Aliased symbol also exported under non-aliased name.

[mbostock]

index.js:

export {
  default as axis,
  orientBottom as axisOrientBottom
} from "./src/axis";

src/axis.js:

export var orientBottom = {name: "bottom"};

export default function() {
  var orient;

  function axis() {}

  axis.orient = function() {
    orient = orientBottom;
  };

  return axis;
};

Resulting Rollup with -f amd:

define(['exports'], function (exports) { 'use strict';

  exports.orientBottom = {name: "bottom"};

  function axis() {
    var orient;

    function axis() {}

    axis.orient = function() {
      orient = exports.orientBottom;
    };

    return axis;
  };

  exports.axis = axis;
  exports.axisOrientBottom = exports.orientBottom;

});

Note that the bottom orientation is unexpectedly exported twice: once as orientBottom (wrongly) and once as axisOrientBottom (correctly).

[mbostock]

Here’s an even simpler case for src/axis.js:

export var orientBottom = 42;

export default function() {
  var orient;
  orient = orientBottom;
};

Which produces:

define(['exports'], function (exports) { 'use strict';

  exports.orientBottom = 42;

  function axis() {
    var orient;
    orient = exports.orientBottom;
  };

  exports.axis = axis;
  exports.axisOrientBottom = exports.orientBottom;

});

[mbostock]

I can work around this issue by creating a var instead of an alias in index.js:

import {orientBottom} from "./src/axis";
export {default as axis} from "./src/axis";
export var axisOrientBottom = orientBottom;

I assume this has something to do with exports being bindings rather than constants. Like, it’s protecting against someone importing axisOrientBottom and the setting the value to something else, yeah?

[mbostock]

Another interesting observation is that it produces broken code if the exported symbol is a function. In src/axis.js:

export function orientBottom() {};

export default function() {
  var orient;
  orient = orientBottom;
};

Which produces:

define(['exports'], function (exports) { 'use strict';

  function exports.orientBottom() {};

  function axis() {
    var orient;
    orient = exports.orientBottom;
  };

  exports.axis = axis;
  exports.axisOrientBottom = exports.orientBottom;

});

Which then fails because “exports.orientBottom” isn’t a valid function name.

[mbostock]

Although as I understand it (per 2ality), the imported ES6 binding should be immutable: no one should be able to reassign the axisOrientBottom symbol outside of the module that defines it.

That can’t be strictly enforced by Rollup when converting to ES5 (unless you wanted to protect the exports with a getter/setter rather than using a dumb object, or using Object.freeze, neither of which I’d prefer due to compatibility reasons). But I don’t really care about preventing people from writing broken code. :)

[Rich-Harris]

Fixed at last, in 0.25.1 (the first bug, not the function exports.whatever one – tracking that in #454). Thanks