fix #64999

src/vs/base/common/labels.ts

@@ -366,7 +366,7 @@ export function mnemonicMenuLabel(label: string, forceDisableMnemonics?: boolean
 
 /**
  * Handles mnemonics for buttons. Depending on OS:
- * - Windows: Supported via & character (replace && with &)
+ * - Windows: Supported via & character (replace && with & and & with && for escaping)
  * -   Linux: Supported via _ character (replace && with _)
  * -   macOS: Unsupported (replace && with empty string)
  */
@@ -375,7 +375,11 @@ export function mnemonicButtonLabel(label: string): string {
 		return label.replace(/\(&&\w\)|&&/g, '');
 	}
 
-	return label.replace(/&&/g, isWindows ? '&' : '_');
+	if (isWindows) {
+		return label.replace(/&&|&/g, m => m === '&' ? '&&' : '&');
+	}
+
+	return label.replace(/&&/g, '_');
 }
 
 export function unmnemonicLabel(label: string): string {

src/vs/base/test/common/labels.test.ts

@@ -164,4 +164,19 @@ suite('Labels', () => {
 		assert.equal(labels.getBaseLabel('c:\\some\\folder\\file.txt'), 'file.txt');
 		assert.equal(labels.getBaseLabel('c:\\some\\folder'), 'folder');
 	});
+
+	test('mnemonicButtonLabel', () => {
+		assert.equal(labels.mnemonicButtonLabel('Hello World'), 'Hello World');
+		assert.equal(labels.mnemonicButtonLabel(''), '');
+		if (platform.isWindows) {
+			assert.equal(labels.mnemonicButtonLabel('Hello & World'), 'Hello && World');
+			assert.equal(labels.mnemonicButtonLabel('Do &&not Save & Continue'), 'Do &not Save && Continue');
+		} else if (platform.isMacintosh) {
+			assert.equal(labels.mnemonicButtonLabel('Hello & World'), 'Hello & World');
+			assert.equal(labels.mnemonicButtonLabel('Do &&not Save & Continue'), 'Do not Save & Continue');
+		} else {
+			assert.equal(labels.mnemonicButtonLabel('Hello & World'), 'Hello & World');
+			assert.equal(labels.mnemonicButtonLabel('Do &&not Save & Continue'), 'Do _not Save & Continue');
+		}
+	});
 });
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