Avoid writing out the temporary file if it's already there

If the file is already open, then this was causing us to trigger a
reload prompt which we don't want.

src/VisualStudio/Core/Def/Implementation/Workspace/SourceGeneratedFileManager.cs

@@ -99,7 +99,12 @@ public void NavigateToSourceGeneratedFile(Project project, ISourceGenerator gene
             // The file name we generate here is chosen to match the compiler's choice, so the debugger can recognize the files should match.
             // This can only be changed if the compiler changes the algorithm as well.
             var temporaryFilePath = Path.Combine(projectDirectory, $"{generatorType.Module.ModuleVersionId}_{generatorType.FullName}_{generatedSourceHintName}");
-            File.WriteAllText(temporaryFilePath, "");
+
+            // Don't write to the file if it's already there, as that potentially triggers a file reload
+            if (!File.Exists(temporaryFilePath))
+            {
+                File.WriteAllText(temporaryFilePath, "");
+            }
 
             var openDocumentService = _serviceProvider.GetService<SVsUIShellOpenDocument, IVsUIShellOpenDocument>();
             var hr = openDocumentService.OpenDocumentViaProject(