Fix crash when fetching attachment data fails

Tusker/Models/CompositionAttachmentData.swift

@@ -48,13 +48,13 @@ enum CompositionAttachmentData {
         }
     }
     
-    func getData(completion: @escaping (_ data: Data, _ mimeType: String) -> Void) {
+    func getData(completion: @escaping (Result<(Data, String), Error>) -> Void) {
         switch self {
         case let .image(image):
             // Export as JPEG instead of PNG, otherweise photos straight from the camera are too large
             // for Mastodon in its default configuration (max of 10MB).
             // The quality of 0.8 was chosen completely arbitrarily, it may need to be tuned in the future.
-            completion(image.jpegData(compressionQuality: 0.8)!, "image/jpeg")
+            completion(.success((image.jpegData(compressionQuality: 0.8)!, "image/jpeg")))
         case let .asset(asset):
             if asset.mediaType == .image {
                 let options = PHImageRequestOptions()
@@ -63,7 +63,10 @@ enum CompositionAttachmentData {
                 options.resizeMode = .none
                 options.isNetworkAccessAllowed = true
                 PHImageManager.default().requestImageDataAndOrientation(for: asset, options: options) { (data, dataUTI, orientation, info) in
-                    guard var data = data, let dataUTI = dataUTI else { fatalError() }
+                    guard var data = data, let dataUTI = dataUTI else {
+                        completion(.failure(.missingData))
+                        return
+                    }
     
                     let mimeType: String
                     if dataUTI == "public.heic" {
@@ -77,7 +80,7 @@ enum CompositionAttachmentData {
                         mimeType = UTType(dataUTI)!.preferredMIMEType!
                     }
     
-                    completion(data, mimeType)
+                    completion(.success((data, mimeType)))
                 }
             } else if asset.mediaType == .video {
                 let options = PHVideoRequestOptions()
@@ -100,20 +103,23 @@ enum CompositionAttachmentData {
             
         case let .drawing(drawing):
             let image = drawing.imageInLightMode(from: drawing.bounds, scale: 1)
-            completion(image.pngData()!, "image/png")
+            completion(.success((image.pngData()!, "image/png")))
         }
     }
     
-    private static func exportVideoData(session: AVAssetExportSession, completion: @escaping (Data, String) -> Void) {
+    private static func exportVideoData(session: AVAssetExportSession, completion: @escaping (Result<(Data, String), Error>) -> Void) {
         session.outputFileType = .mp4
         session.outputURL = FileManager.default.temporaryDirectory.appendingPathComponent("exported_video_\(UUID())").appendingPathExtension("mp4")
         session.exportAsynchronously {
-            guard session.status == .completed else { fatalError("video export failed: \(String(describing: session.error))") }
+            guard session.status == .completed else {
+                completion(.failure(.export(session.error!)))
+                return
+            }
             do {
                 let data = try Data(contentsOf: session.outputURL!)
-                completion(data, "video/mp4")
+                completion(.success((data, "video/mp4")))
             } catch {
-                fatalError("Unable to load video: \(error)")
+                completion(.failure(.export(error)))
             }
         }
     }
@@ -121,6 +127,11 @@ enum CompositionAttachmentData {
     enum AttachmentType {
         case image, video
     }
+    
+    enum Error: Swift.Error {
+        case missingData
+        case export(Swift.Error)
+    }
 }
 
 extension PHAsset {

Tusker/Screens/Compose/ComposeAttachmentRow.swift

@@ -97,7 +97,18 @@ struct ComposeAttachmentRow: View {
         mode = .recognizingText
         
         DispatchQueue.global(qos: .userInitiated).async {
-            self.attachment.data.getData { (data, mimeType) in
+            self.attachment.data.getData { (result) in
+                let data: Data
+                do {
+                    try data = result.get().0
+                } catch {
+                    DispatchQueue.main.async {
+                        self.mode = .allowEntry
+                        self.isShowingTextRecognitionFailedAlert = true
+                        self.textRecognitionErrorMessage = error.localizedDescription
+                    }
+                    return
+                }
                 let handler = VNImageRequestHandler(data: data, options: [:])
                 let request = VNRecognizeTextRequest { (request, error) in
                     DispatchQueue.main.async {

Tusker/Screens/Compose/ComposeView.swift

@@ -244,17 +244,17 @@ struct ComposeView: View {
     private func uploadAttachments(_ completion: @escaping (Result<[Attachment], AttachmentUploadError>) -> Void) {
         let group = DispatchGroup()
         
-        var attachmentDatas = [(Data, String)?]()
+        var attachmentDataResults = [Result<(Data, String), CompositionAttachmentData.Error>?]()
         
         for (index, compAttachment) in draft.attachments.enumerated() {
             group.enter()
             
-            attachmentDatas.append(nil)
+            attachmentDataResults.append(nil)
             
-            compAttachment.data.getData { (data, mimeType) in
+            compAttachment.data.getData { (result) in
                 postProgress += 1
                 
-                attachmentDatas[index] = (data, mimeType)
+                attachmentDataResults[index] = result
                 group.leave()
             }
         }
@@ -271,7 +271,15 @@ struct ComposeView: View {
             // posted status reflects order the user set.
             // Pleroma does respect the order of the `media_ids` parameter.
             
-            for (index, (data, mimeType)) in attachmentDatas.map(\.unsafelyUnwrapped).enumerated() {
+            let datas: [(Data, String)]
+            do {
+                datas = try attachmentDataResults.map { try $0!.get() }
+            } catch {
+                completion(.failure(AttachmentUploadError(errors: [error])))
+                return
+            }
+            
+            for (index, (data, mimeType)) in datas.enumerated() {
                 group.enter()
                 
                 let compAttachment = draft.attachments[index]