Enable formatOnType feature

src/PowerShellEditorServices.Protocol/LanguageServer/ScriptRegionRequest.cs

@@ -0,0 +1,57 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+
+using Microsoft.PowerShell.EditorServices.Protocol.MessageProtocol;
+
+namespace Microsoft.PowerShell.EditorServices.Protocol.LanguageServer
+{
+    /// <summary>
+    /// Class to encapsulate the request type.
+    /// </summary>
+    class ScriptRegionRequest
+    {
+        public static readonly
+            RequestType<ScriptRegionRequestParams, ScriptRegionRequestResult> Type =
+                RequestType<ScriptRegionRequestParams, ScriptRegionRequestResult>.Create("powerShell/getScriptRegion");
+    }
+
+    /// <summary>
+    /// Class to encapsulate the request parameters.
+    /// </summary>
+    class ScriptRegionRequestParams
+    {
+        /// <summary>
+        /// Path of the file for which the formatting region is requested.
+        /// </summary>
+        public string FileUri;
+
+        /// <summary>
+        /// Hint character.
+        /// </summary>
+        public string Character;
+
+        /// <summary>
+        /// 1-based line number of the character.
+        /// </summary>
+        public int Line;
+
+        /// <summary>
+        /// 1-based column number of the character.
+        /// </summary>
+        public int Column;
+    }
+
+    /// <summary>
+    /// Class to encapsulate the result of ScriptRegionRequest.
+    /// </summary>
+    class ScriptRegionRequestResult
+    {
+        /// <summary>
+        /// A region in the script that encapsulates the given character/position which is suitable
+        /// for formatting
+        /// </summary>
+        public ScriptRegion scriptRegion;
+    }
+}

src/PowerShellEditorServices.Protocol/Server/LanguageServer.cs

@@ -125,6 +125,7 @@ protected override void Initialize()
             this.SetRequestHandler(SetPSSARulesRequest.Type, this.HandleSetPSSARulesRequest);
 
             this.SetRequestHandler(ScriptFileMarkersRequest.Type, this.HandleScriptFileMarkersRequest);
+            this.SetRequestHandler(ScriptRegionRequest.Type, this.HandleGetFormatScriptRegionRequest);
 
             this.SetRequestHandler(GetPSHostProcessesRequest.Type, this.HandleGetPSHostProcessesRequest);
 
@@ -235,6 +236,48 @@ await RunScriptDiagnostics(
             await sendresult;
         }
 
+        private async Task HandleGetFormatScriptRegionRequest(
+            ScriptRegionRequestParams requestParams,
+            RequestContext<ScriptRegionRequestResult> requestContext)
+        {
+            var scriptFile = this.editorSession.Workspace.GetFile(requestParams.FileUri);
+            var lineNumber = requestParams.Line;
+            var columnNumber = requestParams.Column;
+            ScriptRegion scriptRegion = null;
+
+            switch (requestParams.Character)
+            {
+                case "\n":
+                    // find the smallest statement ast that occupies
+                    // the element before \n or \r\n and return the extent.
+                    --lineNumber; // vscode sends the next line when pressed enter
+                    var line = scriptFile.GetLine(lineNumber);
+                    if (!String.IsNullOrEmpty(line))
+                    {
+                        scriptRegion = this.editorSession.LanguageService.FindSmallestStatementAstRegion(
+                            scriptFile,
+                            lineNumber,
+                            line.Length);
+                    }
+                    break;
+
+                case "}":
+                    scriptRegion = this.editorSession.LanguageService.FindSmallestStatementAstRegion(
+                            scriptFile,
+                            lineNumber,
+                            columnNumber);
+                    break;
+
+                default:
+                    break;
+            }
+
+            await requestContext.SendResult(new ScriptRegionRequestResult
+            {
+                scriptRegion = scriptRegion
+            });
+        }
+
         private async Task HandleScriptFileMarkersRequest(
             ScriptFileMarkerRequestParams requestParams,
             RequestContext<ScriptFileMarkerRequestResultParams> requestContext)

src/PowerShellEditorServices/Language/LanguageService.cs

@@ -450,6 +450,28 @@ await CommandHelpers.GetCommandInfo(
             }
         }
 
+        /// <summary>
+        /// Gets the smallest statment ast that contains the given script position as
+        /// indicated by lineNumber and columnNumber parameters.
+        /// </summary>
+        /// <param name="scriptFile">Open script file.</param>
+        /// <param name="lineNumber">1-based line number of the position.</param>
+        /// <param name="columnNumber">1-based column number of the position.</param>
+        /// <returns></returns>
+        public ScriptRegion FindSmallestStatementAstRegion(
+            ScriptFile scriptFile,
+            int lineNumber,
+            int columnNumber)
+        {
+            var ast = FindSmallestStatementAst(scriptFile, lineNumber, columnNumber);
+            if (ast == null)
+            {
+                return null;
+            }
+
+            return ScriptRegion.Create(ast.Extent);
+        }
+
         #endregion
 
         #region Private Fields
@@ -569,6 +591,17 @@ private SymbolReference FindDeclarationForBuiltinCommand(
             return foundDefinition;
         }
 
+        private Ast FindSmallestStatementAst(ScriptFile scriptFile, int lineNumber, int columnNumber)
+        {
+            var asts = scriptFile.ScriptAst.FindAll(ast =>
+            {
+                return ast is StatementAst && ast.Extent.Contains(lineNumber, columnNumber);
+            }, true);
+
+            // Find ast with the smallest extent
+            return asts.MinElement((astX, astY) => astX.Extent.ExtentWidthComparer(astY.Extent));
+        }
+
         #endregion
     }
 }

src/PowerShellEditorServices/Utility/Extensions.cs

@@ -4,6 +4,9 @@
 //
 
 using System;
+using System.Linq;
+using System.Collections.Generic;
+using System.Management.Automation.Language;
 
 namespace Microsoft.PowerShell.EditorServices.Utility
 {
@@ -30,5 +33,122 @@ public static string SafeToString(this object obj)
 
             return str;
         }
+
+        /// <summary>
+        /// Get the maximum of the elements from the given enumerable.
+        /// </summary>
+        /// <typeparam name="T">Type of object for which the enumerable is defined.</typeparam>
+        /// <param name="elements">An enumerable object of type T</param>
+        /// <param name="comparer">A comparer for ordering elements of type T. The comparer should handle null values.</param>
+        /// <returns>An object of type T. If the enumerable is empty or has all null elements, then the method returns null.</returns>
+        public static T MaxElement<T>(this IEnumerable<T> elements, Func<T,T,int> comparer) where T:class
+        {
+            if (elements == null)
+            {
+                throw new ArgumentNullException(nameof(elements));
+            }
+
+            if (comparer == null)
+            {
+                throw new ArgumentNullException(nameof(comparer));
+            }
+
+            if (!elements.Any())
+            {
+                return null;
+            }
+
+            var maxElement = elements.First();
+            foreach(var element in elements.Skip(1))
+            {
+                if (element != null && comparer(element, maxElement) > 0)
+                {
+                    maxElement = element;
+                }
+            }
+
+            return maxElement;
+        }
+
+        /// <summary>
+        /// Get the minimum of the elements from the given enumerable.
+        /// </summary>
+        /// <typeparam name="T">Type of object for which the enumerable is defined.</typeparam>
+        /// <param name="elements">An enumerable object of type T</param>
+        /// <param name="comparer">A comparer for ordering elements of type T. The comparer should handle null values.</param>
+        /// <returns>An object of type T. If the enumerable is empty or has all null elements, then the method returns null.</returns>
+        public static T MinElement<T>(this IEnumerable<T> elements, Func<T, T, int> comparer) where T : class
+        {
+            return MaxElement<T>(elements, (elementX, elementY) => -1 * comparer(elementX, elementY));
+        }
+
+        /// <summary>
+        /// Compare extents with respect to their widths.
+        ///
+        /// Width of an extent is defined as the difference between its EndOffset and StartOffest properties.
+        /// </summary>
+        /// <param name="extentX">Extent of type IScriptExtent.</param>
+        /// <param name="extentY">Extent of type IScriptExtent.</param>
+        /// <returns>0 if extentX and extentY are equal in width. 1 if width of extent X is greater than that of extent Y. Otherwise, -1.</returns>
+        public static int ExtentWidthComparer(this IScriptExtent extentX, IScriptExtent extentY)
+        {
+
+            if (extentX == null && extentY == null)
+            {
+                return 0;
+            }
+
+            if (extentX != null && extentY == null)
+            {
+                return 1;
+            }
+
+            if (extentX == null)
+            {
+                return -1;
+            }
+
+            var extentWidthX = extentX.EndOffset - extentX.StartOffset;
+            var extentWidthY = extentY.EndOffset - extentY.StartOffset;
+            if (extentWidthX > extentWidthY)
+            {
+                return 1;
+            }
+            else if (extentWidthX < extentWidthY)
+            {
+                return -1;
+            }
+            else
+            {
+                return 0;
+            }
+        }
+
+        /// <summary>
+        /// Check if the given coordinates are wholly contained in the instance's extent.
+        /// </summary>
+        /// <param name="scriptExtent">Extent of type IScriptExtent.</param>
+        /// <param name="line">1-based line number.</param>
+        /// <param name="column">1-based column number</param>
+        /// <returns>True if the coordinates are wholly contained in the instance's extent, otherwise, false.</returns>
+        public static bool Contains(this IScriptExtent scriptExtent, int line, int column)
+        {
+            if (scriptExtent.StartLineNumber > line || scriptExtent.EndLineNumber < line)
+            {
+                return false;
+            }
+
+            if (scriptExtent.StartLineNumber == line)
+            {
+                return scriptExtent.StartColumnNumber <= column;
+            }
+
+            if (scriptExtent.EndLineNumber == line)
+            {
+                return scriptExtent.EndColumnNumber >= column;
+            }
+
+            return true;
+        }
     }
 }