deno.land / x / mongoose@6.7.5 / test / docs / promises.test.js
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const assert = require('assert');const mongoose = require('../../');const start = require('../common');
describe('promises docs', function () { let Band; let db;
before(function (done) { db = mongoose.createConnection(start.uri);
Band = db.model('band-promises', {name: String, members: [String]});
done(); });
beforeEach(function (done) { Band.deleteMany({}, done); });
after(async function () { mongoose.Promise = global.Promise;
await db.close(); });
/** * Mongoose async operations, like `.save()` and queries, return thenables. * This means that you can do things like `MyModel.findOne({}).then()` and * `await MyModel.findOne({}).exec()` if you're using * [async/await](http://thecodebarbarian.com/80-20-guide-to-async-await-in-node.js.html). * * You can find the return type of specific operations [in the api docs](https://mongoosejs.com/docs/api.html) * You can also read more about [promises in Mongoose](https://masteringjs.io/tutorials/mongoose/promise). */ it('Built-in Promises', function (done) { const gnr = new Band({ name: "Guns N' Roses", members: ['Axl', 'Slash'] });
const promise = gnr.save(); assert.ok(promise instanceof Promise);
promise.then(function (doc) { assert.equal(doc.name, "Guns N' Roses"); // acquit:ignore:start done(); // acquit:ignore:end }); });
/** * [Mongoose queries](http://mongoosejs.com/docs/queries.html) are **not** promises. They have a `.then()` * function for [co](https://www.npmjs.com/package/co) and async/await as * a convenience. If you need * a fully-fledged promise, use the `.exec()` function. */ it('Queries are not promises', function (done) { const query = Band.findOne({name: "Guns N' Roses"}); assert.ok(!(query instanceof Promise));
// acquit:ignore:start let outstanding = 2; // acquit:ignore:end
// A query is not a fully-fledged promise, but it does have a `.then()`. query.then(function(doc) { // use doc // acquit:ignore:start assert.ok(!doc); --outstanding || done(); // acquit:ignore:end });
// `.exec()` gives you a fully-fledged promise const promise = Band.findOne({name: "Guns N' Roses"}).exec(); assert.ok(promise instanceof Promise);
promise.then(function (doc) { // use doc // acquit:ignore:start assert.ok(!doc); --outstanding || done(); // acquit:ignore:end }); });
/** * Although queries are not promises, queries are [thenables](https://promisesaplus.com/#terminology). * That means they have a `.then()` function, so you can use queries as promises with either * promise chaining or [async await](https://asyncawait.net) */ it('Queries are thenable', function (done) { Band.findOne({name: "Guns N' Roses"}).then(function(doc) { // use doc // acquit:ignore:start assert.ok(!doc); done(); // acquit:ignore:end }); });
/** * There are two alternatives for using `await` with queries: * * - `await Band.findOne();` * - `await Band.findOne().exec();` * * As far as functionality is concerned, these two are equivalent. * However, we recommend using `.exec()` because that gives you * better stack traces. */ it('Should You Use `exec()` With `await`?', async function() { const doc = await Band.findOne({ name: "Guns N' Roses" }); // works // acquit:ignore:start assert.ok(!doc); // acquit:ignore:end
const badId = 'this is not a valid id'; try { await Band.findOne({ _id: badId }); } catch (err) { // Without `exec()`, the stack trace does **not** include the // calling code. Below is the stack trace: // // CastError: Cast to ObjectId failed for value "this is not a valid id" at path "_id" for model "band-promises" // at new CastError (/app/node_modules/mongoose/lib/error/cast.js:29:11) // at model.Query.exec (/app/node_modules/mongoose/lib/query.js:4331:21) // at model.Query.Query.then (/app/node_modules/mongoose/lib/query.js:4423:15) // at process._tickCallback (internal/process/next_tick.js:68:7) err.stack; // acquit:ignore:start assert.ok(!err.stack.includes('promises.test.js')); // acquit:ignore:end }
try { await Band.findOne({ _id: badId }).exec(); } catch (err) { // With `exec()`, the stack trace includes where in your code you // called `exec()`. Below is the stack trace: // // CastError: Cast to ObjectId failed for value "this is not a valid id" at path "_id" for model "band-promises" // at new CastError (/app/node_modules/mongoose/lib/error/cast.js:29:11) // at model.Query.exec (/app/node_modules/mongoose/lib/query.js:4331:21) // at Context.<anonymous> (/app/test/index.test.js:138:42) // at process._tickCallback (internal/process/next_tick.js:68:7) err.stack; // acquit:ignore:start assert.ok(err.stack.includes('promises.test.js')); // acquit:ignore:end } }); /** * If you're an advanced user, you may want to plug in your own promise * library like [bluebird](https://www.npmjs.com/package/bluebird). Just set * `mongoose.Promise` to your favorite * ES6-style promise constructor and mongoose will use it. */ it('Plugging in your own Promises Library', function (done) { // acquit:ignore:start if (!global.Promise) { return done(); } // acquit:ignore:end // Use bluebird mongoose.Promise = require('bluebird'); const bluebirdPromise = Band.findOne({name: "Guns N' Roses"}).exec(); assert.equal(bluebirdPromise.constructor, require('bluebird'));
// Use q. Note that you **must** use `require('q').Promise`. mongoose.Promise = require('q').Promise; const qPromise = Band.findOne({name: "Guns N' Roses"}).exec(); assert.ok(qPromise instanceof require('q').makePromise);
// acquit:ignore:start // Wait for promises bluebirdPromise.then(qPromise).then(function () { done(); }); // acquit:ignore:end });});
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