Additional export-get statements

ES Proposal

Stage: undefined

Author: Caridy Patiño

Specification: TBD

AST: TBD

Transpiler: TBD.

Rationale

As part of the effort to make "Reflective Module Records" to fulfill most use-cases in Node to support inter-operatibility between CJS and ES Modules, we came across some CJS modules that were exporting a getter via Object.definedProperty().

Further investigation revealed that there is no way to have an equivalent ES Module. This proposal is aiming to fill that gap in the spec by introducing a declarative way to define an export getter.

Two new export statements will be needed to fulfill this use-case, the export get ___ () {} and export default get ___ () {} statements can export a computed value via a getter-like definition. This proposal attempts to re-use an existing grammatical form that is already well understood by the community:

let o = {
    get foo() {
        return "something";
    }
}

Proposed additions to Modules Export Statements

Export Statement Form	[[ModuleRequest]]	[[ImportName]]	[[LocalName]]	[[ExportName]]
export get foo() {}	null	null	"foo"	"foo"
export default get () {}	null	null	"*default*"	"*default*"
export default get foo() {}	null	null	"foo"	"*default*"

Examples

Exporting a default computed value via a getter:

let firstname = "Caridy";
let lastname  = "Patiño";
export default get () {
    return `${firstname} ${lastname}`;
}

CJS Equivalent:

let firstname = "Caridy";
let lastname = "Patiño";
Object.defineProperty(module, 'exports', {
    get: () => `${firstname} ${lastname}`
});

Exporting a computed value via a getter:

let firstname = "Caridy";
let lastname  = "Patiño";
export get fullname () {
    return `${firstname} ${lastname}`;
}

CJS Equivalent:

let firstname = "Caridy";
let lastname = "Patiño";
module.exports = {
    get fullname() {
        return `${firstname} ${lastname}`;
    }
};