cache-manager: wrap() method - support refreshThreshold argument as number or Function - (value:T) => number. similar to how ttl is supported

Author: yaronyam

packages/cache-manager/src/index.ts

@@ -41,7 +41,7 @@ export type Cache = {
 		key: string,
 		fnc: () => T | Promise<T>,
 		ttl?: number | ((value: T) => number),
-		refreshThreshold?: number
+		refreshThreshold?: number | ((value: T) => number)
 	) => Promise<T>;
 	on: <E extends keyof Events>(
 		event: E,
@@ -252,7 +252,7 @@ export const createCache = (options?: CreateCacheOptions): Cache => {
 		key: string,
 		fnc: () => T | Promise<T>,
 		ttl?: number | ((value: T) => number),
-		refreshThreshold?: number,
+		refreshThreshold?: number | ((value: T) => number),
 	): Promise<T> => coalesceAsync(`${_cacheId}::${key}`, async () => {
 		let value: T | undefined;
 		let i = 0;
@@ -281,7 +281,7 @@ export const createCache = (options?: CreateCacheOptions): Cache => {
 			return result;
 		}
 
-		const shouldRefresh = lt(remainingTtl, refreshThreshold ?? options?.refreshThreshold);
+		const shouldRefresh = lt(remainingTtl, runIfFn(refreshThreshold, value)  ?? options?.refreshThreshold);
 
 		if (shouldRefresh) {
 			coalesceAsync(`+++${_cacheId}__${key}`, fnc)

packages/cache-manager/test/wrap.test.ts

@@ -85,6 +85,25 @@ describe('wrap', () => {
 		expect(await cache.wrap(data.key, async () => 5, undefined, 500)).toEqual(4);
 	});
 
+	it('should allow refreshThreshold function on wrap function', async () => {
+		const config = {ttl: (v:number) => v * 1000, refreshThreshold: (v:number) => v * 500 };
+
+		// 1st call should be cached
+		expect(await cache.wrap(data.key, async () => 1, config.ttl, config.refreshThreshold)).toEqual(1);
+		await sleep(501);
+		// Background refresh, but stale value returned
+		expect(await cache.wrap(data.key, async () => 2, config.ttl, config.refreshThreshold)).toEqual(1);
+		// New value in cache
+		expect(await cache.wrap(data.key, async () => 2, config.ttl, config.refreshThreshold)).toEqual(2);
+		await sleep(1001);
+		// No background refresh with the new override params
+		expect(await cache.wrap(data.key, async () => 3, undefined, 500)).toEqual(2);
+		await sleep(500);
+		// Background refresh, but stale value returned
+		expect(await cache.wrap(data.key, async () => 4, undefined, 500)).toEqual(2);
+		expect(await cache.wrap(data.key, async () => 5, undefined, 500)).toEqual(4);
+	});
+
 	it('should support nested calls of other caches - no mutual state', async () => {
 		const getValueA = vi.fn(() => 'A');
 		const getValueB = vi.fn(() => 'B');