Skip to content

Obtaining deferred namespace imports #119

@guybedford

Description

@guybedford

The deferred evaluation proposal (https://github.com/tc39/proposal-defer-import-eval) is at Stage 3 in TC39 and starting to be implemented now.

We naturally support this in the ESM integration for deferring WebAssembly evaluation as already tracked in #101, but what we do not support is obtaining access to deferred JS namespaces.

This means that WebAssembly cannot import other modules in a way that indicates their execution should be deferred, like JS will be able to do.

The reason for this is that WebAssembly has no way to get the JS module namespace object itself currently as it only imports named exports directly.

For the ESM integration only, the strawman proposal here is to support an import convention form that can be used to obtain the JS module namespace object:

(import "./mod.js" "wasm-js:namespace" (global $ns externref))
(import "./mod.js" "wasm-js:deferred-namespace" (global $ns externref))

In ECMA-262 this directly corresponds to the fact that ~namespace~ and ~deferred-namespace~ are already specified as being supported through the ResolveExport path on the module record, so that we are using the export name position for the convention is not purely a hack, but also matches the underlying specification semantics (see https://tc39.es/proposal-defer-import-eval/#abstract-resolveexport).

Metadata

Metadata

Assignees

No one assigned

    Labels

    No labels
    No labels

    Type

    No type

    Projects

    No projects

    Milestone

    No milestone

    Relationships

    None yet

    Development

    No branches or pull requests

    Issue actions