Mixing named exports and re-exports in Babel

[just-boris]

This code transpiled by Babel does not detect the re-export:

export {named} from './named';
export * from './re-export';

Looking at the test-cases I see that this re-export alone is supported:

exports.__esModule = true;

var _reExport = require("./re-export");

Object.keys(_reExport).forEach(function (key) {
  if (key === "default" || key === "__esModule") return;
  if (key in exports && exports[key] === _reExport[key]) return;
  exports[key] = _reExport[key];
});

The code above correctly detects ./re-export. However, adding an extra named export changes the output slightly

exports.__esModule = true;
var _exportNames = {
  named: true
};
exports.named = void 0;

var _named = require("./named");

exports.named = _named.named;

var _reExport = require("./re-export");

Object.keys(_reExport).forEach(function (key) {
  if (key === "default" || key === "__esModule") return;
  if (Object.prototype.hasOwnProperty.call(_exportNames, key)) return;
  if (key in exports && exports[key] === _reExport[key]) return;
  exports[key] = _reExport[key];
});

Link to the Babel playground.

Runing this code through the lexer returns { exports: [ '__esModule', 'named' ], reexports: [] }, ./re-export was not detected

[guybedford]

Thanks @just-boris for posting, yes we should definitely support these cases, and ideally aim to get this upstreamed before the coming April releases if possible.

@nicolo-ribaudo seems I missed this one - wondering if there might be other scenarios I might have missed as well with the Babel output, now would be a good time to check if you're able to assist.

[nicolo-ribaudo]

I'm not able to check until Thursday, but I could try setting up an automated script that checks that Babel's fixtures work with this package.

[guybedford]

@nicolo-ribaudo that sounds very useful to me. As I say we have a milestone coming up with April so would be a good time to ship any fixes this month already if possible. It might be too late for Node.js 12 but we can at least catch Node.js 14+.

[guybedford]

(I'll make sure to allocate some time to this myself in the coming week or so too)

[nicolo-ribaudo]

@guybedford I created https://github.com/nicolo-ribaudo/validate-cjs-module-lexer, which compares the output of cjs-module-lexer with the ESM AST for Babel's fixtures (https://github.com/babel/babel/tree/main/packages/babel-plugin-transform-modules-commonjs/test/fixtures).

This is the current output

OK auxiliary comment / overview
OK class properties / live rewrite
OK class properties / private
OK class properties / private method
OK class properties / public
OK disable strict mode / strictMode false
FAIL interop / export all
	Expected values to be strictly deep-equal:
	+ actual - expected

	  {
	    exports: [
	      'default'
	    ],
	+   reexports: []
	-   reexports: [
	-     'react'
	-   ]
	  }
OK interop / export default
OK interop / export default 10
OK interop / export default 11
OK interop / export default 2
OK interop / export default 3
OK interop / export default 4
OK interop / export default 5
OK interop / export default 6
OK interop / export default 7
OK interop / export default 8
OK interop / export default 9
OK interop / export destructured
OK interop / export from
OK interop / export from 2
OK interop / export from 3
OK interop / export from 4
OK interop / export from 5
OK interop / export from 6
OK interop / export from 7
OK interop / export from 8
OK interop / export named
OK interop / export named 2
OK interop / export named 3
OK interop / export named 4
OK interop / export named 5
OK interop / exports variable
OK interop / hoist function exports
OK interop / illegal export esmodule
OK interop / illegal export esmodule 2
OK interop / imports
OK interop / imports default
OK interop / imports glob
OK interop / imports hoisting
OK interop / imports mixing
OK interop / imports named
OK interop / imports ordering
OK interop / module shadow
OK interop / multi load
OK interop / overview
OK interop / remap
OK interop loose / export default
OK interop loose / export default 10
OK interop loose / export default 11
OK interop loose / export default 2
OK interop loose / export default 3
OK interop loose / export default 4
OK interop loose / export default 5
OK interop loose / export default 6
OK interop loose / export default 7
OK interop loose / export default 8
OK interop loose / export default 9
OK interop loose / export destructured
OK interop loose / export from
OK interop loose / export from 2
OK interop loose / export from 3
OK interop loose / export from 4
OK interop loose / export from 5
OK interop loose / export from 6
OK interop loose / export from 7
OK interop loose / export from 8
OK interop loose / export named
OK interop loose / export named 2
OK interop loose / export named 3
OK interop loose / export named 4
OK interop loose / export named 5
OK interop loose / exports variable
OK interop loose / hoist function exports
OK interop loose / illegal export esmodule
OK interop loose / illegal export esmodule 2
OK interop loose / imports
OK interop loose / imports default
OK interop loose / imports glob
OK interop loose / imports hoisting
OK interop loose / imports mixing
OK interop loose / imports named
OK interop loose / imports ordering
OK interop loose / module shadow
OK interop loose / multi load
OK interop loose / overview
OK interop loose / remap
FAIL interop module string names / export from
	Expected values to be strictly deep-equal:
	+ actual - expected

	  {
	+   exports: [],
	-   exports: [
	-     'some exports'
	-   ],
	    reexports: []
	  }
FAIL interop module string names / export from string
	Expected values to be strictly deep-equal:
	+ actual - expected

	  {
	+   exports: [],
	-   exports: [
	-     'some exports'
	-   ],
	    reexports: []
	  }
FAIL interop module string names / export from string as string
	Expected values to be strictly deep-equal:
	+ actual - expected

	  {
	+   exports: [],
	-   exports: [
	-     'some exports'
	-   ],
	    reexports: []
	  }
FAIL interop module string names / export named
	Expected values to be strictly deep-equal:
	+ actual - expected

	  {
	    exports: [
	      'bar',
	-     'default exports'
	    ],
	    reexports: []
	  }
OK interop module string names / export named string can be identifier
OK interop module string names / import named
OK interop module string names / import named string can be identifier
FAIL interop module string names loose / export from
	Expected values to be strictly deep-equal:
	+ actual - expected

	  {
	+   exports: [],
	-   exports: [
	-     'some exports'
	-   ],
	    reexports: []
	  }
FAIL interop module string names loose / export from string
	Expected values to be strictly deep-equal:
	+ actual - expected

	  {
	+   exports: [],
	-   exports: [
	-     'some exports'
	-   ],
	    reexports: []
	  }
FAIL interop module string names loose / export from string as string
	Expected values to be strictly deep-equal:
	+ actual - expected

	  {
	+   exports: [],
	-   exports: [
	-     'some exports'
	-   ],
	    reexports: []
	  }
FAIL interop module string names loose / export named
	Expected values to be strictly deep-equal:
	+ actual - expected

	  {
	    exports: [
	      'bar',
	-     'default exports'
	    ],
	    reexports: []
	  }
OK interop module string names loose / export named string can be identifier
OK interop module string names loose / import named
OK interop module string names loose / import named string can be identifier
OK lazy dep / import default
OK lazy dep / import named
OK lazy dep / import namespace
OK lazy dep / reexport all
FAIL lazy dep / reexport default
	Expected values to be strictly deep-equal:
	+ actual - expected

	  {
	+   exports: [],
	-   exports: [
	-     'default'
	-   ],
	    reexports: []
	  }
FAIL lazy dep / reexport named
	Expected values to be strictly deep-equal:
	+ actual - expected

	  {
	+   exports: [],
	-   exports: [
	-     'named'
	-   ],
	    reexports: []
	  }
FAIL lazy dep / reexport namespace
	Expected values to be strictly deep-equal:
	+ actual - expected

	  {
	+   exports: [],
	-   exports: [
	-     'namespace'
	-   ],
	    reexports: []
	  }
OK lazy dep / sideeffect
OK lazy local / import default
OK lazy local / import named
OK lazy local / import namespace
OK lazy local / reexport all
OK lazy local / reexport default
OK lazy local / reexport named
OK lazy local / reexport namespace
OK lazy local / sideeffect
OK lazy whitelist / import default
OK lazy whitelist / import named
OK lazy whitelist / import namespace
OK lazy whitelist / reexport all
FAIL lazy whitelist / reexport default
	Expected values to be strictly deep-equal:
	+ actual - expected

	  {
	+   exports: [],
	-   exports: [
	-     'default'
	-   ],
	    reexports: []
	  }
FAIL lazy whitelist / reexport named
	Expected values to be strictly deep-equal:
	+ actual - expected

	  {
	    exports: [
	-     'named1',
	      'named2'
	    ],
	    reexports: []
	  }
FAIL lazy whitelist / reexport namespace
	Expected values to be strictly deep-equal:
	+ actual - expected

	  {
	    exports: [
	-     'namespace1',
	      'namespace2'
	    ],
	    reexports: []
	  }
OK lazy whitelist / sideeffect
OK misc / class static block
OK misc / copy getters setters
OK misc / copy getters setters star
OK misc / for of in export
OK misc / import const throw
OK misc / import shadowed assign
OK misc / local exports decl
OK misc / module exports
OK misc / reference source map
OK misc / undefined this arrow function
OK misc / undefined this computed class method 1
OK misc / undefined this computed class method 2
OK misc / undefined this computed class method 3
OK misc / undefined this computed class property name
OK misc / undefined this root call
OK misc / undefined this root declaration
OK misc / undefined this root reference
OK noInterop / export from
OK noInterop / import default only
OK noInterop / import wildcard
OK regression / 4462 T7565
OK regression / T7160
OK regression / T7165
OK regression / T7199
OK regression / T7272
OK regression / es3 compatibility
OK regression / es3 compatibility class
OK regression / es3 compatibility function
OK regression / es3 compatibility named class
OK regression / es3 compatibility named function
OK regression / issue 9155
OK regression / issue 9611
OK regression / lazy 7176
OK source map / exec
OK strict / export
OK strict / export 1
OK strict / export 2
OK strict / export 3
FAIL strict / export all
	Expected values to be strictly deep-equal:
	+ actual - expected ... Lines skipped

	  {
	    exports: [
	...
	      'z'
	    ],
	+   reexports: []
	-   reexports: [
	-     'mod'
	-   ]
	  }
OK strict / export const destructuring array
OK strict / export const destructuring array default params
OK strict / export const destructuring array rest
OK strict / export const destructuring deep
OK strict / export const destructuring object
OK strict / export const destructuring object default params
OK strict / export const destructuring object rest
OK strict / import
OK strict / import wildcard
OK update expression / negative suffix
OK update expression / positive suffix

[guybedford]

@nicolo-ribaudo thanks for checking these thoroughly, putting these on my list and hopefully will be able to tackle some next month.

[nicolo-ribaudo]

@guybedford I can work on this.

Note that all the other failures are not actually a problem because:

1. Node.js doesn't support string import names
2. The "lazy" tests are not Babel's default output, but an advanced option