Reinstate loading of local HTML files in WKWebViewRenderer (#12029)

* Allow loading of local HTML files in WKWebViewRenderer; makes test 32033 work again

* Revert whitespace changes

* Add missing using directive

Author: hartez

Xamarin.Forms.Platform.iOS/Renderers/WkWebViewRenderer.cs

@@ -3,6 +3,7 @@
 using System.ComponentModel;
 using System.Diagnostics;
 using System.Drawing;
+using System.IO;
 using System.Linq;
 using System.Net;
 using System.Text;
@@ -104,17 +105,55 @@ public async void LoadUrl(string url)
 			try
 			{
 				var uri = new Uri(url);
+
 				var safeHostUri = new Uri($"{uri.Scheme}://{uri.Authority}", UriKind.Absolute);
 				var safeRelativeUri = new Uri($"{uri.PathAndQuery}{uri.Fragment}", UriKind.Relative);
 				NSUrlRequest request = new NSUrlRequest(new Uri(safeHostUri, safeRelativeUri));
 
 				await SyncNativeCookies(url);
 				LoadRequest(request);
 			}
+			catch (UriFormatException formatException)
+			{
+				// If we got a format exception trying to parse the URI, it might be because
+				// someone is passing in a local bundled file page. If we can find a better way
+				// to detect that scenario, we should use it; until then, we'll fall back to 
+				// local file loading here and see if that works:
+				if (!LoadFile(url))
+				{
+					Log.Warning(nameof(WkWebViewRenderer), $"Unable to Load Url {url}: {formatException}");
+				}
+			}
 			catch (Exception exc)
 			{
-				Log.Warning(nameof(WkWebViewRenderer), $"Unable to Load Url {exc}");
+				Log.Warning(nameof(WkWebViewRenderer), $"Unable to Load Url {url}: {exc}");
+			}
+		}
+
+		bool LoadFile(string url)
+		{
+			try
+			{
+				var file = Path.GetFileNameWithoutExtension(url);
+				var ext = Path.GetExtension(url);
+
+				var nsUrl = NSBundle.MainBundle.GetUrlForResource(file, ext);
+
+				if (nsUrl == null)
+				{
+					return false;
+				}
+
+				LoadFileUrl(nsUrl, nsUrl);
+
+				return true;
+			}
+			catch (Exception ex)
+			{
+				Log.Warning(nameof(WkWebViewRenderer), $"Could not load {url} as local file: {ex}");
 			}
+
+			return false;
 		}
 
 		public override void LayoutSubviews()