yfunc_rust_macro/
lib.rs

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#![allow(non_snake_case)]
#![allow(non_upper_case_globals)]
#![allow(unused)]

extern crate proc_macro;
use proc_macro::TokenStream;
use quote::quote;
use syn::{parse_macro_input, Attribute, Data, DeriveInput, Fields};

#[proc_macro_attribute]
pub fn yfunc(attr: TokenStream, input: TokenStream) -> TokenStream {
    let input = parse_macro_input!(input as DeriveInput);
    let class_name = &input.ident;
    let generics = input.generics.clone();
    let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
    let mut generated_token = quote! {};
    match &input.data {
        Data::Struct(data) => {
            // to json
            let token__to_json = quote! {
                impl #impl_generics #class_name #ty_generics #where_clause {
                    pub fn to_json_str(&self) -> YRes<String> {
                        serde_json::to_string(self).map_err(|e| 
                            err!("failed to serialize {} to json string", stringify!(#class_name)).trace(ctx!(e))
                        )
                    }
                    pub fn to_pretty_json_str(&self) -> YRes<String> {
                        serde_json::to_string_pretty(self).map_err(|e| 
                            err!("failed to serialize {} to pretty json string", stringify!(#class_name)).trace(ctx!(e))
                        )
                    }
                }
            };
            if input.attrs.iter().any(|it| has_derive(it, "Serialize")) {
                generated_token.extend(token__to_json);
            }
            // from json
            let token__from_json = quote! {
                impl #impl_generics #class_name #ty_generics #where_clause {
                    pub fn from_json_str(json_string: &str) -> YRes<Self> {
                        Ok(serde_json::from_str(json_string).map_err(|e|
                            err!("failed to deserialize json string to {}", stringify!(#class_name)).trace(ctx!(e))
                        )?)
                    }
                }
            };
            if input.attrs.iter().any(|it| has_derive(it, "Deserialize")) {
                generated_token.extend(token__from_json);
            }
        },
        Data::Enum(data) => {
            let variants = &data.variants;
            // from name
            let tokens__from_name__match_variant = variants.iter().filter_map(|variant| {
                let variant_name = &variant.ident;
                match &variant.fields {
                    Fields::Unit => Some(quote! { stringify!(#variant_name) => Ok(#class_name::#variant_name), }),
                    _ => None,
                }
            });
            let token__from_name = quote! {
                impl #impl_generics #class_name #ty_generics #where_clause {
                    pub fn from_name(variant_name: &str) -> YRes<Self> {
                        match variant_name {
                            #(#tokens__from_name__match_variant)*
                            _ => Err(err!("enum {} has no variant called {}", stringify!(#class_name), variant_name)),
                        }
                    }
                }
            };
            generated_token.extend(token__from_name);
        },
        Data::Union(data) => {},
    }
    let output = quote! {
        #input
        #generated_token
    };
    TokenStream::from(output)
}

fn has_derive(attr: &Attribute, name: &str) -> bool {
    if !attr.path().is_ident("derive") {
        return false;
    }
    let mut ret = false;
    let _ = attr.parse_nested_meta(|meta| {
        if meta.path.is_ident(name) {
            ret = true;
        }
        Ok(())
    });
    ret
}