feat(volume): support the recursive option for fs.watch()

[alienzhou]

The fs.watch API has recursive option but it did not implement it. For example, the watching listener below will not be triggered:

const vol = new Volume();
vol.mkdirSync('/test');

vol.watch('/', { recursive: true }, (eventType, filename) => {
  // won't be triggered
  console.log('fs.watch', eventType, filename);
});

setTimeout(() => {
  vol.writeFileSync('/test/lol.txt', '2');
}, 1000);

---

Besides when a child file's content (not recursive) is changed, the listener will not be triggered too:

const vol = new Volume();
vol.mkdirSync('/test');
vol.writeFileSync('/test/lol.txt', 'foo')

vol.watch('/test', { recursive: false }, (eventType, filename) => {
  // won't be triggered
  console.log('fs.watch', eventType, filename);
});

setTimeout(() => {
  vol.writeFileSync('/test/lol.txt', 'bar');
}, 1000);

Resolves #883

[G-Rath]

Does this resolve #883 by chance?

[alienzhou]

Does this resolve #883 by chance?

Yes. I added a new test case for #883 just now.

[streamich]

🎉 This PR is included in version 3.5.0 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot 📦🚀

[G-Rath]

fyi this is causing the tests that were added as part of streamich/unionfs#557 in unionfs to fail - I'm not sure if that is because of a bug in this code, in unionfs, or in the test suite

[G-Rath]

I think this implementation is buggy

Running the test using the native file system results in the file watcher being called only once and with `foo.js` (instead of twice and with `/tmp/foo.js`)

import { Volume } from '../volume';

function sleep(millisec: number): Promise<void> {
  return new Promise<void>((resolve, reject) => {
    setTimeout(resolve, millisec);
  });
}

describe('volume', () => {
  it('should create a watcher', async () => {
    const ufs = require('fs');
    ufs.writeFileSync('/tmp/foo.js', 'hello test');

    const mockCallback = jest.fn();
    const writtenContent = 'hello world';
    const watcher = ufs.watch('/tmp/foo.js', mockCallback as any);

    try {
      ufs.writeFileSync('/tmp/foo.js', writtenContent);

      await sleep(3000);

      expect(mockCallback).toBeCalledTimes(2);
      expect(mockCallback).toBeCalledWith('change', '/tmp/foo.js');
    } finally {
      watcher.close();
    }
  });
});

Running the test with `memfs` _before_ this change results in the test passing

import { Volume } from '../volume';

function sleep(millisec: number): Promise<void> {
  return new Promise<void>((resolve, reject) => {
    setTimeout(resolve, millisec);
  });
}

describe('volume', () => {
  it('should create a watcher', async () => {
    const ufs = Volume.fromJSON({ '/tmp/foo.js': 'hello test' });
//    const ufs = require('fs');
    ufs.writeFileSync('/tmp/foo.js', 'hello test');

    const mockCallback = jest.fn();
    const writtenContent = 'hello world';
    const watcher = ufs.watch('/tmp/foo.js', mockCallback as any);

    try {
      ufs.writeFileSync('/tmp/foo.js', writtenContent);

      await sleep(3000);

      expect(mockCallback).toBeCalledTimes(2);
      expect(mockCallback).toBeCalledWith('change', '/tmp/foo.js');
    } finally {
      watcher.close();
    }
  });
});

Running the test with `memfs` _after_ this change results in the test failing as being called with an empty string twice

import { Volume } from '../volume';

function sleep(millisec: number): Promise<void> {
  return new Promise<void>((resolve, reject) => {
    setTimeout(resolve, millisec);
  });
}

describe('volume', () => {
  it('should create a watcher', async () => {
    const ufs = Volume.fromJSON({ '/tmp/foo.js': 'hello test' });
//    const ufs = require('fs');
    ufs.writeFileSync('/tmp/foo.js', 'hello test');

    const mockCallback = jest.fn();
    const writtenContent = 'hello world';
    const watcher = ufs.watch('/tmp/foo.js', mockCallback as any);

    try {
      ufs.writeFileSync('/tmp/foo.js', writtenContent);

      await sleep(3000);

      expect(mockCallback).toBeCalledTimes(2);
      expect(mockCallback).toBeCalledWith('change', '/tmp/foo.js');
    } finally {
      watcher.close();
    }
  });
});