Handle cancellation errors.

#301 (comment)

Author: CalebRas

Shared/Samples/Download vector tiles to local cache/DownloadVectorTilesToLocalCacheView.swift

@@ -112,8 +112,6 @@ struct DownloadVectorTilesToLocalCacheView: View {
                                     isShowingResults = true
                                     // Sets downloading to false when the download finishes.
                                     isDownloading = false
-                                } catch is CancellationError {
-                                    // Does nothing if the error is a cancellation error.
                                 } catch {
                                     // Shows an alert if any errors occur.
                                     self.error = error

Shared/Samples/Generate offline map/GenerateOfflineMapView.swift

@@ -216,8 +216,6 @@ private extension GenerateOfflineMapView {
                 offlineMap = output.offlineMap
                 // Sets the initial viewpoint of the offline map.
                 offlineMap.initialViewpoint = Viewpoint(boundingGeometry: extent.expanded(by: 0.8))
-            } catch is CancellationError {
-                // Does nothing if the error is a cancellation error.
             } catch {
                 // Shows an alert with the error if the job fails.
                 self.error = error

Shared/Samples/Identify raster cell/IdentifyRasterCellView.swift

@@ -108,9 +108,6 @@ private extension IdentifyRasterCellView {
                 // Get the first raster cell from the identify result.
                 let rasterCell = identifyResult.geoElements.first(where: { $0 is RasterCell })
                 return rasterCell as? RasterCell
-            } catch is CancellationError {
-                // Does nothing if the error is a cancellation error.
-                return nil
             } catch {
                 self.error = error
                 return nil

Shared/Supporting Files/Extensions/View+ErrorAlert.swift

@@ -17,9 +17,19 @@ import SwiftUI
 extension View {
     /// Presents an alert with a given error's `localizedDescription` as the message.
     /// - Parameter error: A binding to an optional `Error` that will present the alert when
-    /// it is not `nil`. When the user taps "OK", this value is set to `nil` and the alert is dismissed.
+    /// it is not `nil`. When the user taps "OK", this value is set to `nil`, and the alert is dismissed.
+    ///
+    /// If the given `error` is a `CancellationError`, it is ignored, and the alert is not presented.
     func errorAlert(presentingError error: Binding<Error?>) -> some View {
-        alert("Error", isPresented: .constant(error.wrappedValue != nil), presenting: error.wrappedValue) { _ in
+        /// A binding to a Boolean value indicating whether to present the alert.
+        let isPresented: Binding<Bool>
+        if error.wrappedValue != nil && !(error.wrappedValue is CancellationError) {
+            isPresented = .constant(true)
+        } else {
+            isPresented = .constant(false)
+        }
+        
+        return alert("Error", isPresented: isPresented, presenting: error.wrappedValue) { _ in
             Button("OK") {
                 error.wrappedValue = nil
             }