reflection_derive/src/lib.rs

#![recursion_limit="128"]

extern crate proc_macro;
extern crate syn;

extern crate serde_derive_internals;
use serde_derive_internals::attr::get_serde_meta_items;

use syn::Meta::{NameValue,Word};
use syn::NestedMeta::Meta;

#[macro_use]
extern crate quote;

use proc_macro::TokenStream;
use syn::{ DeriveInput, Data, Fields, Generics, GenericParam };
use quote::Tokens;

#[proc_macro_derive( Reflection )]
pub fn derive_reflection( input: TokenStream) -> TokenStream {
    let input: DeriveInput = syn::parse( input ).unwrap();
    let name = input.ident;
    let generics = add_trait_bounds( input.generics );
    let ( impl_generics, ty_generics, where_clause ) = generics.split_for_impl();
    let members = aggregate( &input.data );
    let schema = generate_schema( &input.data );
    let ty = generate_ty( &input.data );

    let expanded = quote! {
        impl #impl_generics ::reflection::Reflection for #name #ty_generics #where_clause {
            fn ty() -> ::reflection::Type { #ty }
            fn name() -> ::reflection::Name { Some( String::from( stringify!( #name )))}

            fn schema( id: ::reflection::Id ) -> ::reflection::Schema {
                let mut tree = {#schema};
                match &mut tree.root_mut().data {
                    ::reflection::Member::Field( ref mut field ) => {
                        field.id = id;
                        field.tyname = Self::name();
                        field.expander = Some( <#name #ty_generics as Reflection>::members );
                    },
                    ::reflection::Member::Variant( ref mut variant ) => {
                        variant.id = id;
                    },
                }
                tree
            }

            fn members() -> ::reflection::Schemas { #members }
        }
    };

    expanded.into()
}

fn add_trait_bounds( mut generics: Generics ) -> Generics {
    for param in &mut generics.params {
        if let GenericParam::Type( ref mut type_param ) = *param {
            let bound = syn::parse_str( "::reflection::Reflection" ).unwrap();
            type_param.bounds.push( bound );
        }
    }
    generics
}

fn is_skipped( attrs: &Vec<syn::Attribute> ) -> bool {
    for meta_items in attrs.iter().filter_map( get_serde_meta_items ) {
        for meta_item in meta_items {
            match meta_item {
                // Parse `#[serde(skip_serializing)]`
                Meta( Word( word )) if word == "skip_serializing" => {
                    return true
                }
                _ => continue
            }
        }
    }
    false
}

fn serde_rename( field: &syn::Field ) -> Option<String> {
    for meta_items in field.attrs.iter().filter_map( get_serde_meta_items ) {
        for meta_item in meta_items {
            match meta_item {
                // Parse `#[serde(rename = "foo")]`
                Meta( NameValue( ref m )) if m.ident == "rename" => {
                    if let syn::Lit::Str( ref lit ) = *&m.lit {
                        return Some( lit.value() )
                    }
                }
                _ => continue
            }
        }
    }
    None
}

fn generate_ty( data: &Data ) -> Tokens {
    match *data {
        Data::Struct(_) => {
            quote!( ::reflection::Type::Struct )
        }
        Data::Enum(_) => {
            quote!( ::reflection::Type::Enum )
        } 
        Data::Union(_) => unimplemented!()
    }
}

fn generate_schema( data: &Data ) -> Tokens {
    match *data {
        Data::Struct(_) => {
            quote!( ::reflection::field( "_", ::reflection::Type::Struct, None, None ))
        }
        Data::Enum(_) => {
            quote!( ::reflection::field( "_", ::reflection::Type::Enum, None, None ))
        } 
        Data::Union(_) => unimplemented!()
    }
}

fn aggregate( data: &Data ) -> Tokens {
    match *data {
        Data::Struct( ref data ) => {
            match data.fields {
                Fields::Named( ref fields ) => {
                    let fnames = fields.named.iter().filter( |f| !is_skipped( &f.attrs )).map( |f|
                        match serde_rename(f) {
                            Some( name ) => name,
                            None => f.ident.unwrap().to_string()
                        }
                    );
                    let ftypes1 = fields.named.iter().map( |f| f.ty.clone() );
                    let ftypes2 = fields.named.iter().map( |f| f.ty.clone() );
                    let ftypes3 = fields.named.iter().map( |f| f.ty.clone() );
                    quote! {
                        #(
                            -( ::reflection::field(
                                    #fnames,
                                    <#ftypes1 as ::reflection::Reflection>::ty(),
                                    <#ftypes2 as ::reflection::Reflection>::name(),
                                    Some( <#ftypes3 as ::reflection::Reflection>::members )))
                        )*
                    }
                }
                Fields::Unnamed( ref fields ) => {
                    let mut i = 0;
                    let indices = fields.unnamed.iter().filter( |f| !is_skipped( &f.attrs )).map( |f|
                        match serde_rename(f) {
                            Some( name ) => name,
                            None => { i += 1; return (i-1).to_string() }
                        }
                    );
                    let ftypes1 = fields.unnamed.iter().map( |f| f.ty.clone() );
                    let ftypes2 = fields.unnamed.iter().map( |f| f.ty.clone() );
                    let ftypes3 = fields.unnamed.iter().map( |f| f.ty.clone() );
                    quote! {
                        #(
                            -( ::reflection::field(
                                    #indices,
                                    <#ftypes1 as ::reflection::Reflection>::ty(),
                                    <#ftypes2 as ::reflection::Reflection>::name(),
                                    Some( <#ftypes3 as ::reflection::Reflection>::members )))
                        )*
                    }
                }
                Fields::Unit => {
                    quote!( ::reflection::Schemas::new() )
                }
            }
        }
        Data::Enum( ref data ) => {
            let vnames = data.variants.iter().map( |v| v.ident );

            let fnames = data.variants.iter().map( |v| {
                let mut i = 0;
                v.fields.iter().filter( |f| !is_skipped( &f.attrs )).map( move |f| {
                    match serde_rename(f) {
                        Some( name ) => name,
                        None => {
                            if let Some( ident ) = f.ident {
                                ident.to_string()
                            } else {
                                i += 1;
                                (i-1).to_string()
                            }
                        }
                    }
                })
            });

            let ftypes1 = data.variants.iter().map( |v|
                v.fields.iter().map( |fields| fields.ty.clone() )
            );
            let ftypes2 = data.variants.iter().map( |v|
                v.fields.iter().map( |fields| fields.ty.clone() )
            );
            let ftypes3 = data.variants.iter().map( |v|
                v.fields.iter().map( |fields| fields.ty.clone() )
            );

            quote! {
                #(
                    -( ::reflection::variant( stringify!( #vnames ))
                        /(
                            #(
                                -( ::reflection::field(
                                        #fnames,
                                        <#ftypes1 as ::reflection::Reflection>::ty(),
                                        <#ftypes2 as ::reflection::Reflection>::name(),
                                        Some( <#ftypes3 as ::reflection::Reflection>::members )))
                            )*
                        )
                    )
                )*
            }
        } 
        Data::Union(_) => unimplemented!()
    }
}