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feat(extension): proc macro impl for Extension Trait (#32)
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,16 @@ | ||
| [package] | ||
| name = "xcq-extension-procedural" | ||
| authors.workspace = true | ||
| edition.workspace = true | ||
| repository.workspace = true | ||
| license.workspace = true | ||
| version.workspace = true | ||
|
|
||
| [lib] | ||
| proc-macro = true | ||
|
|
||
| [dependencies] | ||
| syn = { version = "2", features = ["full", "extra-traits"] } | ||
| quote = "1" | ||
| proc-macro2 = "1" | ||
| twox-hash = "1.6.3" |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,182 @@ | ||
| use proc_macro2::TokenStream; | ||
| use quote::quote; | ||
| use std::hash::{Hash, Hasher}; | ||
| use syn::token::Comma; | ||
| use syn::{parse_macro_input, parse_quote, parse_str, spanned::Spanned}; | ||
| use syn::{punctuated::Punctuated, ExprCall, Field, Ident, ItemImpl, Pat, TraitItem, Variant}; | ||
|
|
||
| #[derive(Clone)] | ||
| struct Method { | ||
| /// Function name | ||
| pub name: Ident, | ||
| /// Information on args: `(name, type)` | ||
| pub args: Vec<(Ident, Box<syn::Type>)>, | ||
| } | ||
|
|
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| #[proc_macro_attribute] | ||
| pub fn extension(_args: proc_macro::TokenStream, input: proc_macro::TokenStream) -> proc_macro::TokenStream { | ||
| let input = parse_macro_input!(input as syn::ItemTrait); | ||
|
|
||
| let methods = match methods(&input.items) { | ||
| Ok(method) => method, | ||
| Err(e) => return e.to_compile_error().into(), | ||
| }; | ||
|
|
||
| let call_enum_def = match call_enum_def(&input.ident, &methods) { | ||
| Ok(call_enum_def) => call_enum_def, | ||
| Err(e) => return e.to_compile_error().into(), | ||
| }; | ||
|
|
||
| let dispatchable_impl = dispatchable_impl(&input.ident, &methods); | ||
| let extension_id_impl = extension_id_impl(&input.ident, &input.items); | ||
|
|
||
| let expanded = quote! { | ||
| #input | ||
| #call_enum_def | ||
| #dispatchable_impl | ||
| #extension_id_impl | ||
| }; | ||
| expanded.into() | ||
| } | ||
|
|
||
| fn call_enum_def(trait_ident: &Ident, methods: &[Method]) -> syn::Result<syn::ItemEnum> { | ||
| let mut variants = Punctuated::<Variant, Comma>::new(); | ||
| for method in methods { | ||
| let name = &method.name; | ||
| let mut args = Punctuated::<Field, Comma>::new(); | ||
| for (name, ty) in &method.args { | ||
| let ty = replace_self_to_impl(ty)?; | ||
| args.push(parse_quote! { | ||
| #name: #ty | ||
| }); | ||
| } | ||
| variants.push(parse_quote! { | ||
| #[allow(non_camel_case_types)] | ||
| #name { | ||
| #args | ||
| } | ||
| }); | ||
| } | ||
| // Add phantom data | ||
| variants.push(parse_quote!( | ||
| #[doc(hidden)] | ||
| __Phantom(std::marker::PhantomData<Impl>) | ||
| )); | ||
| Ok(parse_quote!( | ||
| #[derive(Decode)] | ||
| pub enum Call<Impl: #trait_ident> { | ||
| #variants | ||
| } | ||
| )) | ||
| } | ||
|
|
||
| fn dispatchable_impl(trait_ident: &Ident, methods: &[Method]) -> TokenStream { | ||
| let mut pats = Vec::<Pat>::new(); | ||
| for method in methods { | ||
| let name = &method.name; | ||
| let mut args = Punctuated::<Ident, Comma>::new(); | ||
| for (ident, _ty) in &method.args { | ||
| args.push(parse_quote! { | ||
| #ident | ||
| }); | ||
| } | ||
| pats.push(parse_quote! { | ||
| Self::#name { | ||
| #args | ||
| } | ||
| }); | ||
| } | ||
|
|
||
| let mut method_calls = Vec::<ExprCall>::new(); | ||
| for method in methods { | ||
| let name = &method.name; | ||
| let mut args = Punctuated::<Ident, Comma>::new(); | ||
| for (ident, _ty) in &method.args { | ||
| args.push(parse_quote! { | ||
| #ident | ||
| }); | ||
| } | ||
| method_calls.push({ | ||
| parse_quote! { | ||
| Impl::#name(#args) | ||
| } | ||
| }); | ||
| } | ||
|
|
||
| parse_quote! { | ||
| impl<Impl: #trait_ident> xcq_extension::Dispatchable for Call<Impl> { | ||
| fn dispatch(self) -> Result<Vec<u8>, xcq_extension::DispatchError> { | ||
| match self { | ||
| #( #pats => Ok(#method_calls.encode()),)* | ||
| Self::__Phantom(_) => unreachable!(), | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } | ||
|
|
||
| fn extension_id_impl(trait_ident: &Ident, trait_items: &[TraitItem]) -> ItemImpl { | ||
| let extension_id = calculate_hash(trait_ident, trait_items); | ||
| parse_quote! { | ||
| impl<Impl: #trait_ident> xcq_extension::ExtensionId for Call<Impl> { | ||
| const EXTENSION_ID: xcq_extension::ExtensionIdTy = #extension_id; | ||
| } | ||
| } | ||
| } | ||
|
|
||
| // helper functions | ||
| fn methods(trait_items: &[TraitItem]) -> syn::Result<Vec<Method>> { | ||
| let mut methods = vec![]; | ||
| for item in trait_items { | ||
| if let TraitItem::Fn(method) = item { | ||
| let method_name = &method.sig.ident; | ||
| let mut method_args = vec![]; | ||
| for arg in method.sig.inputs.iter() { | ||
| let arg = if let syn::FnArg::Typed(arg) = arg { | ||
| arg | ||
| } else { | ||
| unreachable!("every argument should be typed instead of receiver(self)") | ||
| }; | ||
| let arg_ident = if let syn::Pat::Ident(pat) = &*arg.pat { | ||
| pat.ident.clone() | ||
| } else { | ||
| let msg = "Invalid call, argument must be ident"; | ||
| return Err(syn::Error::new(arg.pat.span(), msg)); | ||
| }; | ||
| method_args.push((arg_ident, arg.ty.clone())) | ||
| } | ||
| methods.push(Method { | ||
| name: method_name.clone(), | ||
| args: method_args, | ||
| }); | ||
| } | ||
| } | ||
| Ok(methods) | ||
| } | ||
|
|
||
| // TODO: refine this to make it more stable | ||
| fn replace_self_to_impl(ty: &syn::Type) -> syn::Result<Box<syn::Type>> { | ||
| let ty_str = quote!(#ty).to_string(); | ||
|
|
||
| let modified_ty_str = ty_str.replace("Self", "Impl"); | ||
|
|
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| let modified_ty = parse_str(&modified_ty_str)?; | ||
|
|
||
| Ok(Box::new(modified_ty)) | ||
| } | ||
|
|
||
| // TODO: currently we only hash on trait ident and function names, | ||
| fn calculate_hash(trait_ident: &Ident, trait_items: &[TraitItem]) -> u64 { | ||
| let mut hasher = twox_hash::XxHash64::default(); | ||
| // reduce the chance of hash collision | ||
| "xcq-ext$".hash(&mut hasher); | ||
| trait_ident.hash(&mut hasher); | ||
| for trait_item in trait_items { | ||
| if let TraitItem::Fn(method) = trait_item { | ||
| // reduce the chance of hash collision | ||
| "@".hash(&mut hasher); | ||
| method.sig.ident.hash(&mut hasher); | ||
| } | ||
| } | ||
| hasher.finish() | ||
| } |
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