strict null checks

#60565

src/tsconfig.strictNullChecks.json

@@ -145,6 +145,7 @@
 		"./vs/editor/common/services/modeService.ts",
 		"./vs/editor/common/services/modelService.ts",
 		"./vs/editor/common/services/resolverService.ts",
+		"./vs/editor/common/standalone/standaloneBase.ts",
 		"./vs/editor/common/view/overviewZoneManager.ts",
 		"./vs/editor/common/viewLayout/whitespaceComputer.ts",
 		"./vs/editor/common/viewModel/prefixSumComputer.ts",
@@ -166,6 +167,7 @@
 		"./vs/editor/test/common/model/benchmark/benchmarkUtils.ts",
 		"./vs/editor/test/common/modes/supports/javascriptOnEnterRules.ts",
 		"./vs/editor/test/common/modesTestUtils.ts",
+		"./vs/monaco.d.ts",
 		"./vs/nls.mock.ts",
 		"./vs/platform/broadcast/electron-browser/broadcastService.ts",
 		"./vs/platform/clipboard/common/clipboardService.ts",
@@ -233,6 +235,7 @@
 		"./vs/workbench/parts/search/common/constants.ts",
 		"./vs/workbench/parts/terminal/browser/terminalWidgetManager.ts",
 		"./vs/workbench/parts/terminal/common/terminal.ts",
+		"./vs/workbench/parts/terminal/node/windowsShellHelper.ts",
 		"./vs/workbench/parts/welcome/page/electron-browser/vs_code_welcome_page.ts",
 		"./vs/workbench/services/activity/common/activity.ts",
 		"./vs/workbench/services/backup/common/backup.ts",

src/vs/editor/common/standalone/standaloneBase.ts

@@ -231,8 +231,8 @@ export enum KeyCode {
 
 export function createMonacoBaseAPI(): typeof monaco {
 	return {
-		editor: undefined,
-		languages: undefined,
+		editor: undefined!, // undefined override expected here
+		languages: undefined!, // undefined override expected here
 		CancellationTokenSource: CancellationTokenSource,
 		Emitter: Emitter,
 		KeyCode: KeyCode,

src/vs/platform/commands/common/commands.ts

@@ -124,7 +124,7 @@ export const CommandsRegistry: ICommandRegistry = new class implements ICommandR
 export const NullCommandService: ICommandService = {
 	_serviceBrand: undefined,
 	onWillExecuteCommand: () => ({ dispose: () => { } }),
-	executeCommand() {
-		return Promise.resolve(undefined);
+	executeCommand<T = any>() {
+		return Promise.resolve<T>(undefined);
 	}
 };

src/vs/workbench/parts/terminal/node/windowsShellHelper.ts

@@ -27,7 +27,7 @@ let windowsProcessTree: typeof WindowsProcessTreeType;
 export class WindowsShellHelper {
 	private _onCheckShell: Emitter<Promise<string>>;
 	private _isDisposed: boolean;
-	private _currentRequest: Promise<string>;
+	private _currentRequest: Promise<string> | null;
 	private _newLineFeed: boolean;
 
 	public constructor(