JS API: getters and setters (code migration)

[bvibber]

It seems that the JS projection of GC structs as JS Typed Objects adds a generic getter/setter for each field that accesses that field, but there's no provision for custom getters and setters (for instance to get a synthesized value, or to be alerted when a property is changed so other internal state can change).

These could be provided in JavaScript by modifying the prototype with custom JavaScript getter/setter functions, at the cost of not exposting the property as an "own property".

The getters/setters would need to be JavaScript according to current spec due to #153.

Would this be a problem for code migration of existing JS APIs that use properties with getters/setters or would this sort of workaround be enough to reach the spec's code migration goals?

[tlively]

We've decided that custom getters, setters, field accessors, methods, etc. should be considered in a post-MVP proposal: https://github.com/webassembly/gc-js-customization. For the MVP, code migration will have to depend on manually wrapping idiomatic APIs around exported functions.