predicate = NSPredicate(format: "status != %i", 0)
         let deleteRequest = NSBatchDeleteRequest(fetchRequest: fetchRequest)
@@ -17,7 +17,7 @@ class PostListModel: ObservableObject {
         do {
             try LocalStorageManager.standard.container.viewContext.executeAndMergeChanges(using: deleteRequest)
         } catch {
-            print("Error: Failed to purge cached posts.")
+            throw LocalStoreError.couldNotPurgePosts("cached")
         }
     }
 

Shared/PostList/PostListView.swift

@@ -3,6 +3,7 @@ import Combine
 
 struct PostListView: View {
     @EnvironmentObject var model: WriteFreelyModel
+    @EnvironmentObject var errorHandling: ErrorHandling
     @Environment(\.managedObjectContext) var managedObjectContext
 
     @State private var postCount: Int = 0
@@ -86,17 +87,6 @@ struct PostListView: View {
                     Spacer()
                     Text(postCount == 1 ? "\(postCount) post" : "\(postCount) posts")
                         .foregroundColor(.secondary)
-                        .alert(isPresented: $model.isPresentingNetworkErrorAlert, content: {
-                            Alert(
-                                title: Text("Connection Error"),
-                                message: Text("""
-                                There is no internet connection at the moment. Please reconnect or try again later.
-                                """),
-                                dismissButton: .default(Text("OK"), action: {
-                                    model.isPresentingNetworkErrorAlert = false
-                                })
-                            )
-                        })
                     Spacer()
                     if model.isProcessingRequest {
                         ProgressView()
@@ -138,6 +128,16 @@ struct PostListView: View {
             model.selectedCollection = selectedCollection
             model.showAllPosts = showAllPosts
         }
+        .onChange(of: model.hasError) { value in
+            if value {
+                if let error = model.currentError {
+                    self.errorHandling.handle(error: error)
+                } else {
+                    self.errorHandling.handle(error: AppError.genericError())
+                }
+                model.hasError = false
+            }
+        }
         #else
         PostListFilteredView(
             collection: selectedCollection,
@@ -148,18 +148,6 @@ struct PostListView: View {
             ToolbarItemGroup(placement: .primaryAction) {
                 if model.selectedPost != nil {
                     ActivePostToolbarView(activePost: model.selectedPost!)
-                        .alert(isPresented: $model.isPresentingNetworkErrorAlert, content: {
-                            Alert(
-                                title: Text("Connection Error"),
-                                message: Text("""
-                                    There is no internet connection at the moment. \
-                                    Please reconnect or try again later.
-                                    """),
-                                dismissButton: .default(Text("OK"), action: {
-                                    model.isPresentingNetworkErrorAlert = false
-                                })
-                            )
-                        })
                 }
             }
         }
@@ -172,6 +160,16 @@ struct PostListView: View {
             model.selectedCollection = selectedCollection
             model.showAllPosts = showAllPosts
         }
+        .onChange(of: model.hasError) { value in
+            if value {
+                if let error = model.currentError {
+                    self.errorHandling.handle(error: error)
+                } else {
+                    self.errorHandling.handle(error: AppError.genericError())
+                }
+                model.hasError = false
+            }
+        }
         #endif
     }
 }

Shared/WriteFreely_MultiPlatformApp.swift

@@ -48,6 +48,7 @@ struct WriteFreely_MultiPlatformApp: App {
                         }
                     }
                 })
+                .withErrorHandling()
                 .environmentObject(model)
                 .environment(\.managedObjectContext, LocalStorageManager.standard.container.viewContext)
 //                .preferredColorScheme(preferences.selectedColorScheme)    // See PreferencesModel for info.

WriteFreely-MultiPlatform.xcodeproj/project.pbxproj

@@ -24,6 +24,12 @@
 		171BFDFB24D4AF8300888236 /* CollectionListView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 171BFDF924D4AF8300888236 /* CollectionListView.swift */; };
 		171DC677272C7D0B002B9B8A /* UserDefaults+Extensions.swift in Sources */ = {isa = PBXBuildFile; fileRef = 171DC676272C7D0B002B9B8A /* UserDefaults+Extensions.swift */; };
 		171DC678272C7D0B002B9B8A /* UserDefaults+Extensions.swift in Sources */ = {isa = PBXBuildFile; fileRef = 171DC676272C7D0B002B9B8A /* UserDefaults+Extensions.swift */; };
+		1727526628099802003D0A6A /* ErrorConstants.swift in Sources */ = {isa = PBXBuildFile; fileRef = 1727526528099802003D0A6A /* ErrorConstants.swift */; };
+		1727526728099802003D0A6A /* ErrorConstants.swift in Sources */ = {isa = PBXBuildFile; fileRef = 1727526528099802003D0A6A /* ErrorConstants.swift */; };
+		1727526828099802003D0A6A /* ErrorConstants.swift in Sources */ = {isa = PBXBuildFile; fileRef = 1727526528099802003D0A6A /* ErrorConstants.swift */; };
+		1727526A2809991A003D0A6A /* ErrorHandling.swift in Sources */ = {isa = PBXBuildFile; fileRef = 172752692809991A003D0A6A /* ErrorHandling.swift */; };
+		1727526B2809991A003D0A6A /* ErrorHandling.swift in Sources */ = {isa = PBXBuildFile; fileRef = 172752692809991A003D0A6A /* ErrorHandling.swift */; };
+		1727526C2809991A003D0A6A /* ErrorHandling.swift in Sources */ = {isa = PBXBuildFile; fileRef = 172752692809991A003D0A6A /* ErrorHandling.swift */; };
 		172C492E2593981900E20ADF /* MacUpdatesView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 172C492D2593981900E20ADF /* MacUpdatesView.swift */; };
 		172E10012735B83E00061372 /* UniformTypeIdentifiers.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 172E10002735B83E00061372 /* UniformTypeIdentifiers.framework */; platformFilter = maccatalyst; };
 		172E10042735B83E00061372 /* Media.xcassets in Resources */ = {isa = PBXBuildFile; fileRef = 172E10032735B83E00061372 /* Media.xcassets */; };
@@ -181,6 +187,8 @@
 		17120DB124E1E19C002B9F6C /* SettingsHeaderView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = SettingsHeaderView.swift; sourceTree = "<group>"; };
 		171BFDF924D4AF8300888236 /* CollectionListView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = CollectionListView.swift; sourceTree = "<group>"; };
 		171DC676272C7D0B002B9B8A /* UserDefaults+Extensions.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "UserDefaults+Extensions.swift"; sourceTree = "<group>"; };
+		1727526528099802003D0A6A /* ErrorConstants.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ErrorConstants.swift; sourceTree = "<group>"; };
+		172752692809991A003D0A6A /* ErrorHandling.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ErrorHandling.swift; sourceTree = "<group>"; };
 		172C492D2593981900E20ADF /* MacUpdatesView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = MacUpdatesView.swift; sourceTree = "<group>"; };
 		172E0FFF2735B83E00061372 /* ActionExtension-iOS.appex */ = {isa = PBXFileReference; explicitFileType = "wrapper.app-extension"; includeInIndex = 0; path = "ActionExtension-iOS.appex"; sourceTree = BUILT_PRODUCTS_DIR; };
 		172E10002735B83E00061372 /* UniformTypeIdentifiers.framework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.framework; name = UniformTypeIdentifiers.framework; path = System/Library/Frameworks/UniformTypeIdentifiers.framework; sourceTree = SDKROOT; };
@@ -325,6 +333,15 @@
 			path = Settings;
 			sourceTree = "<group>";
 		};
+		17275264280997BF003D0A6A /* ErrorHandling */ = {
+			isa = PBXGroup;
+			children = (
+				1727526528099802003D0A6A /* ErrorConstants.swift */,
+				172752692809991A003D0A6A /* ErrorHandling.swift */,
+			);
+			path = ErrorHandling;
+			sourceTree = "<group>";
+		};
 		172E10022735B83E00061372 /* ActionExtension-iOS */ = {
 			isa = PBXGroup;
 			children = (
@@ -476,6 +493,7 @@
 				17DF328324C87D3500BCE2E3 /* Assets.xcassets */,
 				17DF32D024C8B75C00BCE2E3 /* Account */,
 				1756AE7F24CB841200FD7257 /* Extensions */,
+				17275264280997BF003D0A6A /* ErrorHandling */,
 				1762DCB124EB07680019C4EB /* Models */,
 				17DF32CC24C8B72300BCE2E3 /* Navigation */,
 				1739B8D324EAFAB700DA7421 /* PostEditor */,
@@ -871,8 +889,10 @@
 				172E10212735C64600061372 /* WFACollection+CoreDataProperties.swift in Sources */,
 				172E101C2735C57400061372 /* LocalStorageManager.swift in Sources */,
 				172E10192735C3DB00061372 /* ContentView.swift in Sources */,
+				1727526828099802003D0A6A /* ErrorConstants.swift in Sources */,
 				172E10152735C2BD00061372 /* UIHostingView.swift in Sources */,
 				172E101F2735C64600061372 /* WFAPost+CoreDataClass.swift in Sources */,
+				1727526C2809991A003D0A6A /* ErrorHandling.swift in Sources */,
 				172E10232735C6FF00061372 /* NSManagedObjectContext+ExecuteAndMergeChanges.swift in Sources */,
 				172E101E2735C62F00061372 /* PostStatus.swift in Sources */,
 			);
@@ -887,6 +907,7 @@
 				17B37C5625C8679800FE75E9 /* WriteFreelyModel+API.swift in Sources */,
 				17C42E622507D8E600072984 /* PostStatus.swift in Sources */,
 				1756DBBA24FED45500207AB8 /* LocalStorageManager.swift in Sources */,
+				1727526A2809991A003D0A6A /* ErrorHandling.swift in Sources */,
 				1756AE8124CB844500FD7257 /* View+Keyboard.swift in Sources */,
 				17C42E652509237800072984 /* PostListFilteredView.swift in Sources */,
 				170DFA34251BBC44001D82A0 /* PostEditorModel.swift in Sources */,
@@ -912,6 +933,7 @@
 				1756DC0124FEE18400207AB8 /* WFACollection+CoreDataClass.swift in Sources */,
 				17DF32AA24C87D3500BCE2E3 /* WriteFreely_MultiPlatformApp.swift in Sources */,
 				17120DA724E19D11002B9F6C /* SettingsView.swift in Sources */,
+				1727526628099802003D0A6A /* ErrorConstants.swift in Sources */,
 				1756DC0324FEE18400207AB8 /* WFACollection+CoreDataProperties.swift in Sources */,
 				17120DA224E1985C002B9F6C /* AccountModel.swift in Sources */,
 				17120DA324E19A42002B9F6C /* PreferencesView.swift in Sources */,
@@ -937,6 +959,7 @@
 				17120DAA24E1B2F5002B9F6C /* AccountLogoutView.swift in Sources */,
 				17DF32D624C8CA3400BCE2E3 /* PostStatusBadgeView.swift in Sources */,
 				172C492E2593981900E20ADF /* MacUpdatesView.swift in Sources */,
+				1727526728099802003D0A6A /* ErrorConstants.swift in Sources */,
 				17479F152583D8E40072B7FB /* PostEditorSharingPicker.swift in Sources */,
 				17480CA6251272EE00EB7765 /* Bundle+AppVersion.swift in Sources */,
 				17C42E662509237800072984 /* PostListFilteredView.swift in Sources */,
@@ -944,6 +967,7 @@
 				17D4926727947D780035BD7E /* MacUpdatesViewModel.swift in Sources */,
 				17466626256C0D0600629997 /* MacEditorTextView.swift in Sources */,
 				170A7EC226F5186A00F1CBD4 /* CollectionListModel.swift in Sources */,
+				1727526B2809991A003D0A6A /* ErrorHandling.swift in Sources */,
 				17E5DF8A2543610700DCDC9B /* PostTextEditingView.swift in Sources */,
 				17C42E71250AAFD500072984 /* NSManagedObjectContext+ExecuteAndMergeChanges.swift in Sources */,
 				1756AE7B24CB65DF00FD7257 /* PostListView.swift in Sources */,

WriteFreely-MultiPlatform.xcodeproj/xcuserdata/angelo.xcuserdatad/xcschemes/xcschememanagement.plist

@@ -1,24 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
-<plist version="1.0">
-<dict>
-	<key>SchemeUserState</key>
-	<dict>
-		<key>ActionExtension-iOS.xcscheme_^#shared#^_</key>
-		<dict>
-			<key>orderHint</key>
-			<integer>1</integer>
-		</dict>
-		<key>WriteFreely-MultiPlatform (iOS).xcscheme_^#shared#^_</key>
-		<dict>
-			<key>orderHint</key>
-			<integer>2</integer>
-		</dict>
-		<key>WriteFreely-MultiPlatform (macOS).xcscheme_^#shared#^_</key>
-		<dict>
-			<key>orderHint</key>
-			<integer>0</integer>
-		</dict>
-	</dict>
-</dict>
-</plist>

iOS/Settings/SettingsView.swift

@@ -9,6 +9,7 @@ struct SettingsView: View {
             Form {
                 Section(header: Text("Login Details")) {
                     AccountView()
+                        .withErrorHandling()
                 }
                 Section(header: Text("Appearance")) {
                     PreferencesView(preferences: model.preferences)