fix(app): keep quick switcher focus when results are recomputed (#1746)

fluxer_app/src/features/search/state/QuickSwitcher.tsx

@@ -19,6 +19,7 @@ import {
 	generateQueryModeResults,
 	resolveTransformedMember,
 } from '@app/features/search/state/QuickSwitcherResultGenerators';
+import {resolveRecomputedSelectedIndex} from '@app/features/search/state/QuickSwitcherSelection';
 import type {
 	CandidateSets,
 	ComputeResultsForQueryResult,
@@ -404,10 +405,11 @@ class QuickSwitcher {
 		if (options.invalidateCandidates ?? true) {
 			this.invalidateCandidateSets();
 		}
+		const previous = this.results[this.selectedIndex];
 		const {queryMode, results, selectedIndex} = this.computeResultsForQuery(this.query);
 		this.queryMode = queryMode;
 		this.results = results;
-		this.selectedIndex = selectedIndex;
+		this.selectedIndex = resolveRecomputedSelectedIndex(previous, results, selectedIndex);
 	}
 
 	private computeResultsForQuery(query: string): ComputeResultsForQueryResult {

fluxer_app/src/features/search/state/QuickSwitcherSelection.test.ts

@@ -0,0 +1,46 @@
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+import {resolveRecomputedSelectedIndex} from '@app/features/search/state/QuickSwitcherSelection';
+import type {QuickSwitcherResult} from '@app/features/search/state/QuickSwitcherTypes';
+import {QuickSwitcherResultTypes} from '@fluxer/constants/src/QuickSwitcherConstants';
+import {describe, expect, it} from 'vitest';
+
+const result = (type: QuickSwitcherResult['type'], id: string) => ({type, id}) as QuickSwitcherResult;
+
+describe('resolveRecomputedSelectedIndex', () => {
+	it('follows the focused result when the list is reordered', () => {
+		const previous = result(QuickSwitcherResultTypes.TEXT_CHANNEL, 'c3');
+		const results = [
+			result(QuickSwitcherResultTypes.TEXT_CHANNEL, 'c3'),
+			result(QuickSwitcherResultTypes.TEXT_CHANNEL, 'c1'),
+			result(QuickSwitcherResultTypes.TEXT_CHANNEL, 'c2'),
+		];
+		expect(resolveRecomputedSelectedIndex(previous, results, 0)).toBe(0);
+	});
+
+	it('keeps the focused result when entries are inserted above it', () => {
+		const previous = result(QuickSwitcherResultTypes.TEXT_CHANNEL, 'c2');
+		const results = [
+			result(QuickSwitcherResultTypes.HEADER, 'h1'),
+			result(QuickSwitcherResultTypes.TEXT_CHANNEL, 'c9'),
+			result(QuickSwitcherResultTypes.TEXT_CHANNEL, 'c2'),
+		];
+		expect(resolveRecomputedSelectedIndex(previous, results, 1)).toBe(2);
+	});
+
+	it('falls back when the focused result disappears', () => {
+		const previous = result(QuickSwitcherResultTypes.TEXT_CHANNEL, 'gone');
+		const results = [result(QuickSwitcherResultTypes.TEXT_CHANNEL, 'c1')];
+		expect(resolveRecomputedSelectedIndex(previous, results, 0)).toBe(0);
+	});
+
+	it('does not confuse ids that repeat across result types', () => {
+		const previous = result(QuickSwitcherResultTypes.GUILD, '42');
+		const results = [result(QuickSwitcherResultTypes.TEXT_CHANNEL, '42'), result(QuickSwitcherResultTypes.GUILD, '42')];
+		expect(resolveRecomputedSelectedIndex(previous, results, 0)).toBe(1);
+	});
+
+	it('uses the fallback when nothing was focused', () => {
+		expect(resolveRecomputedSelectedIndex(undefined, [result(QuickSwitcherResultTypes.GUILD, 'g')], 0)).toBe(0);
+	});
+});

fluxer_app/src/features/search/state/QuickSwitcherSelection.ts

@@ -0,0 +1,15 @@
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+import type {QuickSwitcherResult} from '@app/features/search/state/QuickSwitcherTypes';
+
+export function resolveRecomputedSelectedIndex(
+	previous: QuickSwitcherResult | undefined,
+	results: ReadonlyArray<QuickSwitcherResult>,
+	fallbackIndex: number,
+): number {
+	if (!previous) {
+		return fallbackIndex;
+	}
+	const restored = results.findIndex((result) => result.type === previous.type && result.id === previous.id);
+	return restored >= 0 ? restored : fallbackIndex;
+}