* Implements languageId support

* Implements typing of helper functions
* Shift+F1 opens a new debug visualizer window if none is opened yet

extension/src/EvaluationWatchService/EvaluationEngine/EvaluationEngine.ts

@@ -16,6 +16,11 @@ export interface Evaluator {
 		| { kind: "data"; result: DataExtractionResult }
 		| { kind: "error"; message: FormattedMessage }
 	>;
+
+	/**
+	 * The language that expressions must be written in.
+	 */
+	readonly languageId: string | undefined;
 }
 
 export interface EvaluationArgs {

extension/src/EvaluationWatchService/EvaluationEngine/GenericEvaluationEngine.ts

@@ -22,6 +22,8 @@ export class GenericEvaluationEngine implements EvaluationEngine {
 }
 
 export class GenericEvaluator implements Evaluator {
+	public readonly languageId = "text";
+
 	constructor(private readonly session: VsCodeDebugSession) {}
 
 	public async evaluate({

extension/src/EvaluationWatchService/EvaluationEngine/JsEvaluationEngine.ts

@@ -33,6 +33,8 @@ export class JsEvaluationEngine implements EvaluationEngine {
 }
 
 class JsEvaluator implements Evaluator {
+	public readonly languageId = "javascript";
+
 	constructor(private readonly session: VsCodeDebugSession) {}
 
 	public async evaluate({

extension/src/EvaluationWatchService/EvaluationWatchService.ts

@@ -8,6 +8,13 @@ export interface EvaluationWatchService {
 	): EvaluationWatcher;
 
 	getCompletions(text: string, column: number): Promise<CompletionItem[]>;
+
+	/**
+	 * The language the expressions must be written in.
+	 * `undefined`, if unknown.
+	 * This field is observable.
+	 */
+	readonly languageId: string | undefined;
 }
 
 export interface EvaluationWatcherOptions {

extension/src/EvaluationWatchService/EvaluationWatchServiceImpl.ts

@@ -18,7 +18,7 @@ export class EvaluationWatchServiceImpl implements EvaluationWatchService {
 
 	constructor(
 		private readonly vsCodeDebuggerView: VsCodeDebuggerView,
-		private readonly dataExtractionProviderFactory: EvaluationEngine
+		private readonly evaluationEngine: EvaluationEngine
 	) {
 		this.dispose.track({
 			dispose: autorun(() => {
@@ -48,6 +48,21 @@ export class EvaluationWatchServiceImpl implements EvaluationWatchService {
 		this.watchers.delete(w);
 	}
 
+	private lastLanguageId: string | undefined = undefined;
+
+	get languageId(): string | undefined {
+		const session = this.vsCodeDebuggerView.activeDebugSession;
+		if (!session) {
+			return this.lastLanguageId;
+		}
+		const evaluator = this.evaluationEngine.createEvaluator(session);
+		if (!evaluator) {
+			return this.lastLanguageId;
+		}
+		this.lastLanguageId = evaluator.languageId;
+		return evaluator.languageId;
+	}
+
 	public async refresh(w: ObservableEvaluationWatcher): Promise<void> {
 		const session = this.vsCodeDebuggerView.activeDebugSession;
 		if (!session) {
@@ -59,10 +74,8 @@ export class EvaluationWatchServiceImpl implements EvaluationWatchService {
 
 		w._state = { kind: "loading" };
 
-		const extractionProvider = this.dataExtractionProviderFactory.createEvaluator(
-			session
-		);
-		if (!extractionProvider) {
+		const evaluator = this.evaluationEngine.createEvaluator(session);
+		if (!evaluator) {
 			w._state = {
 				kind: "error",
 				message: `The debug adapter "${session.session.type}" is not supported.`,
@@ -70,7 +83,7 @@ export class EvaluationWatchServiceImpl implements EvaluationWatchService {
 			return;
 		}
 
-		const result = await extractionProvider.evaluate({
+		const result = await evaluator.evaluate({
 			expression: w.expression,
 			frameId,
 			preferredExtractorId: w.preferredDataExtractor,