diff outputs instead of replacing the whole outputs array.

src/vs/workbench/contrib/notebook/browser/viewModel/codeCellViewModel.ts

@@ -74,7 +74,9 @@ export class CodeCellViewModel extends BaseCellViewModel implements ICellViewMod
 	) {
 		super(viewType, model, UUID.generateUuid(), configurationService);
 		this._register(this.model.onDidChangeOutputs((splices) => {
-			this._outputCollection = new Array(this.model.outputs.length);
+			splices.reverse().forEach(splice => {
+				this._outputCollection.splice(splice[0], splice[1], ...splice[2].map(() => 0));
+			});
 			this._outputsTop = null;
 			this._onDidChangeOutputs.fire(splices);
 		}));

src/vs/workbench/contrib/notebook/common/model/notebookTextModel.ts

@@ -8,13 +8,15 @@ import { Emitter, Event } from 'vs/base/common/event';
 import { Disposable, dispose, IDisposable } from 'vs/base/common/lifecycle';
 import { URI } from 'vs/base/common/uri';
 import { NotebookCellTextModel } from 'vs/workbench/contrib/notebook/common/model/notebookCellTextModel';
-import { INotebookTextModel, NotebookCellOutputsSplice, NotebookDocumentMetadata, NotebookCellMetadata, ICellEditOperation, CellEditType, CellUri, notebookDocumentMetadataDefaults, diff, NotebookCellsChangeType, ICellDto2, TransientOptions, NotebookTextModelChangedEvent, NotebookRawContentEvent } from 'vs/workbench/contrib/notebook/common/notebookCommon';
+import { INotebookTextModel, NotebookCellOutputsSplice, NotebookDocumentMetadata, NotebookCellMetadata, ICellEditOperation, CellEditType, CellUri, notebookDocumentMetadataDefaults, diff, NotebookCellsChangeType, ICellDto2, TransientOptions, NotebookTextModelChangedEvent, NotebookRawContentEvent, IProcessedOutput, CellOutputKind } from 'vs/workbench/contrib/notebook/common/notebookCommon';
 import { ITextSnapshot } from 'vs/editor/common/model';
 import { IUndoRedoService, UndoRedoElementType, IUndoRedoElement, IResourceUndoRedoElement } from 'vs/platform/undoRedo/common/undoRedo';
 import { MoveCellEdit, SpliceCellsEdit, CellMetadataEdit } from 'vs/workbench/contrib/notebook/common/model/cellEdit';
 import { ITextModelService } from 'vs/editor/common/services/resolverService';
 import { IModeService } from 'vs/editor/common/services/modeService';
 import { IRange } from 'vs/editor/common/core/range';
+import { ISequence, LcsDiff } from 'vs/base/common/diff/diff';
+import { hash } from 'vs/base/common/hash';
 
 export class NotebookTextModelSnapshot implements ITextSnapshot {
 
@@ -329,8 +331,7 @@ export class NotebookTextModel extends Disposable implements INotebookTextModel
 					//TODO@joh,@rebornix no event, no undo stop (?)
 					this._assertIndex(edit.index);
 					const cell = this._cells[edit.index];
-					// TODO@rebornix, we should do diff first
-					this._spliceNotebookCellOutputs(cell.handle, [[0, cell.outputs.length, edit.outputs]], computeUndoRedo);
+					this._spliceNotebookCellOutputs2(cell.handle, edit.outputs, computeUndoRedo);
 					break;
 				case CellEditType.OutputsSplice:
 					{
@@ -645,6 +646,18 @@ export class NotebookTextModel extends Disposable implements INotebookTextModel
 		this._eventEmitter.emit({ kind: NotebookCellsChangeType.ChangeLanguage, index: this._cells.indexOf(cell), language: languageId, transient: false }, true);
 	}
 
+	private _spliceNotebookCellOutputs2(cellHandle: number, outputs: IProcessedOutput[], computeUndoRedo: boolean): void {
+		const cell = this._mapping.get(cellHandle);
+		if (!cell) {
+			return;
+		}
+
+		const diff = new LcsDiff(new OutputSequence(cell.outputs), new OutputSequence(outputs));
+		const diffResult = diff.ComputeDiff(false);
+		const splices: NotebookCellOutputsSplice[] = diffResult.changes.map(change => [change.originalStart, change.originalLength, outputs.slice(change.modifiedStart, change.modifiedStart + change.modifiedLength)]);
+		this._spliceNotebookCellOutputs(cellHandle, splices, computeUndoRedo);
+	}
+
 	private _spliceNotebookCellOutputs(cellHandle: number, splices: NotebookCellOutputsSplice[], computeUndoRedo: boolean): void {
 		const cell = this._mapping.get(cellHandle);
 		if (cell) {
@@ -695,3 +708,22 @@ export class NotebookTextModel extends Disposable implements INotebookTextModel
 		}
 	}
 }
+
+class OutputSequence implements ISequence {
+	constructor(readonly outputs: IProcessedOutput[]) {
+	}
+
+	getElements(): Int32Array | number[] | string[] {
+		return this.outputs.map(output => {
+			switch (output.outputKind) {
+				case CellOutputKind.Rich:
+					return hash([output.outputKind, output.metadata, output.data]);
+				case CellOutputKind.Error:
+					return hash([output.outputKind, output.ename, output.evalue, output.traceback]);
+				case CellOutputKind.Text:
+					return hash([output.outputKind, output.text]);
+			}
+		});
+	}
+
+}