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fix(NODE-6367): enable mixed use of iteration APIs (#4234)
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@W-A-James
W-A-James committed Sep 12, 2024
1 parent 0c6dbad commit d63bf6f
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2 changes: 1 addition & 1 deletion src/cursor/abstract_cursor.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -309,7 +309,7 @@ export abstract class AbstractCursor<
return bufferedDocs;
}
async *[Symbol.asyncIterator](): AsyncGenerator<TSchema, void, void> {
if (this.isClosed) {
if (this.closed) {
return;
}

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344 changes: 344 additions & 0 deletions test/integration/crud/find_cursor_methods.test.js
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Original file line number Diff line number Diff line change
@@ -1,6 +1,7 @@
'use strict';
const { expect } = require('chai');
const { filterForCommands } = require('../shared');
const { promiseWithResolvers, MongoCursorExhaustedError } = require('../../mongodb');

describe('Find Cursor', function () {
let client;
Expand Down Expand Up @@ -361,4 +362,347 @@ describe('Find Cursor', function () {
}
});
});

describe('mixing iteration APIs', function () {
let client;
let collection;
let cursor;

beforeEach(async function () {
client = this.configuration.newClient();
await client.connect();
collection = client.db('next-symbolasynciterator').collection('bar');
await collection.deleteMany({}, { writeConcern: { w: 'majority' } });
await collection.insertMany([{ a: 1 }, { a: 2 }], { writeConcern: { w: 'majority' } });
});

afterEach(async function () {
await cursor.close();
await client.close();
});

context('when all documents are retrieved in the first batch', function () {
it('allows combining iteration modes', async function () {
let count = 0;
cursor = collection.find().map(doc => {
count++;
return doc;
});

await cursor.next();
// eslint-disable-next-line no-unused-vars
for await (const _ of cursor) {
/* empty */
}

expect(count).to.equal(2);
});

it('works with next + next() loop', async function () {
let count = 0;
cursor = collection.find().map(doc => {
count++;
return doc;
});

await cursor.next();

let doc;
while ((doc = (await cursor.next()) && doc != null)) {
/** empty */
}

expect(count).to.equal(2);
});

context('when next() is called in a loop after a single invocation', function () {
it('iterates over all documents', async function () {
let count = 0;
cursor = collection.find({}).map(doc => {
count++;
return doc;
});

await cursor.next();

let doc;
while ((doc = (await cursor.next()) && doc != null)) {
/** empty */
}

expect(count).to.equal(2);
});
});

context(
'when cursor.next() is called after cursor.stream() is partially iterated',
function () {
it('returns null', async function () {
cursor = collection.find({});

const stream = cursor.stream();
const { promise, resolve, reject } = promiseWithResolvers();

stream.once('data', v => {
resolve(v);
});

stream.once('error', v => {
reject(v);
});
await promise;

expect(await cursor.next()).to.be.null;
});
}
);

context('when cursor.tryNext() is called after cursor.stream()', function () {
it('returns null', async function () {
cursor = collection.find({});

const stream = cursor.stream();
const { promise, resolve, reject } = promiseWithResolvers();

stream.once('data', v => {
resolve(v);
});

stream.once('error', v => {
reject(v);
});
await promise;

expect(await cursor.tryNext()).to.be.null;
});
});

context(
'when cursor.[Symbol.asyncIterator] is called after cursor.stream() is partly iterated',
function () {
it('returns an empty iterator', async function () {
cursor = collection.find({});

const stream = cursor.stream();
const { promise, resolve, reject } = promiseWithResolvers();

stream.once('data', v => {
resolve(v);
});

stream.once('error', v => {
reject(v);
});
await promise;

let count = 0;
// eslint-disable-next-line no-unused-vars
for await (const _ of cursor) {
count++;
}

expect(count).to.equal(0);
});
}
);

context('when cursor.readBufferedDocuments() is called after cursor.next()', function () {
it('returns an array with remaining buffered documents', async function () {
cursor = collection.find({});

await cursor.next();
const docs = cursor.readBufferedDocuments();

expect(docs).to.have.lengthOf(1);
});
});

context('when cursor.next() is called after cursor.toArray()', function () {
it('returns null', async function () {
cursor = collection.find({});

await cursor.toArray();
expect(await cursor.next()).to.be.null;
});
});

context('when cursor.tryNext is called after cursor.toArray()', function () {
it('returns null', async function () {
cursor = collection.find({});

await cursor.toArray();
expect(await cursor.tryNext()).to.be.null;
});
});

context('when cursor.[Symbol.asyncIterator] is called after cursor.toArray()', function () {
it('should not iterate', async function () {
cursor = collection.find({});

await cursor.toArray();
// eslint-disable-next-line no-unused-vars
for await (const _ of cursor) {
expect.fail('should not iterate');
}
});
});

context('when cursor.readBufferedDocuments() is called after cursor.toArray()', function () {
it('return and empty array', async function () {
cursor = collection.find({});

await cursor.toArray();
expect(cursor.readBufferedDocuments()).to.have.lengthOf(0);
});
});

context('when cursor.stream() is called after cursor.toArray()', function () {
it('returns an empty stream', async function () {
cursor = collection.find({});
await cursor.toArray();

const s = cursor.stream();
const { promise, resolve, reject } = promiseWithResolvers();

s.once('data', d => {
reject(d);
});

s.once('end', d => {
resolve(d);
});

expect(await promise).to.be.undefined;
});
});
});

context('when there are documents that are not retrieved in the first batch', function () {
it('allows combining next() and for await syntax', async function () {
let count = 0;
cursor = collection.find({}, { batchSize: 1 }).map(doc => {
count++;
return doc;
});

await cursor.next();
// eslint-disable-next-line no-unused-vars
for await (const _ of cursor) {
/* empty */
}

expect(count).to.equal(2);
});

context(
'when a cursor is partially iterated with for await and then .next() is called',
function () {
it('throws a MongoCursorExhaustedError', async function () {
cursor = collection.find({}, { batchSize: 1 });

// eslint-disable-next-line no-unused-vars
for await (const _ of cursor) {
/* empty */
break;
}

const maybeError = await cursor.next().then(
() => null,
e => e
);
expect(maybeError).to.be.instanceof(MongoCursorExhaustedError);
});
}
);

context('when next() is called in a loop after a single invocation', function () {
it('iterates over all documents', async function () {
let count = 0;
cursor = collection.find({}, { batchSize: 1 }).map(doc => {
count++;
return doc;
});

await cursor.next();

let doc;
while ((doc = (await cursor.next()) && doc != null)) {
/** empty */
}

expect(count).to.equal(2);
});
});

context('when cursor.readBufferedDocuments() is called after cursor.next()', function () {
it('returns an empty array', async function () {
cursor = collection.find({}, { batchSize: 1 });

await cursor.next();
const docs = cursor.readBufferedDocuments();

expect(docs).to.have.lengthOf(0);
});
});

context('when cursor.next() is called after cursor.toArray()', function () {
it('returns null', async function () {
cursor = collection.find({}, { batchSize: 1 });

await cursor.toArray();
expect(await cursor.next()).to.be.null;
});
});

context('when cursor.tryNext is called after cursor.toArray()', function () {
it('returns null', async function () {
cursor = collection.find({}, { batchSize: 1 });

await cursor.toArray();
expect(await cursor.tryNext()).to.be.null;
});
});

context('when cursor.[Symbol.asyncIterator] is called after cursor.toArray()', function () {
it('should not iterate', async function () {
cursor = collection.find({}, { batchSize: 1 });

await cursor.toArray();
// eslint-disable-next-line no-unused-vars
for await (const _ of cursor) {
expect.fail('should not iterate');
}
});
});

context('when cursor.readBufferedDocuments() is called after cursor.toArray()', function () {
it('return and empty array', async function () {
cursor = collection.find({}, { batchSize: 1 });

await cursor.toArray();
expect(cursor.readBufferedDocuments()).to.have.lengthOf(0);
});
});

context('when cursor.stream() is called after cursor.toArray()', function () {
it('returns an empty stream', async function () {
cursor = collection.find({}, { batchSize: 1 });
await cursor.toArray();

const s = cursor.stream();
const { promise, resolve, reject } = promiseWithResolvers();

s.once('data', d => {
reject(d);
});

s.once('end', d => {
resolve(d);
});

expect(await promise).to.be.undefined;
});
});
});
});
});

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