WIP: Improve path auto-completion

Author: rkeithhill

src/PowerShellEditorServices.Protocol/LanguageServer/Completion.cs

@@ -58,6 +58,12 @@ public enum CompletionItemKind
         Folder = 19
     }
 
+    public enum InsertTextFormat
+    {
+        PlainText = 1,
+        Snippet = 2,
+    }
+
     [DebuggerDisplay("NewText = {NewText}, Range = {Range.Start.Line}:{Range.Start.Character} - {Range.End.Line}:{Range.End.Character}")]
     public class TextEdit
     {
@@ -69,6 +75,11 @@ public class TextEdit
     [DebuggerDisplay("Kind = {Kind.ToString()}, Label = {Label}, Detail = {Detail}")]
     public class CompletionItem
     {
+        public CompletionItem()
+        {
+            this.InsertTextFormat = InsertTextFormat.PlainText;
+        }
+
         public string Label { get; set; }
 
         public CompletionItemKind? Kind { get; set; }
@@ -86,6 +97,8 @@ public class CompletionItem
 
         public string InsertText { get; set; }
 
+        public InsertTextFormat InsertTextFormat { get; set; }
+
         public Range Range { get; set; }
 
         public string[] CommitCharacters { get; set; }

src/PowerShellEditorServices.Protocol/Server/LanguageServer.cs

@@ -1915,6 +1915,8 @@ private static CompletionItem CreateCompletionItem(
         {
             string detailString = null;
             string documentationString = null;
+            string completionText = completionDetails.CompletionText;
+            InsertTextFormat insertTextFormat = InsertTextFormat.PlainText;
 
             if ((completionDetails.CompletionType == CompletionType.Variable) ||
                 (completionDetails.CompletionType == CompletionType.ParameterName))
@@ -1956,6 +1958,14 @@ private static CompletionItem CreateCompletionItem(
                     }
                 }
             }
+            else if (((completionDetails.CompletionType == CompletionType.File) ||
+                      (completionDetails.CompletionType == CompletionType.Folder)) &&
+                     (completionText.EndsWith("\"") || completionText.EndsWith("'")))
+            {
+                int len = completionDetails.CompletionText.Length;
+                completionText = completionDetails.CompletionText.Insert(len - 1, "$0");
+                insertTextFormat = InsertTextFormat.Snippet;
+            }
 
             // Force the client to maintain the sort order in which the
             // original completion results were returned. We just need to
@@ -1966,7 +1976,8 @@ private static CompletionItem CreateCompletionItem(
 
             return new CompletionItem
             {
-                InsertText = completionDetails.CompletionText,
+                InsertText = completionText,
+                InsertTextFormat = insertTextFormat,
                 Label = completionDetails.ListItemText,
                 Kind = MapCompletionKind(completionDetails.CompletionType),
                 Detail = detailString,
@@ -1975,7 +1986,7 @@ private static CompletionItem CreateCompletionItem(
                 FilterText = completionDetails.CompletionText,
                 TextEdit = new TextEdit
                 {
-                    NewText = completionDetails.CompletionText,
+                    NewText = completionText,
                     Range = new Range
                     {
                         Start = new Position