Improve path auto-completion (PowerShell#902)

* WIP: Improve path auto-completion

* Add comment to address PR feedback

* Address PR feedback

* Add tests for path completion, do not do snippet completion on files

* Fix incorrect macOS/Linxu path in completion test

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
     {
@@ -86,6 +92,8 @@ public class CompletionItem
 
         public string InsertText { get; set; }
 
+        public InsertTextFormat InsertTextFormat { get; set; } = InsertTextFormat.PlainText;
+
         public Range Range { get; set; }
 
         public string[] CommitCharacters { get; set; }

src/PowerShellEditorServices.Protocol/Server/LanguageServer.cs

@@ -1922,6 +1922,8 @@ 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))
@@ -1963,6 +1965,19 @@ private static CompletionItem CreateCompletionItem(
                     }
                 }
             }
+            else if ((completionDetails.CompletionType == CompletionType.Folder) &&
+                     (completionText.EndsWith("\"") || completionText.EndsWith("'")))
+            {
+                // Insert a final "tab stop" as identified by $0 in the snippet provided for completion.
+                // For folder paths, we take the path returned by PowerShell e.g. 'C:\Program Files' and insert
+                // the tab stop marker before the closing quote char e.g. 'C:\Program Files$0'.
+                // This causes the editing cursor to be placed *before* the final quote after completion,
+                // which makes subsequent path completions work. See this part of the LSP spec for details:
+                // https://microsoft.github.io/language-server-protocol/specification#textDocument_completion
+                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
@@ -1973,7 +1988,8 @@ private static CompletionItem CreateCompletionItem(
 
             return new CompletionItem
             {
-                InsertText = completionDetails.CompletionText,
+                InsertText = completionText,
+                InsertTextFormat = insertTextFormat,
                 Label = completionDetails.ListItemText,
                 Kind = MapCompletionKind(completionDetails.CompletionType),
                 Detail = detailString,
@@ -1982,7 +1998,7 @@ private static CompletionItem CreateCompletionItem(
                 FilterText = completionDetails.CompletionText,
                 TextEdit = new TextEdit
                 {
-                    NewText = completionDetails.CompletionText,
+                    NewText = completionText,
                     Range = new Range
                     {
                         Start = new Position

test/PowerShellEditorServices.Test.Host/LanguageServerTests.cs

@@ -15,6 +15,7 @@
 using System;
 using System.IO;
 using System.Linq;
+using System.Runtime.InteropServices;
 using System.Threading.Tasks;
 using Xunit;
 
@@ -260,6 +261,97 @@ await this.SendRequest(
             Assert.True(updatedCompletionItem.Documentation.Length > 0);
         }
 
+        [Fact]
+        public async Task CompletesDetailOnFilePathSuggestion()
+        {
+            string expectedPathSnippet;
+
+            if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
+            {
+                expectedPathSnippet = @".\TestFiles\CompleteFunctionName.ps1";
+            }
+            else
+            {
+                expectedPathSnippet = "./TestFiles/CompleteFunctionName.ps1";
+            }
+
+            // Change dir to root of this test project's folder
+            await this.SetLocationForServerTest(this.TestRootDir);
+
+            await this.SendOpenFileEvent(TestUtilities.NormalizePath("TestFiles/CompleteFunctionName.ps1"));
+
+            CompletionItem[] completions =
+                await this.SendRequest(
+                    CompletionRequest.Type,
+                    new TextDocumentPositionParams
+                    {
+                        TextDocument = new TextDocumentIdentifier
+                        {
+                            Uri = TestUtilities.NormalizePath("TestFiles/CompleteFunctionName.ps1")
+                        },
+                        Position = new Position
+                        {
+                            Line = 8,
+                            Character = 35
+                        }
+                    });
+
+            CompletionItem completionItem =
+                completions
+                    .FirstOrDefault(
+                        c => c.InsertText == expectedPathSnippet);
+
+            Assert.NotNull(completionItem);
+            Assert.Equal(InsertTextFormat.PlainText, completionItem.InsertTextFormat);
+        }
+
+        [Fact]
+        public async Task CompletesDetailOnFolderPathSuggestion()
+        {
+            string expectedPathSnippet;
+            InsertTextFormat insertTextFormat;
+
+            if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
+            {
+                expectedPathSnippet = @"'.\TestFiles\Folder With Spaces$0'";
+                insertTextFormat = InsertTextFormat.Snippet;
+            }
+            else
+            {
+                expectedPathSnippet = @"'./TestFiles/Folder With Spaces$0'";
+                insertTextFormat = InsertTextFormat.Snippet;
+            }
+
+            // Change dir to root of this test project's folder
+            await this.SetLocationForServerTest(this.TestRootDir);
+
+            await this.SendOpenFileEvent(TestUtilities.NormalizePath("TestFiles/CompleteFunctionName.ps1"));
+
+            CompletionItem[] completions =
+                await this.SendRequest(
+                    CompletionRequest.Type,
+                    new TextDocumentPositionParams
+                    {
+                        TextDocument = new TextDocumentIdentifier
+                        {
+                            Uri = TestUtilities.NormalizePath("TestFiles/CompleteFunctionName.ps1")
+                        },
+                        Position = new Position
+                        {
+                            Line = 7,
+                            Character = 32
+                        }
+                    });
+
+            CompletionItem completionItem =
+                completions
+                    .FirstOrDefault(
+                        c => c.InsertText == expectedPathSnippet);
+
+            Assert.NotNull(completionItem);
+            Assert.Equal(insertTextFormat, completionItem.InsertTextFormat);
+        }
+
         [Fact]
         public async Task FindsReferencesOfVariable()
         {
@@ -829,6 +921,27 @@ await this.SendRequest(
             Assert.Equal(expectedArchitecture, versionDetails.Architecture);
         }
 
+        private string TestRootDir
+        {
+            get
+            {
+                string assemblyDir = Path.GetDirectoryName(this.GetType().Assembly.Location);
+                return Path.Combine(assemblyDir, @"..\..\..");
+            }
+        }
+
+        private async Task SetLocationForServerTest(string path)
+        {
+            // Change dir to root of this test project's folder
+            await this.SendRequest(
+                EvaluateRequest.Type,
+                new EvaluateRequestArguments
+                {
+                    Expression = $"Set-Location {path}",
+                    Context = "repl"
+                });
+        }
+
         private async Task SendOpenFileEvent(string filePath, bool waitForDiagnostics = true)
         {
             string fileContents = string.Join(Environment.NewLine, File.ReadAllLines(filePath));

test/PowerShellEditorServices.Test.Host/TestFiles/CompleteFunctionName.ps1

@@ -4,4 +4,6 @@ function My-Function
 $Cons
 My-
 Get-Proc
-$HKC
+$HKC
+Get-ChildItem ./TestFiles/Folder
+Get-ChildItem ./TestFiles/CompleteF