Seed shuffle of recommended extensions per session

src/vs/base/common/arrays.ts

@@ -470,14 +470,19 @@ export function arrayInsert<T>(target: T[], insertIndex: number, insertArr: T[])
  * Uses Fisher-Yates shuffle to shuffle the given array
  * @param array
  */
-export function shuffle<T>(array: T[]): void {
-	var i = 0
-		, j = 0
-		, temp = null;
-
-	for (i = array.length - 1; i > 0; i -= 1) {
-		j = Math.floor(Math.random() * (i + 1));
-		temp = array[i];
+export function shuffle<T>(array: T[], seed?: number): void {
+	// Seeded random number generator in JS. Modified from:
+	// https://stackoverflow.com/questions/521295/seeding-the-random-number-generator-in-javascript
+	const random = () => {
+		var x = Math.sin(seed++) * 179426549; // throw away most significant digits and reduce any potential bias
+		return x - Math.floor(x);
+	};
+
+	const rand = typeof seed === 'number' ? random : Math.random;
+
+	for (let i = array.length - 1; i > 0; i -= 1) {
+		let j = Math.floor(rand() * (i + 1));
+		let temp = array[i];
 		array[i] = array[j];
 		array[j] = temp;
 	}

src/vs/workbench/parts/extensions/electron-browser/extensionTipsService.ts

@@ -86,6 +86,7 @@ export class ExtensionTipsService extends Disposable implements IExtensionTipsSe
 
 	private readonly _onRecommendationChange: Emitter<RecommendationChangeNotification> = new Emitter<RecommendationChangeNotification>();
 	onRecommendationChange: Event<RecommendationChangeNotification> = this._onRecommendationChange.event;
+	private sessionSeed: number;
 
 	constructor(
 		@IExtensionGalleryService private readonly _galleryService: IExtensionGalleryService,
@@ -108,7 +109,6 @@ export class ExtensionTipsService extends Disposable implements IExtensionTipsSe
 	) {
 		super();
 
-
 		if (!this.isEnabled()) {
 			return;
 		}
@@ -117,6 +117,8 @@ export class ExtensionTipsService extends Disposable implements IExtensionTipsSe
 			this._extensionsRecommendationsUrl = product.extensionsGallery.recommendationsUrl;
 		}
 
+		this.sessionSeed = +new Date();
+
 		let globallyIgnored = <string[]>JSON.parse(this.storageService.get('extensionsAssistant/ignored_recommendations', StorageScope.GLOBAL, '[]'));
 		this._globallyIgnoredRecommendations = globallyIgnored.map(id => id.toLowerCase());
 
@@ -405,7 +407,7 @@ export class ExtensionTipsService extends Disposable implements IExtensionTipsSe
 				...this._dynamicWorkspaceRecommendations,
 				...Object.keys(this._experimentalRecommendations),
 			]).filter(extensionId => this.isExtensionAllowedToBeRecommended(extensionId));
-			shuffle(others);
+			shuffle(others, this.sessionSeed);
 			return others.map(extensionId => {
 				const sources: ExtensionRecommendationSource[] = [];
 				if (this._exeBasedRecommendations[extensionId]) {