Settings editor - autofix missing commas in settings file.

Fixes #42232

extensions/configuration-editing/src/extension.ts

@@ -7,7 +7,7 @@
 import * as nls from 'vscode-nls';
 const localize = nls.loadMessageBundle();
 import * as vscode from 'vscode';
-import { getLocation, visit, parse } from 'jsonc-parser';
+import { getLocation, visit, parse, ParseError, ParseErrorCode } from 'jsonc-parser';
 import * as path from 'path';
 import { SettingsDocument } from './settingsDocumentHelper';
 
@@ -42,6 +42,47 @@ export function activate(context: vscode.ExtensionContext): void {
 		}
 	}, null, context.subscriptions));
 	updateLaunchJsonDecorations(vscode.window.activeTextEditor);
+
+	context.subscriptions.push(vscode.workspace.onWillSaveTextDocument(e => {
+		if (!e.document.fileName.endsWith('/settings.json')) {
+			return;
+		}
+
+		autoFixSettingsJSON(e);
+	}));
+}
+
+function autoFixSettingsJSON(willSaveEvent: vscode.TextDocumentWillSaveEvent): void {
+	const document = willSaveEvent.document;
+	const text = document.getText();
+	const edit = new vscode.WorkspaceEdit();
+
+	let lastEndOfSomething = -1;
+	visit(text, {
+		onArrayEnd(offset: number, length: number): void {
+			lastEndOfSomething = offset + length;
+		},
+
+		onLiteralValue(value: any, offset: number, length: number): void {
+			lastEndOfSomething = offset + length;
+		},
+
+		onObjectEnd(offset: number, length: number): void {
+			lastEndOfSomething = offset + length;
+		},
+
+		onError(error: ParseErrorCode, offset: number, length: number): void {
+			if (error === ParseErrorCode.CommaExpected && lastEndOfSomething > -1) {
+				const errorPosition = document.positionAt(offset);
+
+				const fixPosition = document.positionAt(lastEndOfSomething);
+				edit.insert(document.uri, fixPosition, ',');
+			}
+		}
+	});
+
+	willSaveEvent.waitUntil(
+		vscode.workspace.applyEdit(edit));
 }
 
 function registerKeybindingsCompletions(): vscode.Disposable {