Babel helper export is wrongly hoisted

[TrySound]

Is rollup able to code split inlined babel helpers?

I got an issue with this. This helper is exported at the top of the chunk with exports({ e: _extends })

var _extends = Object.assign || function (target) { for (var i = 1; i < arguments.length; i++) { var source = arguments[i]; for (var key in source) { if (http://Object.prototype.hasOwnProperty.call (source, key)) { target[key] = source[key]; } } } return target; };

I guess it's inlined helper. Babel distributes babe-runtime with not minified helpers.

Moving exports({}) to the bottom of the chunk should solve the problem.

And I don't know how to reproduce this in small sandbox.

[lukastaegert]

It would be nice to have a little more information.

• Which output format does this apply to?
• In which situations does this happen?
• Do you have a repo or test case that exposes the problem? Otherwise there is no way for us to determine if a fix is working and I hate to do guess-work here.

[TrySound]

It's systemjs. I don't know why, this happens when I add babel-plugin-transform-runtime.

As I said I don't know how to reproduce this with small sandbox. It fails only in my big app with special case. So I'm asking is rollup able to split consumed files in the middle?

My problem is splitted inlined helper which cannot hoist and considered by rollup as hoisted.

[TrySound]

@lukastaegert @guybedford I found how to reproduce bug. Not sure it's exactly same bug though.
https://github.com/TrySound/rollup-bug-1

[TrySound]

@lukastaegert This just broke my app completely and unconditionally today. I can only remove some pages to fix it. Really annoying problem.

[TrySound]

@lukastaegert I removed all plugins except commonjs. Hope this will simplify your investigation.

[guybedford]

@TrySound it may help if you can share the build output, and do as much as you can to cut down the size of the build by emptying all modules that aren't affecting the issue.

[TrySound]

@guybedford Reduced a lot. Take a look please if you have a time.

[TrySound]

(function () {
  'use strict';

  function _extends$1() {
    _extends$1 = Object.assign || function (target) {
      for (var i = 1; i < arguments.length; i++) {
        var source = arguments[i];

        for (var key in source) {
          if (Object.prototype.hasOwnProperty.call(source, key)) {
            target[key] = source[key];
          }
        }
      }

      return target;
    };

    return _extends$1.apply(this, arguments);
  }

  var whitelist = ['en', 'fr'];
  var versions = whitelist.reduce(function (acc, lng) {
    var _extends2;

    return _extends({}, acc, (_extends2 = {}, _extends2[lng] = null, _extends2));
  }, {});

}());

[lukastaegert]

Ok, so this looks like _extends is referenced as _extends$1 as if it has been deconflicted against itself.

[lukastaegert]

Reduced the repro as much as possible:
https://rollupjs.org/repl?version=0.66.5&shareable=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

There are actually several critical pieces to trigger this:

• There is a default export with an id that is actually used
• This id is reassigned in the same module
• There is a naming conflict that triggers this id to be deconflicted (it can also be a naming conflict with something that is eventually tree-shaken as in this example)

[lukastaegert]

It seems the issue is related to the fact that for the reassignment, a LocalVariable is used/introduced that is disconnected from the ExportDefaultvariable generated by the export.

[lukastaegert]

Will keep investigating tomorrow.

[TrySound]

Thanks. At least I found a way to fix the issue. I just overrode extends helpers in transform hook.

[lukastaegert]

Potential fix at #2502. Could you check if this also fixes the original issue?

[TrySound]

Just tried. Works perfectly. Thank you