Convert symbol-search crash to NFW

src/Features/Core/Portable/SymbolSearch/Windows/SymbolSearchUpdateEngine.Update.cs

@@ -511,23 +511,22 @@ private async Task<XElement> DownloadFileAsync(string serverPath, CancellationTo
                 {
                     cancellationToken.ThrowIfCancellationRequested();
 
-                    var resultOpt = await TryDownloadFileAsync(client, cancellationToken).ConfigureAwait(false);
-                    if (resultOpt == null)
+                    var (element, delay) = await TryDownloadFileAsync(client, cancellationToken).ConfigureAwait(false);
+                    if (element == null)
                     {
-                        var delay = _service._delayService.CachePollDelay;
                         await LogInfoAsync($"File not downloaded. Trying again in {delay}", cancellationToken).ConfigureAwait(false);
                         await Task.Delay(delay, cancellationToken).ConfigureAwait(false);
                     }
                     else
                     {
                         // File was downloaded.  
-                        return resultOpt;
+                        return element;
                     }
                 }
             }
 
             /// <summary>Returns 'null' if download is not available and caller should keep polling.</summary>
-            private async Task<XElement> TryDownloadFileAsync(IFileDownloader fileDownloader, CancellationToken cancellationToken)
+            private async Task<(XElement element, TimeSpan delay)> TryDownloadFileAsync(IFileDownloader fileDownloader, CancellationToken cancellationToken)
             {
                 await LogInfoAsync("Read file from client", cancellationToken).ConfigureAwait(false);
 
@@ -536,7 +535,7 @@ private async Task<XElement> TryDownloadFileAsync(IFileDownloader fileDownloader
                 if (stream == null)
                 {
                     await LogInfoAsync("Read file completed. Client returned no data", cancellationToken).ConfigureAwait(false);
-                    return null;
+                    return (element: null, _service._delayService.CachePollDelay);
                 }
 
                 await LogInfoAsync("Read file completed. Client returned data", cancellationToken).ConfigureAwait(false);
@@ -554,28 +553,23 @@ private async Task<XElement> TryDownloadFileAsync(IFileDownloader fileDownloader
 
                 // This code must always succeed.  If it does not, that means that either the server reported bogus data
                 // to the file-downloader, or the file-downloader is serving us bogus data.  In other event, there is
-                // something wrong with those components, and we should both report the issue to watson, and stop doing
+                // something wrong with those components, and we should both report the issue to Watson, and stop doing
                 // the update.
                 try
                 {
                     using var reader = XmlReader.Create(stream, settings);
 
-                    var result = XElement.Load(reader);
+                    var element = XElement.Load(reader);
                     await LogInfoAsync("Converting data to XElement completed", cancellationToken).ConfigureAwait(false);
-                    return result;
-                }
-                catch (Exception e) when (ReportAndDoNotCatch(e))
-                {
-                    throw ExceptionUtilities.Unreachable();
+                    return (element, delay: default);
                 }
-
-                bool ReportAndDoNotCatch(Exception exception)
+                catch (Exception e) when (_service._reportAndSwallowExceptionUnlessCanceled(e, cancellationToken))
                 {
-                    // Directly report issue here so we can collect a dump that indicates precisely what is in the
-                    // stream. Then return 'false' explicitly so that the catch handler doesn't run and the exception
-                    // properly tears down the update.
-                    _service._reportAndSwallowExceptionUnlessCanceled(exception, cancellationToken);
-                    return false;
+                    // We retrieved bytes from the server, but we couldn't make parse it an xml. out of it.  That's very
+                    // bad.  Just trying again one minute later isn't going to help.  We need to wait until there is
+                    // good data on the server for us to download.
+                    await LogInfoAsync($"Unable to parse file as XElement", cancellationToken).ConfigureAwait(false);
+                    return (element: null, _service._delayService.CatastrophicFailureDelay);
                 }
             }