Support waiting for promise in Collector.wait

README.md

@@ -31,7 +31,7 @@ Async collection is an utility to collect needed keys and signalize on done.
   - `options.exact?: boolean`
   - `options.timeout?: number`
 - `set(key: string, value: unknown)`
-- `wait(key: string, fn: AsyncFunction, ...args?: Array<unknown>)`
+- `wait(key: string, fn: AsyncFunction | Promise<unknown>, ...args?: Array<unknown>)`
 - `take(key: string, fn: Function, ...args?: Array<unknown>)`
 - `collect(sources: Record<string, Collector>)`
 - `fail(error: Error)`
@@ -92,6 +92,62 @@ dc.collect({ key1, key3 });
 const result = await ac;
 ```
 
+Complex example: compare `Promise.all` and `Collector` in next two examples:
+
+```js
+// Collect 4 keys from different contracts with Promise.all
+
+const promise1 = new Promise((resolve, reject) => {
+  fs.readFile('README.md', (err, data) => {
+    if (err) return void reject(err);
+    resolve(data);
+  });
+});
+
+const promise2 = fs.promises.readFile('README.md');
+const url = 'http://worldtimeapi.org/api/timezone/Europe';
+
+const promise3 = fetch(url).then((data) => data.json());
+
+const promise4 = new Promise((resolve) => {
+  setTimeout(() => {
+    resolve('value4');
+  }, 50);
+});
+
+const [key1, key2, key3, key4] = await Promise.all([
+  promise1,
+  promise2,
+  promise3,
+  promise4,
+]);
+const result = { key1, key2, key3, key4 };
+console.log(result);
+```
+
+Compare with:
+
+```js
+// Collect 4 keys from different contracts with Collector
+
+const dc = collect(['key1', 'key2', 'key3', 'key4']);
+
+dc.take('key1', fs.readFile, 'README.md');
+
+dc.wait('key2', fs.promises.readFile, 'README.md');
+
+const url = 'http://worldtimeapi.org/api/timezone/Europe';
+dc.wait(
+  'key3',
+  fetch(url).then((data) => data.json()),
+);
+
+setTimeout(() => dc.set('key4', 'value4'), 50);
+
+const result = await dc;
+console.log(result);
+```
+
 ## Crypto utilities
 
 - `cryptoRandom(min?: number, max?: number): number`

lib/collector.js

@@ -54,7 +54,8 @@ class Collector {
   }
 
   wait(key, fn, ...args) {
-    fn(...args).then(
+    const promise = fn instanceof Promise ? fn : fn(...args);
+    promise.then(
       (data) => this.set(key, data),
       (err) => this.fail(err),
     );

metautil.d.ts

@@ -248,7 +248,11 @@ export class Collector {
   timeout: number;
   constructor(keys: Array<string>, options?: CollectorOptions);
   set(key: string, value: unknown): void;
-  wait(key: string, fn: AsyncFunction, ...args: Array<unknown>): void;
+  wait(
+    key: string,
+    fn: AsyncFunction | Promise<unknown>,
+    ...args: Array<unknown>
+  ): void;
   take(key: string, fn: Function, ...args: Array<unknown>): void;
   collect(sources: Record<string, Collector>): void;
   fail(error: Error): void;

test/collector.js

@@ -143,6 +143,20 @@ metatests.test('Collector: wait', async (test) => {
   test.end();
 });
 
+metatests.test('Collector: wait for promise', async (test) => {
+  const expectedResult = { key1: 'User: Marcus' };
+  const dc = collect(['key1']);
+
+  const promise = new Promise((resolve) => {
+    setTimeout(() => resolve('User: Marcus'), 100);
+  });
+  dc.wait('key1', promise);
+
+  const result = await dc;
+  test.strictSame(result, expectedResult);
+  test.end();
+});
+
 metatests.test('Collector: compose collect', async (test) => {
   const expectedResult = { key1: { sub1: 11 }, key2: 2, key3: { sub3: 31 } };
   const dc = collect(['key1', 'key2', 'key3']);