Recognize debugger pseudo-commands

ValidateAndAcceptLine was rejecting debugger commands like 's' or 'k'.
Now we check if we are debugging and accept these fake commands.

Fixes #199

Author: lzybkr

PSReadLine/BasicEditing.cs

@@ -370,6 +370,28 @@ private bool UnresolvedCommandCouldSucceed(string commandName, Ast rootAst)
                 }
             }
 
+            if (commandName.Length == 1)
+            {
+                switch (commandName[0])
+                {
+                // The following are debugger commands that should be accepted if we're debugging
+                // because the console host will interpret these commands directly.
+                case 's': case 'v': case 'o': case 'c': case 'q': case'k': case 'l':
+                case 'S': case 'V': case 'O': case 'C': case 'Q': case'K': case 'L':
+                case '?': case 'h': case 'H':
+                    // Ideally we would check $PSDebugContext, but it is set at function
+                    // scope, and because we're in a module, we can't find that variable
+                    // (arguably a PowerShell issue.)
+                    // NestedPromptLevel is good enough though - it's rare to be in a nested.
+                    var nestedPromptLevel = _engineIntrinsics.SessionState.PSVariable.GetValue("NestedPromptLevel");
+                    if (nestedPromptLevel is int)
+                    {
+                        return ((int)nestedPromptLevel) > 0;
+                    }
+                    break;
+                }
+            }
+
             return false;
         }