 import Articles
 import RSCore
 import Account
+
+public enum SidebarOutlineDataSourceError: LocalizedError {
+	case createErrorNotFound([String])
+	
+	public var errorDescription: String? {
+		switch self {
+		case .createErrorNotFound(let feedNames):
+			let message = NSLocalizedString("The following feeds could not be added because they could not be found:\n", comment: "Not found")
+			return "\(message)\(feedNames.joined(separator: ", "))"
+		}
+	}
+}
 
 @objc final class SidebarOutlineDataSource: NSObject, NSOutlineViewDataSource {
 

							case .success:
								break
							case .failure(let error):
								NSApplication.shared.presentError(error)
							}
						}
					}
				}
				group.notify(queue: DispatchQueue.main) {
					completion()
				}
			case .failure(let error):
				NSApplication.shared.presentError(error)

			switch result {
			case .success(let destinationFolder):
				let group = DispatchGroup()
				var notFoundFeedNames = [String]()
				for feed in folder.topLevelWebFeeds {
					if let existingFeed = destinationAccount.existingWebFeed(withURL: feed.url) {
						group.enter()
