Hook up legacy readline support in the host

Author: rjmholt

src/PowerShellEditorServices/Services/PowerShell/Console/LegacyReadLine.cs

@@ -20,20 +20,16 @@ internal class LegacyReadLine : TerminalReadLine
     {
         private readonly PsesInternalHost _psesHost;
 
-        private readonly IPowerShellDebugContext _debugContext;
-
         private readonly Task[] _readKeyTasks;
 
         private Func<bool, ConsoleKeyInfo> _readKeyFunc;
 
         private Action _onIdleAction;
 
         public LegacyReadLine(
-            PsesInternalHost psesHost,
-            IPowerShellDebugContext debugContext)
+            PsesInternalHost psesHost)
         {
             _psesHost = psesHost;
-            _debugContext = debugContext;
             _readKeyTasks = new Task[2];
         }
 
@@ -86,7 +82,7 @@ public override string ReadLine(CancellationToken cancellationToken)
 
                                 // TODO: This logic should be moved to AstOperations or similar!
 
-                                if (_debugContext.IsStopped)
+                                if (_psesHost.DebugContext.IsStopped)
                                 {
                                     PSCommand command = new PSCommand()
                                         .AddCommand("TabExpansion2")

src/PowerShellEditorServices/Services/PowerShell/Host/PsesInternalHost.cs

@@ -625,10 +625,14 @@ private static PowerShell CreatePowerShellForRunspace(Runspace runspace)
 
             var engineIntrinsics = (EngineIntrinsics)runspace.SessionStateProxy.GetVariable("ExecutionContext");
 
-            if (hostStartupInfo.ConsoleReplEnabled && !hostStartupInfo.UsesLegacyReadLine)
+            if (hostStartupInfo.ConsoleReplEnabled)
             {
-                var psrlProxy = PSReadLineProxy.LoadAndCreate(_loggerFactory, pwsh);
-                var readLine = new PsrlReadLine(psrlProxy, this, engineIntrinsics);
+                // If we've been configured to use it, or if we can't load PSReadLine, use the legacy readline
+                if (hostStartupInfo.UsesLegacyReadLine || !TryLoadPSReadLine(pwsh, engineIntrinsics, out IReadLine readLine))
+                {
+                    readLine = new LegacyReadLine(this);
+                }
+
                 readLine.TryOverrideReadKey(ReadKey);
                 readLine.TryOverrideIdleHandler(OnPowerShellIdle);
                 readLineProvider.OverrideReadLine(readLine);
@@ -823,6 +827,22 @@ private Task PopOrReinitializeRunspaceAsync()
                 CancellationToken.None);
         }
 
+        private bool TryLoadPSReadLine(PowerShell pwsh, EngineIntrinsics engineIntrinsics, out IReadLine psrlReadLine)
+        {
+            psrlReadLine = null;
+            try
+            {
+                var psrlProxy = PSReadLineProxy.LoadAndCreate(_loggerFactory, pwsh);
+                psrlReadLine = new PsrlReadLine(psrlProxy, this, engineIntrinsics);
+                return true;
+            }
+            catch (Exception e)
+            {
+                _logger.LogError(e, "Unable to load PSReadLine. Will fall back to legacy readline implementation.");
+                return false;
+            }
+        }
+
         private record RunspaceFrame(
             Runspace Runspace,
             RunspaceInfo RunspaceInfo);