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// This file is part of Substrate.
// Copyright (C) Parity Technologies (UK) Ltd.
// SPDX-License-Identifier: Apache-2.0
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
use proc_macro2::TokenStream as TokenStream2;
use quote::quote;
use syn::{parse_quote, ItemImpl, ItemTrait, Result};
use crate::{
common::CHANGED_IN_ATTRIBUTE,
utils::{
extract_impl_trait, filter_cfg_attributes, generate_crate_access,
generate_runtime_mod_name_for_trait, get_doc_literals, RequireQualifiedTraitPath,
},
};
/// Get the type parameter argument without lifetime or mutability
/// of a runtime metadata function.
///
/// In the following example, both the `AccountId` and `Nonce` generic
/// type parameters must implement `scale_info::TypeInfo` because they
/// are added into the metadata using `scale_info::meta_type`.
///
/// ```ignore
/// trait ExampleAccountNonceApi<AccountId, Nonce> {
/// fn account_nonce<'a>(account: &'a AccountId) -> Nonce;
/// }
/// ```
///
/// Instead of returning `&'a AccountId` for the first parameter, this function
/// returns `AccountId` to place bounds around it.
fn get_type_param(ty: &syn::Type) -> syn::Type {
// Remove the lifetime and mutability of the type T to
// place bounds around it.
let ty_elem = match &ty {
syn::Type::Reference(reference) => &reference.elem,
syn::Type::Ptr(ptr) => &ptr.elem,
syn::Type::Slice(slice) => &slice.elem,
syn::Type::Array(arr) => &arr.elem,
_ => ty,
};
ty_elem.clone()
}
/// Extract the documentation from the provided attributes.
///
/// It takes into account the `no-metadata-docs` feature.
fn collect_docs(attrs: &[syn::Attribute], crate_: &TokenStream2) -> TokenStream2 {
if cfg!(feature = "no-metadata-docs") {
quote!(#crate_::vec![])
} else {
let docs = get_doc_literals(&attrs);
quote!(#crate_::vec![ #( #docs, )* ])
}
}
/// Generate the runtime metadata of the provided trait.
///
/// The metadata is exposed as a generic function on the hidden module
/// of the trait generated by the `decl_runtime_apis`.
pub fn generate_decl_runtime_metadata(decl: &ItemTrait) -> TokenStream2 {
let crate_ = generate_crate_access();
let mut methods = Vec::new();
// Ensure that any function parameter that relies on the `BlockT` bounds
// also has `TypeInfo + 'static` bounds (required by `scale_info::meta_type`).
//
// For example, if a runtime API defines a method that has an input:
// `fn func(input: <Block as BlockT>::Header)`
// then the runtime metadata will imply `<Block as BlockT>::Header: TypeInfo + 'static`.
//
// This restricts the bounds at the metadata level, without needing to modify the `BlockT`
// itself, since the concrete implementations are already satisfying `TypeInfo`.
let mut where_clause = Vec::new();
for item in &decl.items {
// Collect metadata for methods only.
let syn::TraitItem::Fn(method) = item else { continue };
// Collect metadata only for the latest methods.
let is_changed_in =
method.attrs.iter().any(|attr| attr.path().is_ident(CHANGED_IN_ATTRIBUTE));
if is_changed_in {
continue;
}
let mut inputs = Vec::new();
let signature = &method.sig;
for input in &signature.inputs {
// Exclude `self` from metadata collection.
let syn::FnArg::Typed(typed) = input else { continue };
let pat = &typed.pat;
let name = quote!(#pat).to_string();
let ty = &typed.ty;
where_clause.push(get_type_param(ty));
inputs.push(quote!(
#crate_::metadata_ir::RuntimeApiMethodParamMetadataIR {
name: #name,
ty: #crate_::scale_info::meta_type::<#ty>(),
}
));
}
let output = match &signature.output {
syn::ReturnType::Default => quote!(#crate_::scale_info::meta_type::<()>()),
syn::ReturnType::Type(_, ty) => {
where_clause.push(get_type_param(ty));
quote!(#crate_::scale_info::meta_type::<#ty>())
},
};
// String method name including quotes for constructing `v15::RuntimeApiMethodMetadata`.
let method_name = signature.ident.to_string();
let docs = collect_docs(&method.attrs, &crate_);
// Include the method metadata only if its `cfg` features are enabled.
let attrs = filter_cfg_attributes(&method.attrs);
let deprecation = match crate::utils::get_deprecation(&crate_, &method.attrs) {
Ok(deprecation) => deprecation,
Err(e) => return e.into_compile_error(),
};
methods.push(quote!(
#( #attrs )*
#crate_::metadata_ir::RuntimeApiMethodMetadataIR {
name: #method_name,
inputs: #crate_::vec![ #( #inputs, )* ],
output: #output,
docs: #docs,
deprecation_info: #deprecation,
}
));
}
let trait_name_ident = &decl.ident;
let trait_name = trait_name_ident.to_string();
let docs = collect_docs(&decl.attrs, &crate_);
let deprecation = match crate::utils::get_deprecation(&crate_, &decl.attrs) {
Ok(deprecation) => deprecation,
Err(e) => return e.into_compile_error(),
};
let attrs = filter_cfg_attributes(&decl.attrs);
// The trait generics where already extended with `Block: BlockT`.
let mut generics = decl.generics.clone();
for generic_param in generics.params.iter_mut() {
let syn::GenericParam::Type(ty) = generic_param else { continue };
// Default type parameters are not allowed in functions.
ty.eq_token = None;
ty.default = None;
}
where_clause
.into_iter()
.map(|ty| parse_quote!(#ty: #crate_::scale_info::TypeInfo + 'static))
.for_each(|w| generics.make_where_clause().predicates.push(w));
let (impl_generics, _, where_clause) = generics.split_for_impl();
quote!(
#crate_::frame_metadata_enabled! {
#( #attrs )*
#[inline(always)]
pub fn runtime_metadata #impl_generics () -> #crate_::metadata_ir::RuntimeApiMetadataIR
#where_clause
{
#crate_::metadata_ir::RuntimeApiMetadataIR {
name: #trait_name,
methods: #crate_::vec![ #( #methods, )* ],
docs: #docs,
deprecation_info: #deprecation,
}
}
}
)
}
/// Implement the `runtime_metadata` function on the runtime that
/// generates the metadata for the given traits.
///
/// The metadata of each trait is extracted from the generic function
/// exposed by `generate_decl_runtime_metadata`.
pub fn generate_impl_runtime_metadata(impls: &[ItemImpl]) -> Result<TokenStream2> {
if impls.is_empty() {
return Ok(quote!());
}
let crate_ = generate_crate_access();
// Get the name of the runtime for which the traits are implemented.
let runtime_name = &impls
.get(0)
.expect("Traits should contain at least one implementation; qed")
.self_ty;
let mut metadata = Vec::new();
for impl_ in impls {
let mut trait_ = extract_impl_trait(&impl_, RequireQualifiedTraitPath::Yes)?.clone();
// Implementation traits are always references with a path `impl client::Core<generics> ...`
// The trait name is the last segment of this path.
let trait_name_ident = &trait_
.segments
.last()
.as_ref()
.expect("Trait path should always contain at least one item; qed")
.ident;
// Extract the generics from the trait to pass to the `runtime_metadata`
// function on the hidden module.
let generics = trait_
.segments
.iter()
.find_map(|segment| {
if let syn::PathArguments::AngleBracketed(generics) = &segment.arguments {
Some(generics.clone())
} else {
None
}
})
.expect("Trait path should always contain at least one generic parameter; qed");
let mod_name = generate_runtime_mod_name_for_trait(&trait_name_ident);
// Get absolute path to the `runtime_decl_for_` module by replacing the last segment.
if let Some(segment) = trait_.segments.last_mut() {
*segment = parse_quote!(#mod_name);
}
let attrs = filter_cfg_attributes(&impl_.attrs);
metadata.push(quote!(
#( #attrs )*
#trait_::runtime_metadata::#generics()
));
}
// Each runtime must expose the `runtime_metadata()` to fetch the runtime API metadata.
// The function is implemented by calling `impl_runtime_apis!`.
//
// However, the `construct_runtime!` may be called without calling `impl_runtime_apis!`.
// Rely on the `Deref` trait to differentiate between a runtime that implements
// APIs (by macro impl_runtime_apis!) and a runtime that is simply created (by macro
// construct_runtime!).
//
// Both `InternalConstructRuntime` and `InternalImplRuntimeApis` expose a `runtime_metadata()`
// function. `InternalConstructRuntime` is implemented by the `construct_runtime!` for Runtime
// references (`& Runtime`), while `InternalImplRuntimeApis` is implemented by the
// `impl_runtime_apis!` for Runtime (`Runtime`).
//
// Therefore, the `Deref` trait will resolve the `runtime_metadata` from `impl_runtime_apis!`
// when both macros are called; and will resolve an empty `runtime_metadata` when only the
// `construct_runtime!` is called.
Ok(quote!(
#crate_::frame_metadata_enabled! {
#[doc(hidden)]
trait InternalImplRuntimeApis {
#[inline(always)]
fn runtime_metadata(&self) -> #crate_::vec::Vec<#crate_::metadata_ir::RuntimeApiMetadataIR> {
#crate_::vec![ #( #metadata, )* ]
}
}
#[doc(hidden)]
impl InternalImplRuntimeApis for #runtime_name {}
}
))
}