debug: cancel hover evaluate requests when hovering off dialog

Fixes https://github.com/microsoft/vscode/issues/91457

src/vs/workbench/contrib/debug/browser/debugEditorContribution.ts

@@ -355,7 +355,7 @@ export class DebugEditorContribution implements IDebugEditorContribution {
 	}
 
 	private hideHoverWidget(): void {
-		if (!this.hideHoverScheduler.isScheduled() && this.hoverWidget.isVisible()) {
+		if (!this.hideHoverScheduler.isScheduled() && this.hoverWidget.willBeVisible()) {
 			this.hideHoverScheduler.schedule();
 		}
 		this.showHoverScheduler.cancel();

src/vs/workbench/contrib/debug/browser/debugHover.ts

@@ -31,7 +31,7 @@ import { coalesce } from 'vs/base/common/arrays';
 import { IAsyncDataSource } from 'vs/base/browser/ui/tree/tree';
 import { VariablesRenderer } from 'vs/workbench/contrib/debug/browser/variablesView';
 import { EvaluatableExpressionProviderRegistry } from 'vs/editor/common/modes';
-import { CancellationToken } from 'vs/base/common/cancellation';
+import { CancellationTokenSource } from 'vs/base/common/cancellation';
 
 const $ = dom.$;
 
@@ -70,6 +70,7 @@ export class DebugHoverWidget implements IContentWidget {
 	allowEditorOverflow = true;
 
 	private _isVisible: boolean;
+	private showCancellationSource?: CancellationTokenSource;
 	private domNode!: HTMLElement;
 	private tree!: AsyncDataTree<IExpression, IExpression, any>;
 	private showAtPosition: Position | null;
@@ -161,13 +162,17 @@ export class DebugHoverWidget implements IContentWidget {
 	}
 
 	isHovered(): boolean {
-		return this.domNode.matches(':hover');
+		return !!this.domNode?.matches(':hover');
 	}
 
 	isVisible(): boolean {
 		return this._isVisible;
 	}
 
+	willBeVisible(): boolean {
+		return !!this.showCancellationSource;
+	}
+
 	getId(): string {
 		return DebugHoverWidget.ID;
 	}
@@ -177,6 +182,8 @@ export class DebugHoverWidget implements IContentWidget {
 	}
 
 	async showAt(range: Range, focus: boolean): Promise<void> {
+		this.showCancellationSource?.cancel();
+		const cancellationSource = this.showCancellationSource = new CancellationTokenSource();
 		const session = this.debugService.getViewModel().focusedSession;
 
 		if (!session || !this.editor.hasModel()) {
@@ -193,7 +200,7 @@ export class DebugHoverWidget implements IContentWidget {
 			const supports = EvaluatableExpressionProviderRegistry.ordered(model);
 
 			const promises = supports.map(support => {
-				return Promise.resolve(support.provideEvaluatableExpression(model, pos, CancellationToken.None)).then(expression => {
+				return Promise.resolve(support.provideEvaluatableExpression(model, pos, cancellationSource.token)).then(expression => {
 					return expression;
 				}, err => {
 					//onUnexpectedExternalError(err);
@@ -236,7 +243,7 @@ export class DebugHoverWidget implements IContentWidget {
 			}
 		}
 
-		if (!expression || (expression instanceof Expression && !expression.available)) {
+		if (cancellationSource.token.isCancellationRequested || !expression || (expression instanceof Expression && !expression.available)) {
 			this.hide();
 			return;
 		}
@@ -315,6 +322,11 @@ export class DebugHoverWidget implements IContentWidget {
 
 
 	hide(): void {
+		if (this.showCancellationSource) {
+			this.showCancellationSource.cancel();
+			this.showCancellationSource = undefined;
+		}
+
 		if (!this._isVisible) {
 			return;
 		}