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/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
             };
         }