Importing both named and default from same file not working.

[ASafaeirad]

bug report:
after upgrading to v7.0, ES6 import seems weird.
importing both named and default from file seems not working right.
named imports become undefined when adding default import on same file.

Input Code

import mongoose, {Schema} from 'mongoose';
console.log(Schema); // undefined

but it works when removing default import.

import {Schema} from 'mongoose';
console.log(Schema) // object

Babel/Babylon Configuration (.babelrc, package.json, cli command)

{"presets": ["@babel/preset-env"] }

Expected Behavior

import mongoose from 'mongoose';
import {Schema} from 'mongoose';
console.log(Schema); // object

Current Behavior

import mongoose from 'mongoose';
import {Schema} from 'mongoose';
console.log(Schema); // undefiend

Your Environment

software	version(s)
Babel	7.0.0-beta.32
node	9.2.0
npm	5.5.1
mongoose	4.13.5
Operating System	Win10-x64

Edit

it just happens with mongoose. but when i downgrade babel it fixed.

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[nicolo-ribaudo]

mongoose has only a default export, not named exports (which are the equivalent of doing module.exports.Schema = Schema):
https://github.com/Automattic/mongoose/blob/master/lib/index.js#L860

[ASafaeirad]

@nicolo-ribaudo Ok, but why import { Schema } from 'mongoose'; works?

[loganfsmyth]

Hmm, this is a pain. The mongoose module puts .Schema on the prototype of the module.exports object.

So if you only have a named export, we don't bother using our interopRequireWildcard helper, but if you include the default, we do. The helper ignores prototype properties on module.exports, but the non-helper cases does access them.

We can leave this open so we can track it, but my recommendation would absolutely be to do

import mongoose from 'mongoose';
console.log(mongoose.Schema);

when you need the schema. ES6 import statements are not destructuring statements. This behavior may yet change more for Babel 7, we haven't fully decided yet.

[nicolo-ribaudo]

I'm tempted to mark this as won't fix/by design, since module.exports = new Mongoose, which mongoose uses [1], is the equivalent of export default new Mongoose. Thus, import { Schema } from "mongoose" is wrong.

cc @vkarpov15 (I'm pinging you because by looking at mongoose's commits you are the main maintainer).
What do you think about this?

[1] https://github.com/Automattic/mongoose/blob/6da0c525f5ab080a78631278cdb0d7d435ca976d/lib/index.js#L863

[vkarpov15]

@nicolo-ribaudo I agree, statements like import * from 'mongoose' and import {model} from 'mongoose' do not work with mongoose because of how the lib is structured. I opened up an issue on the mongoose repo (Automattic/mongoose#5940) to make a note of this on the readme.