Add test for last edit mode (#18734)

* add test for persisting last edit mode

* remove empty line

* address comments

* update comment

src/sql/workbench/contrib/notebook/test/electron-browser/cell.test.ts

@@ -1358,4 +1358,64 @@ suite('Cell Model', function (): void {
 		assert(editMode);
 		assert.strictEqual(editMode, CellEditModes.WYSIWYG, 'Default edit mode should be WYSIWYG.');
 	});
+
+	test('cell should have lastEditMode set to whatever the user edited out of last', async function () {
+		let notebookModel = new NotebookModelStub({
+			name: '',
+			version: '',
+			mimetype: ''
+		});
+		let contents: nb.ICellContents = {
+			cell_type: CellTypes.Markdown,
+			source: '',
+			metadata: {}
+		};
+		let cellModel = factory.createCell(contents, { notebook: notebookModel, isTrusted: false });
+
+		// Non-Editing Preview mode -> showPreview should be true and showMarkdown should be false.
+		assert(cellModel.showPreview, 'showPreview should default to true when not in editMode');
+		assert(!cellModel.showMarkdown, 'showMarkdown should be false when not in editMode');
+
+		let getCurrentCellEditModePromise = () => {
+			return new Promise((resolve, reject) => {
+				cellModel.onCurrentEditModeChanged(cellEditMode => {
+					resolve(cellEditMode);
+				});
+			});
+		};
+
+		let cellModePromise = getCurrentCellEditModePromise();
+		// Initially mode is defaulted be WYSIWYG -> showPreview is true and showMarkdown is false
+		assert.strictEqual(cellModel.currentMode, CellEditModes.WYSIWYG, 'Current mode should be WYSIWYG when not in edit mode');
+		assert.strictEqual(cellModel.isEditMode, false, 'cell should not default to edit mode');
+
+		cellModel.isEditMode = true;
+		let lastEditMode = await cellModePromise;
+		assert.strictEqual(lastEditMode, CellEditModes.WYSIWYG, 'Default edit mode should be WYSIWYG');
+		// update mode to SPLITVIEW -> showMarkdown and showPreview both are true
+		cellModePromise = getCurrentCellEditModePromise();
+		cellModel.showMarkdown = true;
+		lastEditMode = await cellModePromise;
+		assert.strictEqual(lastEditMode, CellEditModes.SPLIT, 'LastEditMode should be set to split view');
+
+		// come out of edit mode and enter edit mode again to check edit mode.
+		cellModel.isEditMode = false;
+		assert.strictEqual(cellModel.currentMode, CellEditModes.WYSIWYG, 'Should default to WYSIWYG when not editing');
+		cellModel.isEditMode = true;
+		assert.strictEqual(cellModel.currentMode, CellEditModes.SPLIT, 'Should persist lastEditMode and be in Split View');
+
+		// update mode to markdown mode only -> showPreview is false and showMarkdown is true
+		cellModePromise = getCurrentCellEditModePromise();
+		cellModel.showPreview = false;
+		lastEditMode = await cellModePromise;
+		assert.strictEqual(lastEditMode, CellEditModes.MARKDOWN, 'LastEditMode should be set to markdown');
+
+		// come out of edit mode and enter edit mode again to check edit mode.
+		cellModel.isEditMode = false;
+		assert.strictEqual(cellModel.currentMode, CellEditModes.WYSIWYG, 'Should default to WYSIWYG when not editing');
+		cellModel.isEditMode = true;
+		assert.strictEqual(cellModel.currentMode, CellEditModes.MARKDOWN, 'Should persist lastEditMode and be in markdown only');
+
+	});
+
 });

src/sql/workbench/services/notebook/browser/models/cell.ts

@@ -241,6 +241,11 @@ export class CellModel extends Disposable implements ICellModel {
 			const newEditMode = this._lastEditMode ?? this._defaultTextEditMode;
 			this.showPreview = newEditMode !== TextCellEditModes.Markdown;
 			this.showMarkdown = newEditMode !== TextCellEditModes.RichText;
+		} else {
+			// when not in edit mode, default the values since they are only valid when editing.
+			// And to return the correct currentMode value.
+			this._showMarkdown = false;
+			this._showPreview = true;
 		}
 		this._onCellModeChanged.fire(this._isEditMode);
 		// Note: this does not require a notebook update as it does not change overall state