Proc_macro_roids 0.5.0 released

[azriel91]

proc_macro_roids

Traits and functions to make writing proc macros more ergonomic.

• crates.io
• repository
• docs.rs

Suppose you want to write a proc macro, that takes in this struct (example repo):

use std::marker::PhantomData;
use super_derive::Super;

#[derive(Super)]
pub struct Man<T> {
    #[super_derive(skip)]
    name: String,
    power_level: u64,
    marker: PhantomData<T>,
}

And generates this:

pub enum SuperMan {
    U64(u64),
}

Traversing the syntax tree is verbose, and writing error messages for each incorrect traversal is tedious.

With proc_macro_roids, the procedural macro code to implement the above is concise and expressive:

#[proc_macro_derive(Super, attributes(super_derive))]
pub fn system_desc_derive(input: TokenStream) -> TokenStream {
    let ast = parse_macro_input!(input as DeriveInput);
    let enum_name = ast.ident.prepend("Super");
    let fields = ast.fields();
    let relevant_fields = fields
        .iter()
        .filter(|field| !field.is_phantom_data())
        .filter(|field| !field.contains_tag(&parse_quote!(super_derive), &parse_quote!(skip)));

    let variants = relevant_fields
        .map(|field| {
            let type_name = field.type_name();
            let variant_name = type_name.to_string().to_uppercase();
            let variant_name = Ident::new(&variant_name, Span::call_site());
            quote! {
                #variant_name(#type_name)
            }
        })
        .collect::<Vec<_>>();

    let token_stream2 = quote! {
        pub enum #enum_name {
            #(#variants,)*
        }
    };

    token_stream2.into()
}

---

What's new:

0.5.0 (2019-08-19)

• syn, quote, and proc_macro2 are upgraded to 1.0.
• Breaking: nested_meta_to_ident is renamed to nested_meta_to_path.

0.4.0 (2019-08-17)

• Breaking: DeriveInputDeriveExt is renamed to DeriveInputExt.
• FieldExt::tag_parameter extracts the Meta param from #[namespace(tag(param))].
• FieldExt::tag_parameters extracts the Meta params from #[namespace(tag(param1, param2))].
• DeriveInputExt::tag_parameter extracts the Meta param from #[namespace(tag(param))].
• DeriveInputExt::tag_parameters extracts the Meta params from #[namespace(tag(param1, param2))].

0.3.0

• FieldExt provides methods to work with Fields:

  • contains_tag
  • is_phantom_data
  • type_name

[azriel91]

0.5.0 release uses 1.0 versions of syn, quote, and proc-macro2.

p/s: Update your proc macro crates dependencies too!