Add wasm_bindgen(skip) attribute

[alexlapa]

Resolves #1284.
Previous PR #1316 (closed).

Adds wasm_bindgen(skip) attribute to disable public fields exposure to JS.

Renamed attribute from 'ignore' to 'skip' according to @LegNeato's consideration to align naming with serde's #[serde(skip)].

[alexcrichton]

Awesome, thanks for this!

Could you also add some documentation to the reference in guide/src/reference?

[alexlapa]

@alexcrichton ,

Could you also add some documentation to the reference in guide/src/reference?

Done.

[alexcrichton]

Thanks!

[Sayan751]

It seems that this attribute only works for struct fields. I think it also makes sense to enable application of this attribute for methods. I would expect when this attribute is applied to a method, it is ignored by wasm-bindgen. For example, it will let me write something like this:

impl MyStruct {

  #[wasm_bindgen(skip)]
  pub fn my_method() -> &str {
    //...
  }

}

The advantage being is that then I can keep all the methods, both exposed to WASM as well as to other Rust libs, inside a single impl block. This in turn generates nicer docs, by putting all methods inside a single impl block, w/o any superfluous section.

What you guys think?

[alexcrichton]

Seems reasonable to me!

[emccorson]

It seems that this attribute only works for struct fields. I think it also makes sense to enable application of this attribute for methods

@Sayan751 Do you know if this was ever implemented? I was surprised to find skip doesn't work on methods and I came across this old issue.