Support for Maps

[markandrus]

Is it planned to support Maps or other JavaScript data types in wasm-bindgen? For example,
I would like to be able to bind a function that returns a BTreeMap<String, String> (unless there is a more appropriate type for maps—I'm relatively new to Rust).

[alexcrichton]

A good question! I think this is probably best done for now through something like #96 and the API would use JsValue, but would that still be too cumbersome?

[alexcrichton]

Ok I'm gonna close this in favor of #96 as I think that's probably the route we'd take for this, but thanks for the report!

[couchand]

I think it would be worth supporting the limited case of string to string maps. A handful of web APIs use them, for instance Headers and URLSearchParams.

[alexcrichton]

@couchand in both those cases though those are dedicated classes, right? I'd imagine we'd want native bindings to them and then perhaps a helper method to convert them to a map on the Rust side?

[couchand]

Unfortunately, I don't think dedicated classes would work there, since they have arbitrary keys.

[alexcrichton]

Ah if that's the case then yeah we may need to add some more support for more maps in the future as well!