Define ModuleNamespace to ECMA-262 Module Namespace Exotic Object

[guybedford]

This came up in a PR addition to the WebAssembly ESM Integration in WebAssembly/esm-integration#104 to have a WebIDL function definition returning a ModuleNamespace object (namespaceInstance below):

interface Instance {
  constructor(Module module, optional object importObject);
  readonly attribute object exports;
  static Instance namespaceInstance(ModuleNamespace moduleNamespace);
};

To support this it would be beneficial to have an upstream definition of ModuleNamespace to ensure validations are handled at the WebIDL layer for functions taking module namespaces as arguments.

The PR has not landed yet, posting this up for initial feedback before the ESM Integration PR lands.

• At least two implementers are interested (and none opposed):
  • …
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• Tests are written and can be reviewed and commented upon at:
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• Implementation bugs are filed:
  • Chromium: …
  • Gecko: …
  • WebKit: …
  • Deno: …
  • Node.js: …
  • webidl2.js: …
  • widlparser: …
• MDN issue is filed: …
• The top of this comment includes a clear commit message to use.

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[annevk]

This looks okay to me, but the template will have to be filled in. One caveat here I guess is that Wasm JS API bindings are not actually implemented through IDL in (most?) implementations.

[guybedford]

Thanks for taking a look and I believe you're right on the implementation aspects. The alternative would be to just use object and then to define the validations in line, but this seemed better if possible, unless you can see any reasons against having this defined here.

I'll aim to get the Node.js implementation together and post back the template with an update when that's ready.