The JsModuleEvaluation method always returns a result equal to undefined

[Taritsyn]

I am working on implementing support of the ECMAScript 2015 static modules in a .NET library (JavaScript Engine Switcher project). I've already read the API documentation and “Steps needed for es6 modules embedding ChakraCore” discussion.

But I have not found anywhere information about how to get the result of module evaluation. Suppose there is the following code of root module:

import * as geometry from './geometry/geometry.js';
new geometry.Square(15).area;

The expected result of evaluating this module is a numerical value equal to 225, but the JsModuleEvaluation method always returns undefined.

To make it easier for you to find the reason for this behavior, I created a .NET Core console application.

[rhuanjl]

I've done a bit of digging - the ability to get a result value via JsModuleEvaluation appears to be an untested feature (nothing in the test suite looks at it) that either never worked or if it did work it was broken a while ago.

As far as I can see it is not currently possible to retrieve a value from a module unless it's exported.

Currently in the release branches the result from JsModuleEvaluation will always be undefined in the master branch it will always be {done : true} neither is useful.

I will have a look at fixing this.

[Taritsyn]

Hello, Richard!

Thanks for quick response!

Currently in the release branches the result from JsModuleEvaluation will always be undefined in the master branch it will always be {done : true} neither is useful.

I do not know how standard this behavior is, but in the Microsoft ClearScript during evaluation of the similar code returns a numerical value.

I've done a bit of digging - the ability to get a result value via JsModuleEvaluation appears to be an untested feature (nothing in the test suite looks at it) that either never worked or if it did work it was broken a while ago.

Here I would like to receive a comment from @liminzhu.

[fatcerberus]

IIRC, as written in the ECMAScript specification, the module evaluation algorithm canonically returns a normal completion of undefined, so ChakraCore’s result here is correct.

The only thing you’re meant to be able to extract from a successfully evaluated ES module is its module namespace object (i.e. its export table).

[rhuanjl]

@fatcerberus if that's the case I should fix master to return undefined again - as there's no test of this return value I hadn't noticed that my work in #6171 changed it until this issue prompted me to look.

However the documentation of JsModuleEvaluation implies that it perhaps provides some kind of useful value - which it obviously doesn't.