Implicit Revert Row Cleanup Logic (#297)

This change enhances the way that edit/updateCell and edit/revertCell operations are performed. 

## **THE API BREAKING CHANGES**:
* edit/updateCell now returns an EditCell (a DbCellValue with a dirty flag) and a row dirty flag.
* edit/revertCell now returns an EditCell (a DbCellValue with a dirty flag) and a row dirty flag.

If by setting the value of a cell via edit/updateCell the row no longer has any edits (an "implicit revert"), the entire row's edit will be removed from the cache. Additionally, if by requesting edit/revert all the pending edits for a row are removed, the entire row's edit will be removed from the cache. This will prevent issues where committing will generate an invalid script because it has no pending changes.

* Adding EditCell class
Returning EditCell with EditUpdateCellResult

* Adding code that will remove a row update if the row is clean after a cell update

* Adding code that will return an EditCell and row dirty flag when a cell is reverted.
If the row is reverted by the cell revert, the pending update will be removed

* Comments for edit cell

* Changes as per pull request comments

src/Microsoft.SqlTools.ServiceLayer/EditData/Contracts/EditCell.cs

@@ -0,0 +1,39 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+
+using Microsoft.SqlTools.ServiceLayer.QueryExecution.Contracts;
+
+namespace Microsoft.SqlTools.ServiceLayer.EditData.Contracts
+{
+    /// <summary>
+    /// Cell that wraps info from <see cref="DbCellValue"/> for edit purposes
+    /// </summary>
+    public class EditCell : DbCellValue
+    {
+        /// <summary>
+        /// Default, parameterless constructor to make sure that JSON serializing is happy
+        /// </summary>
+        public EditCell() {}
+
+        /// <summary>
+        /// Constructs a new EditCell based on a DbCellValue
+        /// </summary>
+        /// <param name="dbCellValue">The DbCellValue that will be enhanced</param>
+        /// <param name="isDirty">Whether or not the edit cell is dirty</param>
+        public EditCell(DbCellValue dbCellValue, bool isDirty)
+        {
+            IsDirty = isDirty;
+
+            DisplayValue = dbCellValue.DisplayValue;
+            IsNull = dbCellValue.IsNull;
+            RawObject = dbCellValue.RawObject;
+        }
+
+        /// <summary>
+        /// Whether or not the cell is considered dirty
+        /// </summary>
+        public bool IsDirty { get; set; }
+    }
+}

src/Microsoft.SqlTools.ServiceLayer/EditData/Contracts/EditCellResult.cs

@@ -0,0 +1,18 @@
+namespace Microsoft.SqlTools.ServiceLayer.EditData.Contracts
+{
+    /// <summary>
+    /// Parameters to return when a cell is updated in isolation
+    /// </summary>
+    public class EditCellResult
+    {
+        /// <summary>
+        /// The cell after the revert was applied
+        /// </summary>
+        public EditCell Cell { get; set; }
+
+        /// <summary>
+        /// Whether or not the row is dirty after the revert has been applied
+        /// </summary>
+        public bool IsRowDirty { get; set; }
+    }
+}

src/Microsoft.SqlTools.ServiceLayer/EditData/Contracts/EditRevertCellRequest.cs

@@ -7,14 +7,19 @@ using Microsoft.SqlTools.Hosting.Protocol.Contracts;
 
 namespace Microsoft.SqlTools.ServiceLayer.EditData.Contracts
 {
+    /// <summary>
+    /// Parameters for the cell revert request
+    /// </summary>
     public class EditRevertCellParams : RowOperationParams
     {
         public int ColumnId { get; set; }
     }
 
-    public class EditRevertCellResult
+    /// <summary>
+    /// Parameters to return upon successful revert of the cell
+    /// </summary>
+    public class EditRevertCellResult : EditCellResult
     {
-        public string NewValue { get; set; }
     }
 
     public class EditRevertCellRequest

src/Microsoft.SqlTools.ServiceLayer/EditData/Contracts/EditUpdateCellRequest.cs

@@ -26,31 +26,8 @@ namespace Microsoft.SqlTools.ServiceLayer.EditData.Contracts
     /// <summary>
     /// Parameters to return upon successful update of the cell
     /// </summary>
-    public class EditUpdateCellResult
+    public class EditUpdateCellResult : EditCellResult
     {
-        /// <summary>
-        /// Whether or not the cell value was modified from the provided string.
-        /// If <c>true</c>, the client should replace the display value of the cell with the value
-        /// in <see cref="NewValue"/>
-        /// </summary>
-        public bool HasCorrections { get; set; }
-
-        /// <summary>
-        /// Whether or not the cell was reverted with the change.
-        /// If <c>true</c>, the client should unmark the cell as having an update and replace the
-        /// display value of the cell with the value in <see cref="NewValue"/>
-        /// </summary>
-        public bool IsRevert { get; set; }
-
-        /// <summary>
-        /// Whether or not the new value of the cell is null
-        /// </summary>
-        public bool IsNull { get; set; }
-
-        /// <summary>
-        /// The new string value of the cell
-        /// </summary>
-        public string NewValue { get; set; }
     }
 
     public class EditUpdateCellRequest

src/Microsoft.SqlTools.ServiceLayer/EditData/EditDataService.cs

@@ -184,14 +184,8 @@ namespace Microsoft.SqlTools.ServiceLayer.EditData
         internal Task HandleRevertCellRequest(EditRevertCellParams revertParams,
             RequestContext<EditRevertCellResult> requestContext)
         {
-            return HandleSessionRequest(revertParams, requestContext, session =>
-            {
-                string newValue = session.RevertCell(revertParams.RowId, revertParams.ColumnId);
-                return new EditRevertCellResult
-                {
-                    NewValue = newValue
-                };
-            });
+            return HandleSessionRequest(revertParams, requestContext,
+                session => session.RevertCell(revertParams.RowId, revertParams.ColumnId));
         }
 
         internal Task HandleRevertRowRequest(EditRevertRowParams revertParams,

src/Microsoft.SqlTools.ServiceLayer/EditData/EditSession.cs

@@ -308,7 +308,7 @@ namespace Microsoft.SqlTools.ServiceLayer.EditData
         /// <param name="rowId">Internal ID of the row to have its edits reverted</param>
         /// <param name="columnId">Ordinal ID of the column to revert</param>
         /// <returns>String version of the old value for the cell</returns>
-        public string RevertCell(long rowId, int columnId)
+        public EditRevertCellResult RevertCell(long rowId, int columnId)
         {
             ThrowIfNotInitialized();
 
@@ -319,8 +319,12 @@ namespace Microsoft.SqlTools.ServiceLayer.EditData
                 throw new ArgumentOutOfRangeException(nameof(rowId), SR.EditDataUpdateNotPending);
             }
 
+            // Update the row
+            EditRevertCellResult revertResult = pendingEdit.RevertCell(columnId);
+            CleanupEditIfRowClean(rowId, revertResult);
+
             // Have the edit base revert the cell
-            return pendingEdit.RevertCell(columnId);
+            return revertResult;
         }
 
         /// <summary>
@@ -410,8 +414,11 @@ namespace Microsoft.SqlTools.ServiceLayer.EditData
             // doesn't already exist in the cache
             RowEditBase editRow = EditCache.GetOrAdd(rowId, key => new RowUpdate(rowId, associatedResultSet, objectMetadata));
 
-            // Pass the call to the row update
-            return editRow.SetCell(columnId, newValue);
+            // Update the row
+            EditUpdateCellResult result = editRow.SetCell(columnId, newValue);
+            CleanupEditIfRowClean(rowId, result);
+
+            return result;
         }
 
         #endregion
@@ -521,6 +528,24 @@ namespace Microsoft.SqlTools.ServiceLayer.EditData
             }
         }
 
+        /// <summary>
+        /// Removes the edit from the edit cache if the row is no longer dirty
+        /// </summary>
+        /// <param name="rowId">ID of the update to cleanup</param>
+        /// <param name="editCellResult">Result with row dirty flag</param>
+        private void CleanupEditIfRowClean(long rowId, EditCellResult editCellResult)
+        {
+            // If the row is still dirty, don't do anything
+            if (editCellResult.IsRowDirty)
+            {
+                return;
+            }
+
+            // Make an attempt to remove the clean row edit. If this fails, it'll be handled on commit attempt.
+            RowEditBase removedRow;
+            EditCache.TryRemove(rowId, out removedRow);
+        }
+
         #endregion
 
         /// <summary>

src/Microsoft.SqlTools.ServiceLayer/EditData/UpdateManagement/CellUpdate.cs

@@ -6,6 +6,7 @@
 using System;
 using System.Globalization;
 using System.Text.RegularExpressions;
+using Microsoft.SqlTools.ServiceLayer.EditData.Contracts;
 using Microsoft.SqlTools.ServiceLayer.QueryExecution.Contracts;
 using Microsoft.SqlTools.Utility;
 
@@ -101,6 +102,14 @@ namespace Microsoft.SqlTools.ServiceLayer.EditData.UpdateManagement
             }
         }
 
+        /// <summary>
+        /// Generates a new EditCell that represents the contents of the cell update
+        /// </summary>
+        public EditCell AsEditCell
+        {
+            get { return new EditCell(AsDbCellValue, true); }
+        }
+
         /// <summary>
         /// The column that the cell will be placed in
         /// </summary>

src/Microsoft.SqlTools.ServiceLayer/EditData/UpdateManagement/RowCreate.cs

@@ -184,14 +184,16 @@ namespace Microsoft.SqlTools.ServiceLayer.EditData.UpdateManagement
         /// </summary>
         /// <param name="columnId">The ordinal ID of the cell to reset</param>
         /// <returns>The default value for the column, or null if no default is defined</returns>
-        public override string RevertCell(int columnId)
+        public override EditRevertCellResult RevertCell(int columnId)
         {
             // Validate that the column can be reverted
             Validate.IsWithinRange(nameof(columnId), columnId, 0, newCells.Length - 1);
 
             // Remove the cell update from list of set cells
             newCells[columnId] = null;
-            return null;                // @TODO: Return default value when we have support checked in
+            return new EditRevertCellResult {IsRowDirty = true, Cell = null};
+            // @TODO: Return default value when we have support checked in
+            // @TODO: RETURN THE DEFAULT VALUE
         }
 
         /// <summary>
@@ -212,14 +214,11 @@ namespace Microsoft.SqlTools.ServiceLayer.EditData.UpdateManagement
             newCells[columnId] = update;
 
             // Put together a result of the change
-            EditUpdateCellResult eucr = new EditUpdateCellResult
+            return new EditUpdateCellResult
             {
-                HasCorrections = update.ValueAsString != newValue,
-                NewValue = update.ValueAsString != newValue ? update.ValueAsString : null,
-                IsNull = update.Value == DBNull.Value,
-                IsRevert = false            // Editing cells of new rows cannot be reverts
-            }; 
-            return eucr;
+                IsRowDirty = true,                // Row creates will always be dirty
+                Cell = update.AsEditCell
+            };
         }
 
         #endregion

src/Microsoft.SqlTools.ServiceLayer/EditData/UpdateManagement/RowDelete.cs

@@ -105,7 +105,7 @@ namespace Microsoft.SqlTools.ServiceLayer.EditData.UpdateManagement
         /// deletion.
         /// </summary>
         /// <param name="columnId">Ordinal of the column to update</param>
-        public override string RevertCell(int columnId)
+        public override EditRevertCellResult RevertCell(int columnId)
         {
             throw new InvalidOperationException(SR.EditDataDeleteSetCell);
         }

src/Microsoft.SqlTools.ServiceLayer/EditData/UpdateManagement/RowEdit.cs

@@ -109,7 +109,7 @@ namespace Microsoft.SqlTools.ServiceLayer.EditData.UpdateManagement
         /// </summary>
         /// <param name="columnId">Ordinal ID of the column to revert</param>
         /// <returns>String value of the original value of the cell</returns>
-        public abstract string RevertCell(int columnId);
+        public abstract EditRevertCellResult RevertCell(int columnId);
 
         /// <summary>
         /// Changes the value a cell in the row.

src/Microsoft.SqlTools.ServiceLayer/EditData/UpdateManagement/RowUpdate.cs

@@ -3,7 +3,6 @@
 // Licensed under the MIT license. See LICENSE file in the project root for full license information.
 //
 
-using System;
 using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.Data;
@@ -167,15 +166,21 @@ namespace Microsoft.SqlTools.ServiceLayer.EditData.UpdateManagement
         /// </summary>
         /// <param name="columnId">Ordinal of the column to revert</param>
         /// <returns>The value that was </returns>
-        public override string RevertCell(int columnId)
+        public override EditRevertCellResult RevertCell(int columnId)
         {
             Validate.IsWithinRange(nameof(columnId), columnId, 0, associatedRow.Count - 1);
 
             // Remove the cell update
+            // NOTE: This is best effort. The only way TryRemove can fail is if it is already
+            //       removed. If this happens, it is OK.
             CellUpdate cellUpdate;
             cellUpdates.TryRemove(columnId, out cellUpdate);
 
-            return associatedRow[columnId].DisplayValue;
+            return new EditRevertCellResult
+            {
+                IsRowDirty = cellUpdates.Count > 0,
+                Cell = new EditCell(associatedRow[columnId], false)
+            };
         }
 
         /// <summary>
@@ -203,10 +208,8 @@ namespace Microsoft.SqlTools.ServiceLayer.EditData.UpdateManagement
                 cellUpdates.TryRemove(columnId, out cu);
                 return new EditUpdateCellResult
                 {
-                    HasCorrections = false,
-                    NewValue = associatedRow[columnId].DisplayValue,
-                    IsRevert = true,
-                    IsNull = associatedRow[columnId].IsNull
+                    IsRowDirty = cellUpdates.Count > 0,
+                    Cell = new EditCell(associatedRow[columnId], false)
                 };
             }
 
@@ -214,10 +217,8 @@ namespace Microsoft.SqlTools.ServiceLayer.EditData.UpdateManagement
             cellUpdates.AddOrUpdate(columnId, update, (i, cu) => update);
             return new EditUpdateCellResult
             {
-                HasCorrections = update.ValueAsString != newValue,
-                NewValue = update.ValueAsString != newValue ? update.ValueAsString : null,
-                IsNull = update.Value == DBNull.Value,
-                IsRevert = false            // If we're in this branch, it is not a revert
+                IsRowDirty = true,
+                Cell = update.AsEditCell
             };
         }