WIP: named: commonjs exports

[vikr01]

This + #1222 closes #1145

This adds a new schema to named:

commonjs: boolean | { require: boolean, exports: boolean }

The option commonjs accepts either a boolean or a shape with require and exports booleans within. Defaults to false.

The reason why the shape is allowed is to avoid having commonjs require statements linted. Using the boolean only option will apply to both require and exports.

The following cases of assigning exports are checked:

Object.defineProperty(exports, "key", { value: "myValue" });
Object.defineProperty(module.exports, "key", { value: "myValue" });
Object.defineProperty(module["exports"], "key", { value: "myValue" });
Object.defineProperty(exports, "key", { "value": "myValue" });
Object.defineProperty(module.exports, "key", { "value": "myValue" });
Object.defineProperty(module["exports"], "key", { "value": "myValue" });

exports = {...};
module.exports = {...};
module["exports"] = {...};

exports.key = ...;
module.exports.key = ...;
module["exports"].key = ....;

All declarations must be at the top level. For example, this will not be checked:

if (foo) {
  exports.foo = foo;
}

The reason why we check Object.defineProperty is that babel will build es6 modules that way, i.e.:

Object.defineProperty(exports, "__esModule", { value: true });

We need to handle those (truthy) __esModule properties correctly -- as in the default export will be the entire module.exports if that's not set.

ExportMap.for and ExportMap.parse now take an options parameter (defaults to {}), with the keys useCommonjsExports and noInterop. Reason for noInterop is that plain require statements should not have .default being the entire module.exports if it doesn't have a truthy __esModule value.

TODO: Configure for babel-plugin-add-module-exports built files. (Check for module.exports = exports["default"] at the end.)

[coveralls]

Coverage decreased (-1.2%) to 96.195% when pulling 322d11e on vikr01:commonjs-named-exports into db471a8 on benmosher:master.

[benmosher]

Ah cool! It actually used to do this back in v0.x or v1, but I removed it for efficiency and to narrow the scope. I will have to think about this carefully before reintroducing.

[edi9999]

+1 on this "feature", I mostly use exports like this

module.exports = {
   foo: true,
   ...
}

and it is annoying that I have some unnoticed wrong imports.