Ensure completionapi experiment does not interfere with integration tests

src/VisualStudio/IntegrationTest/TestUtilities/VisualStudioInstanceFactory.cs

@@ -11,6 +11,7 @@
 using System.Threading.Tasks;
 using EnvDTE;
 using Microsoft.VisualStudio.Setup.Configuration;
+using Microsoft.Win32;
 using RunTests;
 using Process = System.Diagnostics.Process;
 
@@ -327,6 +328,15 @@ private static Process StartNewVisualStudioProcess(string installationPath, int
                 // Disable background download UI to avoid toasts
                 Process.Start(vsRegEditExeFile, $"set \"{installationPath}\" {Settings.Default.VsRootSuffix} HKCU \"FeatureFlags\\Setup\\BackgroundDownload\" Value dword 0").WaitForExit();
 
+                // Remove legacy experiment setting for controlling async completion to ensure it does not interfere.
+                // We no longer set this value, but it could be in place from an earlier test run on the same machine.
+                var disabledFlights = Registry.GetValue(@"HKEY_CURRENT_USER\Software\Microsoft\VisualStudio\ABExp\LocalTest", "DisabledFlights", Array.Empty<string>()) as string[] ?? Array.Empty<string>();
+                if (disabledFlights.Any(flight => string.Equals(flight, "completionapi", StringComparison.OrdinalIgnoreCase)))
+                {
+                    disabledFlights = disabledFlights.Where(flight => !string.Equals(flight, "completionapi", StringComparison.OrdinalIgnoreCase)).ToArray();
+                    Registry.SetValue(@"HKEY_CURRENT_USER\Software\Microsoft\VisualStudio\ABExp\LocalTest", "DisabledFlights", disabledFlights, RegistryValueKind.MultiString);
+                }
+
                 // Disable text editor error reporting because it pops up a dialog. We want to either fail fast in our
                 // custom handler or fail silently and continue testing.
                 Process.Start(vsRegEditExeFile, $"set \"{installationPath}\" {Settings.Default.VsRootSuffix} HKCU \"Text Editor\" \"Report Exceptions\" dword 0").WaitForExit();