Additonal export-from statements in ES7

The export ___ from "module" statements are a very useful mechanism for building up "package" modules in a declarative way. In the ES6 spec, we can:

• export through a single export with export {x} from "mod"
• ...optionally renaming it with export {x as v} from "mod"
• We can also spread all exports with export * from "mod".

These three export-from statements are easy to understand if you understand the semantics of the similar looking import statements.

However, there are other import statements which would have very useful export-from forms.

• Forwarding the default export of the referenced module as a named export of this module: export v from "mod"
• Exporting the ModuleNameSpace object as a named export: export * as ns from "mod"

Current ES6 Modules:

Proposed additions:

Common relationship between import and export

There's a common pattern of the export-from statements in that they mirror a similar import statement, but with the only difference being not altering local scope.

As an example:

export {v} from "mod";

Is very similar to:

import {v} from "mod";
export {v};

However, v is not introduced as a name in the local scope.

The two proposed additions follow this same pattern:

// proposed: export v from "mod"; 
import v from "mod";
export {v};

// proposed: export * as ns from "mod"; 
import * as ns from "mod";
export {ns};

Using the terminology of Table 42, the export-from form can be created from the import-then-export form by setting export-from's [[ExportName]] to import's [[LocalName]] and export-from's [[LocalName]] to null.

Table showing relationship