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

Shared/Extensions/WriteFreelyModel+APIHandlers.swift

@@ -40,8 +40,8 @@ extension WriteFreelyModel {
                 client = nil
                 DispatchQueue.main.async {
                     self.account.logout()
-                    LocalStorageManager.standard.purgeUserCollections()
                     do {
+                        try LocalStorageManager.standard.purgeUserCollections()
                         try self.posts.purgePublishedPosts()
                     } catch {
                         self.currentError = error
@@ -59,8 +59,8 @@ extension WriteFreelyModel {
                 client = nil
                 DispatchQueue.main.async {
                     self.account.logout()
-                    LocalStorageManager.standard.purgeUserCollections()
                     do {
+                        try LocalStorageManager.standard.purgeUserCollections()
                         try self.posts.purgePublishedPosts()
                     } catch {
                         self.currentError = error

Shared/LocalStorageManager.swift

@@ -23,19 +23,19 @@ final class LocalStorageManager {
             do {
                 try container.viewContext.save()
             } catch {
-                print(LocalStoreError.couldNotSaveContext.localizedDescription)
+                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(LocalStoreError.couldNotPurgeCollections.localizedDescription)
+            throw LocalStoreError.couldNotPurgeCollections
         }
     }
 

Shared/PostCollection/CollectionListModel.swift

@@ -20,7 +20,7 @@ class CollectionListModel: NSObject, ObservableObject {
             list = collectionsController.fetchedObjects ?? []
         } catch {
             // FIXME: Errors cannot be thrown out of the CollectionListView property initializer
-            print("Failed to fetch collections!")
+            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
+            }
+        }
     }
 }