lib.rs

// Copyright 2019 Parity Technologies (UK) Ltd.
//
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//
// The above copyright notice and this permission notice
// shall be included in all copies or substantial portions
// of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
// ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
// TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
// PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
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extern crate proc_macro;

use inflector::Inflector as _;
use proc_macro::TokenStream;
use quote::{quote, quote_spanned};
use std::collections::HashSet;
use syn::spanned::Spanned as _;

mod api_def;

/// Wraps around one or more API definitions and generates an enum.
///
/// The format within this macro must be:
///
/// ```ignore
/// rpc_api!{
///     Foo { ... }
///     pub(crate) Bar { ... }
/// }
/// ```
///
/// The `Foo` and `Bar` are identifiers, optionally prefixed with a visibility modifier
/// (e.g. `pub`).
///
/// The content of the blocks is the same as the content of a trait definition, except that
/// default implementations for methods are forbidden.
///
/// For each identifier (such as `Foo` and `Bar` in the example above), this macro will generate
/// an enum where each variant corresponds to a function of the definition. Function names are
/// turned into PascalCase to conform to the Rust style guide.
///
/// Each generated enum has a `next_request` method whose signature is:
///
/// ```ignore
/// async fn next_request(server: &'a mut jsonrpsee::raw::RawServer<R, I>) -> Result<Foo<'a, R, I>, std::io::Error>;
/// ```
///
/// This method lets you grab the next request incoming from a server, and parse it to match of
/// the function definitions. Invalid requests are automatically handled.
///
/// Additionally, each generated enum has one method per function definition that lets you perform
/// the method has a client.
///
#[proc_macro]
pub fn rpc_api(input_token_stream: TokenStream) -> TokenStream {
	// Start by parsing the input into what we expect.
	let defs: api_def::ApiDefinitions = match syn::parse(input_token_stream) {
		Ok(d) => d,
		Err(err) => return err.to_compile_error().into(),
	};

	let mut out = Vec::with_capacity(defs.apis.len());
	for api in defs.apis {
		match build_api(api) {
			Ok(a) => out.push(a),
			Err(err) => return err.to_compile_error().into(),
		};
	}

	TokenStream::from(quote! {
		#(#out)*
	})
}

/// Generates the macro output token stream corresponding to a single API.
fn build_api(api: api_def::ApiDefinition) -> Result<proc_macro2::TokenStream, syn::Error> {
	let enum_name = &api.name;

	// TODO: make sure there's no conflict here
	let mut tweaked_generics = api.generics.clone();
	tweaked_generics
		.params
		.insert(0, From::from(syn::LifetimeDef::new(syn::parse_str::<syn::Lifetime>("'a").unwrap())));
	tweaked_generics.params.push(From::from(syn::TypeParam::from(syn::parse_str::<syn::Ident>("R").unwrap())));
	tweaked_generics.params.push(From::from(syn::TypeParam::from(syn::parse_str::<syn::Ident>("I").unwrap())));
	let (impl_generics, ty_generics, where_clause) = tweaked_generics.split_for_impl();
	let generics = api
		.generics
		.params
		.iter()
		.filter_map(|gp| if let syn::GenericParam::Type(tp) = gp { Some(tp.ident.clone()) } else { None })
		.collect::<HashSet<_>>();

	let visibility = &api.visibility;

	let mut variants = Vec::new();
	let mut tmp_variants = Vec::new();
	for function in &api.definitions {
		let function_is_notification = function.is_void_ret_type();
		let variant_name = snake_case_to_camel_case(&function.signature.ident);
		let ret = match &function.signature.output {
			syn::ReturnType::Default => quote! {()},
			syn::ReturnType::Type(_, ty) => quote_spanned!(ty.span()=> #ty),
		};

		let mut params_list = Vec::new();
		for input in function.signature.inputs.iter() {
			let (ty, pat_span, param_variant_name) = match input {
				syn::FnArg::Receiver(_) => {
					return Err(syn::Error::new(
						input.span(),
						"Having `self` is not allowed in RPC queries definitions",
					));
				}
				syn::FnArg::Typed(syn::PatType { ty, pat, .. }) => (ty, pat.span(), param_variant_name(&pat)?),
			};

			params_list.push(quote_spanned!(pat_span=> #param_variant_name: #ty));
		}

		if !function_is_notification {
			if params_list.is_empty() {
				tmp_variants.push(quote_spanned!(function.signature.ident.span()=> #variant_name));
			} else {
				tmp_variants.push(quote_spanned!(function.signature.ident.span()=>
					#variant_name {
						#(#params_list,)*
					}
				));
			}
		}

		if function_is_notification {
			variants.push(quote_spanned!(function.signature.ident.span()=>
				#variant_name {
					#(#params_list,)*
				}
			));
		} else {
			variants.push(quote_spanned!(function.signature.ident.span()=>
				#variant_name {
					respond: jsonrpsee::raw::server::TypedResponder<'a, R, I, #ret>,
					#(#params_list,)*
				}
			));
		}
	}

	let next_request = {
		let mut notifications_blocks = Vec::new();
		let mut function_blocks = Vec::new();
		let mut tmp_to_rq = Vec::new();

		struct GenericParams {
			generics: HashSet<syn::Ident>,
			types: HashSet<syn::Ident>,
		}
		impl<'ast> syn::visit::Visit<'ast> for GenericParams {
			fn visit_ident(&mut self, ident: &'ast syn::Ident) {
				if self.generics.contains(ident) {
					self.types.insert(ident.clone());
				}
			}
		}

		let mut generic_params = GenericParams { generics, types: HashSet::new() };

		for function in &api.definitions {
			let function_is_notification = function.is_void_ret_type();
			let variant_name = snake_case_to_camel_case(&function.signature.ident);
			let rpc_method_name =
				function.attributes.method.clone().unwrap_or_else(|| function.signature.ident.to_string());

			let mut params_builders = Vec::new();
			let mut params_names_list = Vec::new();

			for input in function.signature.inputs.iter() {
				let (ty, param_variant_name, rpc_param_name) = match input {
					syn::FnArg::Receiver(_) => {
						return Err(syn::Error::new(
							input.span(),
							"Having `self` is not allowed in RPC queries definitions",
						));
					}
					syn::FnArg::Typed(syn::PatType { ty, pat, attrs, .. }) => {
						(ty, param_variant_name(&pat)?, rpc_param_name(&pat, &attrs)?)
					}
				};

				syn::visit::visit_type(&mut generic_params, &ty);

				params_names_list.push(quote_spanned!(function.signature.span()=> #param_variant_name));
				if !function_is_notification {
					params_builders.push(quote_spanned!(function.signature.span()=>
						let #param_variant_name: #ty = {
							match request.params().get(#rpc_param_name) {
								Ok(v) => v,
								Err(_) => {
									// TODO: message
									request.respond(Err(jsonrpsee::common::Error::invalid_params(#rpc_param_name)));
									continue;
								}
							}
						};
					));
				} else {
					params_builders.push(quote_spanned!(function.signature.span()=>
						let #param_variant_name: #ty = {
							match request.params().get(#rpc_param_name) {
								Ok(v) => v,
								Err(_) => {
									// TODO: log this?
									continue;
								}
							}
						};
					));
				}
			}

			if function_is_notification {
				notifications_blocks.push(quote_spanned!(function.signature.span()=>
					if method == #rpc_method_name {
						let request = n;
						#(#params_builders)*
						return Ok(#enum_name::#variant_name { #(#params_names_list),* });
					}
				));
			} else {
				function_blocks.push(quote_spanned!(function.signature.span()=>
					if request_outcome.is_none() && method == #rpc_method_name {
						let request = server.request_by_id(&request_id).unwrap();
						#(#params_builders)*
						request_outcome = Some(Tmp::#variant_name { #(#params_names_list),* });
					}
				));

				tmp_to_rq.push(quote_spanned!(function.signature.span()=>
					Some(Tmp::#variant_name { #(#params_names_list),* }) => {
						let request = server.request_by_id(&request_id).unwrap();
						let respond = jsonrpsee::raw::server::TypedResponder::from(request);
						return Ok(#enum_name::#variant_name { respond #(, #params_names_list)* });
					},
				));
			}
		}

		let params_tys = generic_params.types.iter();

		let tmp_generics = if generic_params.types.is_empty() {
			quote!()
		} else {
			quote_spanned!(api.name.span()=>
				<#(#params_tys,)*>
			)
		};

		let on_request = quote_spanned!(api.name.span()=> {
			#[allow(unused)]    // The enum might be empty
			enum Tmp #tmp_generics {
				#(#tmp_variants,)*
			}

			let request_id = r.id();
			let method = r.method().to_owned();

			let mut request_outcome: Option<Tmp #tmp_generics> = None;

			#(#function_blocks)*

			match request_outcome {
				#(#tmp_to_rq)*
				None => server.request_by_id(&request_id).unwrap().respond(Err(jsonrpsee::common::Error::method_not_found())),
			}
		});

		let on_notification = quote_spanned!(api.name.span()=> {
			let method = n.method().to_owned();
			#(#notifications_blocks)*
			// TODO: we received an unknown notification; log this?
		});

		let params_tys = generic_params.types.iter();

		quote_spanned!(api.name.span()=>
			#visibility async fn next_request(server: &'a mut jsonrpsee::raw::RawServer<R, I>) -> core::result::Result<#enum_name #ty_generics, std::io::Error>
				where
					R: jsonrpsee::transport::TransportServer<RequestId = I>,
					I: Clone + PartialEq + Eq + std::hash::Hash + Send + Sync
					#(, #params_tys: jsonrpsee::common::DeserializeOwned)*
			{
				loop {
					match server.next_event().await {
						jsonrpsee::raw::RawServerEvent::Notification(n) => #on_notification,
						jsonrpsee::raw::RawServerEvent::SubscriptionsClosed(_) => unimplemented!(),       // TODO:
						jsonrpsee::raw::RawServerEvent::SubscriptionsReady(_) => unimplemented!(),       // TODO:
						jsonrpsee::raw::RawServerEvent::Request(r) => #on_request,
					}
				}
			}
		)
	};

	let client_impl_block = build_client_impl(&api)?;
	let debug_variants = build_debug_variants(&api)?;

	Ok(quote_spanned!(api.name.span()=>
		#visibility enum #enum_name #tweaked_generics {
			#(#variants),*
		}

		impl #impl_generics #enum_name #ty_generics #where_clause {
			#next_request
		}

		#client_impl_block

		impl #impl_generics std::fmt::Debug for #enum_name #ty_generics #where_clause {
			fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
				match self {
					#(#debug_variants,)*
				}
			}
		}
	))
}

/// Builds the impl block that allow performing outbound JSON-RPC queries.
///
/// Generates the `impl <enum> { }` block containing functions that perform RPC client calls.
fn build_client_impl(api: &api_def::ApiDefinition) -> Result<proc_macro2::TokenStream, syn::Error> {
	let enum_name = &api.name;

	let (impl_generics_org, _, where_clause_org) = api.generics.split_for_impl();
	let lifetimes_org = api.generics.lifetimes();
	let type_params_org = api.generics.type_params();
	let const_params_org = api.generics.const_params();

	let client_functions = build_client_functions(&api)?;

	Ok(quote_spanned!(api.name.span()=>
		// TODO: order between type_params and const_params is undecided
		impl #impl_generics_org #enum_name<'static #(, #lifetimes_org)* #(, #type_params_org)* #(, #const_params_org)*, (), ()>
			#where_clause_org
		{
			#(#client_functions)*
		}
	))
}

/// Builds the functions that allow performing outbound JSON-RPC queries.
///
/// Generates a list of functions that perform RPC client calls.
fn build_client_functions(api: &api_def::ApiDefinition) -> Result<Vec<proc_macro2::TokenStream>, syn::Error> {
	let visibility = &api.visibility;

	let mut client_functions = Vec::new();
	for function in &api.definitions {
		let f_name = &function.signature.ident;
		let ret_ty = match function.signature.output {
			syn::ReturnType::Default => quote!(()),
			syn::ReturnType::Type(_, ref ty) => quote_spanned!(ty.span()=> #ty),
		};
		let rpc_method_name =
			function.attributes.method.clone().unwrap_or_else(|| function.signature.ident.to_string());

		let mut params_list = Vec::new();
		let mut params_to_json = Vec::new();
		let mut params_to_array = Vec::new();
		let mut params_tys = Vec::new();

		for (param_index, input) in function.signature.inputs.iter().enumerate() {
			let (ty, pat_span, rpc_param_name) = match input {
				syn::FnArg::Receiver(_) => {
					return Err(syn::Error::new(
						input.span(),
						"Having `self` is not allowed in RPC queries definitions",
					));
				}
				syn::FnArg::Typed(syn::PatType { ty, pat, attrs, .. }) => {
					(ty, pat.span(), rpc_param_name(&pat, &attrs)?)
				}
			};

			let generated_param_name =
				syn::Ident::new(&format!("param{}", param_index), proc_macro2::Span::call_site());

			params_tys.push(ty);
			params_list.push(quote_spanned!(pat_span=> #generated_param_name: impl Into<#ty>));
			params_to_json.push(quote_spanned!(pat_span=>
				map.insert(
					#rpc_param_name.to_string(),
					jsonrpsee::common::to_value(#generated_param_name.into()).unwrap()        // TODO: don't unwrap
				);
			));
			params_to_array.push(quote_spanned!(pat_span=>
				jsonrpsee::common::to_value(#generated_param_name.into()).unwrap()        // TODO: don't unwrap
			));
		}

		let params_building = if params_list.is_empty() {
			quote! {jsonrpsee::common::Params::None}
		} else if function.attributes.positional_params {
			quote_spanned!(function.signature.span()=>
				jsonrpsee::common::Params::Array(vec![
					#(#params_to_array),*
				])
			)
		} else {
			let params_list_len = params_list.len();
			quote_spanned!(function.signature.span()=>
				jsonrpsee::common::Params::Map({
					let mut map = jsonrpsee::common::JsonMap::with_capacity(#params_list_len);
					#(#params_to_json)*
					map
				})
			)
		};

		let is_notification = function.is_void_ret_type();
		let function_body = if is_notification {
			quote_spanned!(function.signature.span()=>
				client.send_notification(#rpc_method_name, #params_building).await
					.map_err(jsonrpsee::raw::client::RawClientError::Inner)?;
				Ok(())
			)
		} else {
			quote_spanned!(function.signature.span()=>
				let rq_id = client.start_request(#rpc_method_name, #params_building).await
					.map_err(jsonrpsee::raw::client::RawClientError::Inner)?;
				let data = client.request_by_id(rq_id).unwrap().await?;     // TODO: don't unwrap?
				Ok(jsonrpsee::common::from_value(data).unwrap())     // TODO: don't unwrap
			)
		};

		client_functions.push(quote_spanned!(function.signature.span()=>
            // TODO: what if there's a conflict between `client` and a param name?
            #visibility async fn #f_name<C: jsonrpsee::transport::TransportClient>(client: &mut jsonrpsee::raw::RawClient<C> #(, #params_list)*)
                -> core::result::Result<#ret_ty, jsonrpsee::raw::client::RawClientError<<C as jsonrpsee::transport::TransportClient>::Error>>
            where
                #ret_ty: jsonrpsee::common::DeserializeOwned
                #(, #params_tys: jsonrpsee::common::Serialize)*
            {
                #function_body
            }
        ));
	}

	Ok(client_functions)
}

// TODO: better docs
fn build_debug_variants(api: &api_def::ApiDefinition) -> Result<Vec<proc_macro2::TokenStream>, syn::Error> {
	let enum_name = &api.name;
	let mut debug_variants = Vec::new();
	for function in &api.definitions {
		let variant_name = snake_case_to_camel_case(&function.signature.ident);
		debug_variants.push(quote_spanned!(function.signature.ident.span()=>
			#enum_name::#variant_name { /* TODO: params */ .. } => {
				f.debug_struct(stringify!(#enum_name))/* TODO: params */.finish()
			}
		));
	}
	Ok(debug_variants)
}

/// Turns a snake case function name into an UpperCamelCase name suitable to be an enum variant.
fn snake_case_to_camel_case(snake_case: &syn::Ident) -> syn::Ident {
	syn::Ident::new(&snake_case.to_string().to_pascal_case(), snake_case.span())
}

/// Determine the name of the variant in the enum based on the pattern of the function parameter.
fn param_variant_name(pat: &syn::Pat) -> syn::parse::Result<&syn::Ident> {
	match pat {
		// TODO: check other fields of the `PatIdent`
		syn::Pat::Ident(ident) => Ok(&ident.ident),
		_ => unimplemented!(),
	}
}

/// Determine the name of the parameter based on the pattern.
fn rpc_param_name(pat: &syn::Pat, _attrs: &[syn::Attribute]) -> syn::parse::Result<String> {
	// TODO: look in attributes if the user specified a param name
	match pat {
		// TODO: check other fields of the `PatIdent`
		syn::Pat::Ident(ident) => Ok(ident.ident.to_string()),
		_ => unimplemented!(),
	}
}