Load CJS instead of ESM

[rtritto]

Description

Instance of parsed ObjectId, using ejson-shell-parser (version >= 1.2.1), is different from bson.ObjectId instance (bson version >= 5.0.0-alpha.0).
Correctly work:

• CommonJS (type: commonjs) with bson v4 and v5
• ESM (type: module) with bson v4

Same problem with Timestamp, BSONSymbol, DBRef, MinKey, MaxKey.

Steps to reproduce:

• yarn init -y
• yarn set version canary
• yarn add bson ejson-shell-parser
• Add "type": "module" in pakcage.json
• Create index.js file

import { ObjectId } from 'bson' 
import parser from 'ejson-shell-parser'
const out = parser.default('ObjectId()')
console.log(out instanceof ObjectId)

• yarn node index.js

Versions:

bson >= 5.0.0-alpha.0
ejson-shell-parser >= 1.2.1
Node: 16.17.0

Actual

log is false

Expect

log is true

[rtritto]

const out = parser.default('ObjectId()')
console.log(out instanceof ObjectId)  // false, should be true
console.log(typeof out)  // object
console.log(out.constructor.name)  // ObjectId

const outBson = new ObjectId()
console.log(outBson instanceof ObjectId)  // true
console.log(typeof outBson)  // object
console.log(outBson.constructor.name)  // ObjectId

console.log(typeof out === typeof outBson)  // true
console.log(out.constructor.name === outBson.constructor.name)  // true

[rtritto]

Implementation of instanceof:

function instanceOf(object, constructor) {
    while (object !== null) {
        if (object === constructor.prototype) {  //object is instanceof constructor
            return true
        } else if (typeof object === 'xml') {  //workaround for XML objects
            return constructor.prototype == XML.prototype
        }
        object = object.__proto__  //traverse the prototype chain
    }
    return false  //object is not instanceof constructor
}

Related problem:

console.log(out.__proto__ === ObjectId.prototype)  // false, should be true
console.log(outBson.__proto__ === ObjectId.prototype)  // true

Imply:

console.log(out.__proto__ === outBson.__proto__)  // false, should be true

[addaleax]

This just seems to be happening because ejson-shell-parser is loading the CommonJS version of bson and you are importing the ESM version of bson.

It’s expected that these are different. You can fix this by manually loading the CommonJS version from your code as well (if you ensure that the package gets deduplicated during yarn/npm install).

Generally speaking, this package doesn’t make guarantees about the specific prototypes that its returned values have; it only returns bson objects from a bson@5.x version.

[rtritto]

Can I do a PR to covert this to ESM?

Edit:
Maybe it's not needed because dist/ejson-shell-parser.esm.js in package.json

[rtritto]

ejson-shell-parser should use ESM ~ dist/ejson-shell-parser.esm.js (source package.json), so why?

[rtritto]

@addaleax I imported the ESM version (removing default from parse function) and it works.

import { ObjectId } from 'bson' 
import parser from './ejson-shell-parser.esm.js'  // same as file in dist folder
const out = parser('ObjectId()')
console.log(out instanceof ObjectId)  // output is true

I can confirm that ejson-shell-parser is imported as CJS instead of ESM.
How can ESM be correctly imported?

Edit:

This can be fixed using *.esm.mjs with dual package

Diff in package.json:

-   "main": "dist/ejson-shell-parser.cjs.js",
+   "main": "dist/ejson-shell-parser.cjs",
-   "module": "dist/ejson-shell-parser.esm.js",
+   "module": "dist/ejson-shell-parser.mjs",
...
+   "exports": {
+     "import": "./dist/ejson-shell-parser.mjs",
+     "require": "./dist/ejson-shell-parser.cjs"
+   }

import { ObjectId } from 'bson' 
import parser from 'ejson-shell-parser.esm.js'
const out = parser('ObjectId()')
console.log(out instanceof ObjectId)  // output is true

I opened preconstruct/preconstruct#576