memfs breaks with fs-extra^10.0.0

[Phillip9587]

memfs does not export fs.realpath.native. It is available since Node.js 9.2.0. https://nodejs.org/api/fs.html#fsrealpathnativepath-options-callback

fs-extra uses univeralify to create a promise version of fs.realpath.native. Because memfs does not provide it, universalify throws a error:

TypeError: Cannot read properties of undefined (reading 'name')

      at Object.<anonymous>.exports.fromCallback (../../node_modules/fs-extra/node_modules/universalify/index.js:15:26)
      at Object.<anonymous> (../../node_modules/fs-extra/lib/fs/index.js:57:27)
      at Object.<anonymous> (../../node_modules/fs-extra/lib/index.js:5:6)

The error occurs even if realpath.native is not used.

The line of code: https://github.com/jprichardson/node-fs-extra/blob/a84ef6dd8969f57d16e23267e1790def791e9a82/lib/fs/index.js#L57

[Phillip9587]

This is related to https://github.com/jprichardson/node-fs-extra/pull/887

[lamweili]

While https://github.com/jprichardson/node-fs-extra/pull/953 might address this such that fs-extra doesn't fail on import, memfs should still properly export fs.realpath.native.

Putting in simply, without fs-extra, if one actually used fs.realpath.native in their code, they would still have a problem due to memfs (or its underlying dependencies).

[G-Rath]

PRs are always welcome :)

[lamweili]

@G-Rath, assuming it's not a NodeJS <9.2.0 issue, I am unable to replicate it using NodeJS 14 with memfs@^3.4.1.

const assert = require('assert');
const memfs = require('memfs'); // memfs@^3.4.1

assert(typeof fs.realpath.native === 'function'); // is fine, not undefined

const fse = require('fs-extra'); // fs-extra@^10.0.1 - is fine, no errors as claimed

Might need more details from @Phillip9587. It is also possible to be an inherent nx behaviour that altered fs but reported wrongly as https://github.com/nrwl/nx/pull/8531.

[lamweili]

@Phillip9587, can you do a console.log(typeof fs.realpath.native) at the following 4 places?

1. the very first line of code
2. just before your nx import (I'm not familiar with this)
3. just before your memfs import
4. just before your fs-extra import

That would help to determine the underlying cause, if its environmental issues, or narrow down to a specific dependency (in-between) that has monkey-patched fs, causing fs-realpath.native to be undefined somewhat.

You might want to check the runtime NodeJS version through console.log(process.version).

[Phillip9587]

@peteriman I'm gonna look into it on monday. Hope it was no wrong report from my side.

[lamweili]

@Phillip9587 Any findings so far?

Nevertheless, it is likely related to fs.realpath.native being undefined, causing import of [email protected] to throw error.

Defensively patched in https://github.com/jprichardson/node-fs-extra/pull/953 and released in [email protected].

But still, why is fs.realpath.native undefined? That is a root cause to be investigated.

[G-Rath]

Has anyone been able to reproduce this on Node 14 or 16, using the latest version?

[lamweili]

I am unable to replicate it using NodeJS 14 with [email protected].

// pre-req
console.log(fs.realpath.native);
> [Function (anonymous)]

// memfs test
const memfs = require('memfs');
console.log(fs.realpath.native);
> [Function (anonymous)]

My suspicion is with nx (or other dependencies that altered fs). It might not be a memfs issue to begin with. Would need clarification from @Phillip9587.

[Phillip9587]

@peteriman Sorry for my late reply. The error originally ocurred after updating from fs-extra 9 to 10 in the Nx repo. The unit tests which used memfs were failing due to the error above. I looked into it and nx does not patch any fs methods so it was definitly related to memfs or/and fs-extra. But as you said the fs-extra 10.1.0 release fixes my issue ....

I think your test is wrong. I tested on Nodejs 16.15.0 and got the following:

// pre-req
const nodefs = require('fs');
console.log(nodefs.realpath.native);
> [Function (anonymous)]

// memfs test
const { fs } = require('memfs');
console.log(fs.realpath.native);
> undefined

I don't have any time to investigate further I'm sorry....

[Phillip9587]

@peteriman memfs 3.4.1

[lamweili]

@Phillip9587 Ah, thanks for that! I didn't assign it to the fs variable in my code, my bad!

---

@G-Rath I tested @Phillip9587's code snippet. It happens on [email protected] - 3.4.3 with NodeJS 14 and 16.

If memfs is imported to the fs variable name (as in the readme), it does not export fs.realpath.native:

// pre-req
const nodefs = require('fs');
console.log(nodefs.realpath.native);
> [Function (anonymous)]

// memfs test
const { fs } = require('memfs');
console.log(fs.realpath.native);
> undefined

Might be related to the under-the-hood dependency, fs-monkey.

[Phillip9587]

Defensively patched in https://github.com/jprichardson/node-fs-extra/pull/953 and released in [email protected].