Stop the timer when resetting a dynamic interval

Resetting only forgot the key, so the pending timeout still fired and
rescheduled itself: the sidebar kept reloading repos every 5 seconds
after nothing was left to replicate, and after it unmounted.

src/lib/interval.ts

@@ -20,5 +20,6 @@ export function dynamicInterval(
 }
 
 export function resetDynamicInterval(key: string) {
+  clearTimeout(dynamicIntervals.get(key));
   dynamicIntervals.delete(key);
 }

tests/unit/interval.test.ts

@@ -0,0 +1,74 @@
+import { afterEach, beforeEach, expect, test, vi } from "vitest";
+
+import { dynamicInterval, resetDynamicInterval } from "@app/lib/interval";
+
+beforeEach(() => {
+  vi.useFakeTimers();
+});
+
+afterEach(() => {
+  resetDynamicInterval("a");
+  resetDynamicInterval("b");
+  vi.useRealTimers();
+});
+
+test("runs the callback once per period", () => {
+  const callback = vi.fn();
+  dynamicInterval("a", callback, 100);
+
+  vi.advanceTimersByTime(99);
+  expect(callback).not.toHaveBeenCalled();
+  vi.advanceTimersByTime(1);
+  expect(callback).toHaveBeenCalledTimes(1);
+  vi.advanceTimersByTime(200);
+  expect(callback).toHaveBeenCalledTimes(3);
+});
+
+test("rescheduling a key replaces its callback and period", () => {
+  const first = vi.fn();
+  const second = vi.fn();
+  dynamicInterval("a", first, 100);
+  vi.advanceTimersByTime(50);
+  dynamicInterval("a", second, 300);
+
+  vi.advanceTimersByTime(299);
+  expect(first).not.toHaveBeenCalled();
+  expect(second).not.toHaveBeenCalled();
+  vi.advanceTimersByTime(1);
+  expect(second).toHaveBeenCalledTimes(1);
+});
+
+test("an async callback can reschedule its own key", async () => {
+  const callback = vi.fn(async () => {
+    await Promise.resolve();
+    dynamicInterval("a", callback, 500);
+  });
+  dynamicInterval("a", callback, 100);
+
+  await vi.advanceTimersByTimeAsync(100);
+  expect(callback).toHaveBeenCalledTimes(1);
+  await vi.advanceTimersByTimeAsync(499);
+  expect(callback).toHaveBeenCalledTimes(1);
+  await vi.advanceTimersByTimeAsync(1);
+  expect(callback).toHaveBeenCalledTimes(2);
+});
+
+test("resetting a key stops its callback", () => {
+  const callback = vi.fn();
+  dynamicInterval("a", callback, 100);
+  resetDynamicInterval("a");
+
+  vi.advanceTimersByTime(1000);
+  expect(callback).not.toHaveBeenCalled();
+});
+
+test("keys run independently", () => {
+  const a = vi.fn();
+  const b = vi.fn();
+  dynamicInterval("a", a, 100);
+  dynamicInterval("b", b, 100);
+
+  vi.advanceTimersByTime(100);
+  expect(a).toHaveBeenCalledTimes(1);
+  expect(b).toHaveBeenCalledTimes(1);
+});