Fix bug where bg of -1 causes crash of interactive session.

Fix bug where the user can select the bottom most stack frame during interactive session debugging and that generates an error in VSCode when it can't find <No File>.
Fix PowerShell#555 ParameterBindingValidationException when invoking PSSA on an empty PS1 file.

Author: rkeithhill

src/PowerShellEditorServices.Protocol/DebugAdapter/StackFrame.cs

@@ -61,19 +61,28 @@ public static StackFrame Create(
             var sourcePresentationHint = 
                 stackFrame.IsExternalCode ? SourcePresentationHint.Deemphasize : SourcePresentationHint.Normal;
 
+            // When debugging an interactive session, the ScriptPath is <No File> which is not a valid source file.
+            // We need to make sure the user can't open the file associated with this stack frame.
+            // It will generate a VSCode error in this case.
+            Source source = null;
+            if (!stackFrame.ScriptPath.Contains("<"))
+            {
+                source = new Source
+                {
+                    Path = stackFrame.ScriptPath,
+                    PresentationHint = sourcePresentationHint.ToString().ToLower()
+                };
+            }
+
             return new StackFrame
             {
                 Id = id,
-                Name = stackFrame.FunctionName,
-                Line = stackFrame.StartLineNumber,
+                Name = (source != null) ? stackFrame.FunctionName : "Interactive Session",
+                Line = (source != null) ? stackFrame.StartLineNumber : 0,
                 EndLine = stackFrame.EndLineNumber,
-                Column = stackFrame.StartColumnNumber,
+                Column = (source != null) ? stackFrame.StartColumnNumber : 0,
                 EndColumn = stackFrame.EndColumnNumber,
-                Source = new Source
-                {
-                    Path = stackFrame.ScriptPath,
-                    PresentationHint = sourcePresentationHint.ToString().ToLower()
-                }
+                Source = source
             };
         }
     }

src/PowerShellEditorServices.Protocol/Server/DebugAdapter.cs

@@ -86,7 +86,7 @@ protected Task LaunchScript(RequestContext<object> requestContext)
             // Is this an untitled script?
             Task launchTask = null;
 
-            if (this.scriptToLaunch.StartsWith("untitled"))
+            if (this.scriptToLaunch.StartsWith("untitled:"))
             {
                 ScriptFile untitledScript =
                     this.editorSession.Workspace.GetFile(
@@ -253,6 +253,12 @@ protected async Task HandleLaunchRequest(
                 launchParams.Program;
 #pragma warning restore 618
 
+            // We come through here first when debugging an untitled (unsaved) file - there is now working dir.
+            if (workingDir.StartsWith("untitled:"))
+            {
+                workingDir = null;
+            }
+
             if (workingDir != null)
             {
                 workingDir = PowerShellContext.UnescapePath(workingDir);

src/PowerShellEditorServices/Analysis/AnalysisService.cs

@@ -413,6 +413,14 @@ private async Task<PSObject[]> GetDiagnosticRecordsAsync<TSettings>(
         {
             var diagnosticRecords = new PSObject[0];
 
+            // When a new, empty file is created there are by definition no issues.
+            // Furthermore, if you call Invoke-ScriptAnalyzer with an empty ScriptDefinition
+            // it will generate a ParameterBindingValidationException.
+            if (string.IsNullOrEmpty(scriptContent))
+            {
+                return diagnosticRecords;
+            }
+
             if (hasScriptAnalyzerModule
                 && (typeof(TSettings) == typeof(string)
                     || typeof(TSettings) == typeof(Hashtable)))

src/PowerShellEditorServices/Session/Host/TerminalPSHostUserInterface.cs

@@ -131,7 +131,7 @@ public override void WriteOutput(
             ConsoleColor oldBackgroundColor = System.Console.BackgroundColor;
 
             System.Console.ForegroundColor = foregroundColor;
-            System.Console.BackgroundColor = backgroundColor;
+            System.Console.BackgroundColor = ((int)backgroundColor != -1) ? backgroundColor : oldBackgroundColor;
 
             System.Console.Write(outputString + (includeNewLine ? Environment.NewLine : ""));