Enable PowerShell script debugger

src/Microsoft.PowerShell.Linux.Host/main.cs

@@ -122,6 +122,11 @@ namespace Microsoft.PowerShell.Linux.Host
         /// </summary>
         private object instanceLock = new object();
 
+        /// <summary>
+        /// To keep track whether we've displayed the debugger help message
+        /// </summary>
+        private bool _showHelpMessage;
+
         /// <summary>
         /// Gets or sets a value indicating whether the host application
         /// should exit.
@@ -152,6 +157,17 @@ namespace Microsoft.PowerShell.Linux.Host
             this.myRunSpace = RunspaceFactory.CreateRunspace(this.myHost, iss);
             this.myRunSpace.Open();
 
+            if (this.myRunSpace.Debugger != null)
+            {
+                this.myRunSpace.Debugger.DebuggerStop += HandleDebuggerStopEvent;
+
+                // Workflow debugging is new for PowerShell version 4 and is an opt-in
+                // feature.  In order to debug Workflow script functions the debugger
+                // DebugMode must include the DebugModes.LocalScript flag.
+                this.myRunSpace.Debugger.SetDebugMode(DebugModes.LocalScript);
+
+            }
+
             // Create a PowerShell object to run the commands used to create
             // $profile and load the profiles.
             lock (this.instanceLock)
@@ -447,5 +463,96 @@ namespace Microsoft.PowerShell.Linux.Host
             // The exit code is set in the host by the MyHost.SetShouldExit() method.
             //Environment.Exit(this.ExitCode);
         }
+
+        /// <summary>
+        /// Method to handle the Debugger DebuggerStop event.
+        /// </summary>
+        /// <param name="sender"> Debugger instance
+        /// <param name="args"> DebuggerStop event args
+        private void HandleDebuggerStopEvent(object sender, DebuggerStopEventArgs args)
+        {
+            Debugger debugger = sender as Debugger;
+            DebuggerResumeAction? resumeAction = null;
+
+            WriteDebuggerStopMessages(args);
+
+            // loop to process Debugger commands.
+            while (resumeAction == null)
+            {
+                Console.Write("[DBG] PS >> ");
+                string command = Console.ReadLine();
+                Console.WriteLine();
+
+                // Stream output from command processing to console.
+                var output = new PSDataCollection<PSObject>();
+                output.DataAdded += (dSender, dArgs) =>
+                {
+                    foreach (var item in output.ReadAll())
+                    {
+                        Console.WriteLine(item);
+                    }
+                };
+
+                // Process command.
+                // The Debugger.ProcesCommand method will parse and handle debugger specific
+                // commands such as 'h' (help), 'list', 'stepover', etc.  If the command is
+                // not specific to the debugger then it will be evaluated as a PowerShell
+                // command or script.  The returned DebuggerCommandResults object will indicate
+                // whether the command was evaluated by the debugger and if the debugger should
+                // be released with a specific resume action.
+                PSCommand psCommand = new PSCommand();
+                psCommand.AddScript(command).AddCommand("Out-String").AddParameter("Stream", true);
+                DebuggerCommandResults results = debugger.ProcessCommand(psCommand, output);
+                if (results.ResumeAction != null)
+                {
+                    resumeAction = results.ResumeAction;
+                }
+            }
+
+            // Return from event handler with user resume action.
+            args.ResumeAction = resumeAction.Value;
+        }
+
+        /// <summary>
+        /// Helper method to write debugger stop messages.
+        /// </summary>
+        /// <param name="args">DebuggerStopEventArgs for current debugger stop</param>
+        private void WriteDebuggerStopMessages(DebuggerStopEventArgs args)
+        {
+            // Write debugger stop information in yellow.
+            ConsoleColor saveFGColor = Console.ForegroundColor;
+            Console.ForegroundColor = ConsoleColor.Yellow;
+
+            // Show help message only once.
+            if (!_showHelpMessage)
+            {
+                Console.WriteLine("Entering debug mode. Type 'h' to get help.");
+                Console.WriteLine();
+                _showHelpMessage = true;
+            }
+
+            // Breakpoint stop information.  Writes all breakpoints that
+            // pertain to this debugger execution stop point.
+            if (args.Breakpoints.Count > 0)
+            {
+                Console.WriteLine("Debugger hit breakpoint on:");
+                foreach (var breakPoint in args.Breakpoints)
+                {
+                    Console.WriteLine(breakPoint.ToString());
+                }
+                Console.WriteLine();
+            }
+
+            // Script position stop information.
+            // This writes the InvocationInfo position message if
+            // there is one.
+            if (args.InvocationInfo != null)
+            {
+                Console.WriteLine(args.InvocationInfo.PositionMessage);
+                Console.WriteLine();
+            }
+
+            Console.ForegroundColor = saveFGColor;
+        }
     }
 }