Support reverting cell metadata & cell language in notebook diff view (microsoft#226747)

Author: DonJayamanne

src/vs/workbench/contrib/notebook/browser/diff/diffElementViewModel.ts

@@ -824,7 +824,12 @@ export function getFormattedMetadataJSON(documentTextModel: INotebookTextModel,
 		language,
 		...filteredMetadata
 	};
-
+	// Give preference to the language we have been given.
+	// Metadata can contain `language` due to round-tripping of cell metadata.
+	// I.e. we add it here, and then from SCM when we revert the cell, we get this same metadata back with the `language` property.
+	if (language) {
+		obj.language = language;
+	}
 	const metadataSource = toFormattedString(obj, {});
 
 	return metadataSource;

src/vs/workbench/contrib/notebook/browser/diff/notebookDiffActions.ts

@@ -22,7 +22,7 @@ import { ICommandActionTitle } from 'vs/platform/action/common/action';
 import { DEFAULT_EDITOR_ASSOCIATION } from 'vs/workbench/common/editor';
 import { KeybindingWeight } from 'vs/platform/keybinding/common/keybindingsRegistry';
 import { KeyCode, KeyMod } from 'vs/base/common/keyCodes';
-import { CellEditType, NOTEBOOK_DIFF_EDITOR_ID } from 'vs/workbench/contrib/notebook/common/notebookCommon';
+import { CellEditType, ICellEditOperation, NOTEBOOK_DIFF_EDITOR_ID } from 'vs/workbench/contrib/notebook/common/notebookCommon';
 import { ITextResourceConfigurationService } from 'vs/editor/common/services/textResourceConfiguration';
 import { NotebookMultiTextDiffEditor } from 'vs/workbench/contrib/notebook/browser/diff/notebookMultiDiffEditor';
 import { Codicon } from 'vs/base/common/codicons';
@@ -307,14 +307,24 @@ registerAction2(class extends Action2 {
 			return;
 		}
 
+		if (!(context.cell instanceof SideBySideDiffElementViewModel)) {
+			return;
+		}
+
 		const original = context.cell.original;
 		const modified = context.cell.modified;
 
-		if (!original || !modified) {
+		const modifiedCellIndex = context.cell.mainDocumentTextModel.cells.indexOf(modified.textModel);
+		if (modifiedCellIndex === -1) {
 			return;
 		}
 
-		modified.textModel.metadata = original.metadata;
+		const rawEdits: ICellEditOperation[] = [{ editType: CellEditType.Metadata, index: modifiedCellIndex, metadata: original.metadata }];
+		if (context.cell.original.language && context.cell.modified.language !== context.cell.original.language) {
+			rawEdits.push({ editType: CellEditType.CellLanguage, index: modifiedCellIndex, language: context.cell.original.language });
+		}
+
+		context.cell.modifiedDocument.applyEdits(rawEdits, true, undefined, () => undefined, undefined, true);
 	}
 });
 

src/vs/workbench/contrib/notebook/browser/notebook.contribution.ts

@@ -449,7 +449,7 @@ class CellInfoContentProvider {
 					resource
 				);
 				this._disposables.push(disposables.add(ref.object.notebook.onDidChangeContent(e => {
-					if (result && e.rawEvents.some(event => event.kind === NotebookCellsChangeType.ChangeCellMetadata && event.index === cellIndex)) {
+					if (result && e.rawEvents.some(event => (event.kind === NotebookCellsChangeType.ChangeCellMetadata || event.kind === NotebookCellsChangeType.ChangeCellLanguage) && event.index === cellIndex)) {
 						const value = getFormattedMetadataJSON(ref.object.notebook, cell.metadata, cell.language);
 						if (result.getValue() !== value) {
 							result.setValue(getFormattedMetadataJSON(ref.object.notebook, cell.metadata, cell.language));