Support custom documentation for setters

[mre]

Consider this builder:

custom_derive! {
    #[derive(Debug, Default, Builder)]
    struct Channel {
        //! This is a comment for token
        token: i32,
        special_info: i32
    }
}

It would be great if there was a way to add the comments as documentation for the fields:

//! This is a comment for token
fn token<VALUE: Into<i32>>(mut self, value: VALUE) -> Self {
    self.token = value.into();
    self
}

No clue if that is possible, though. 😄

[killercup]

This should be possible, /// hi there comments become #[doc="hi there"] attributes.

Would you want to differentiate between comments for the struct field and comments for the setter? (If the field is not public, its docs wouldn't be rendered, so it might be cool to just add them to the setter fn.)

[mre]

Thanks for the quick response.
Documentation for the setter would be enough for me right now. But a fallback for non-public fields would be totally awesome. Depends on how tricky it is to implement.

[colin-kiegel]

@mre thank you very much for your feedback. :-)

A simple solution would be to allow item doc-comments, but to skip over them and use auto-generated documentation for setters. Spontaneously that is what I would try first and then wait and see if there is a big need for something more sophisticated or magic.

[colin-kiegel]

Ok, for now we have auto-generated doc-comments (95f3b4b)

/// Set `$field_name`
///
/// auto-generated by [derive_builder](https://crates.io/crates/derive_builder)

Skipping doc-comments (and pub keywords) in the struct definition is a bit more delicate and therefore a pull request #14

I am open for future changes - but I think this is at least an improvement of the current state. I will release now without the pull request. ;-)

[colin-kiegel]

implemented and published with v0.2.0 (Changelog)