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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.
//! Implementation of `runtime`.
//!
//! `runtime` implementation is recursive and can generate code which will call itself
//! in order to get all the pallet parts for each pallet.
//!
//! Pallets can define their parts:
//! - Implicitly: `pub type System = frame_system;`
//! - Explicitly: `pub type System = frame_system + Pallet + Call;`
//!
//! The `runtime` transitions from the implicit definition to the explicit one.
//! From the explicit state, Substrate expands the pallets with additional information
//! that is to be included in the runtime metadata.
//!
//! Pallets must provide the `tt_default_parts_v2` macro for these transitions.
//! These are automatically implemented by the `#[pallet::pallet]` macro.
//!
//! This macro also generates the following enums for ease of decoding if the respective type
//! is defined inside `#[runtime::derive]`:
//! - `enum RuntimeCall`: This type contains the information needed to decode extrinsics.
//! - `enum RuntimeEvent`: This type contains the information needed to decode events.
//! - `enum RuntimeError`: While this cannot be used directly to decode `sp_runtime::DispatchError`
//! from the chain, it contains the information needed to decode the
//! `sp_runtime::DispatchError::Module`.
//!
//! # State Transitions
//!
//! ```ignore
//! +----------+
//! | Implicit |
//! +----------+
//! |
//! v
//! +----------+
//! | Explicit |
//! +----------+
//! ```
//!
//! The `runtime` macro transforms the implicit declaration of each pallet
//! `System: frame_system` to an explicit one `System: frame_system + Pallet + Call` using the
//! `tt_default_parts_v2` macro.
//!
//! The `tt_default_parts_v2` macro exposes a plus separated list of pallet parts. For example, the
//! `Event` part is exposed only if the pallet implements an event via `#[pallet::event]` macro.
//! The tokens generated by this macro are `+ Pallet + Call` for our example.
//!
//! The `match_and_insert` macro takes in 3 arguments:
//! - target: This is the `TokenStream` that contains the `runtime` macro.
//! - pattern: The pattern to match against in the target stream.
//! - tokens: The tokens to added after the pattern match.
//!
//! The `runtime` macro uses the `tt_call` to get the default pallet parts via
//! the `tt_default_parts_v2` macro defined by each pallet. The pallet parts are then returned as
//! input to the `match_and_replace` macro.
//! The `match_and_replace` then will modify the `runtime` to expand the implicit
//! definition to the explicit one.
//!
//! For example,
//!
//! ```ignore
//! #[frame_support::runtime]
//! mod runtime {
//! //...
//!
//! #[runtime::pallet_index(0)]
//! pub type System = frame_system; // Implicit definition of parts
//!
//! #[runtime::pallet_index(1)]
//! pub type Balances = pallet_balances; // Implicit definition of parts
//! }
//! ```
//! This call has some implicit pallet parts, thus it will expand to:
//! ```ignore
//! frame_support::__private::tt_call! {
//! macro = [{ pallet_balances::tt_default_parts_v2 }]
//! ~~> frame_support::match_and_insert! {
//! target = [{
//! frame_support::__private::tt_call! {
//! macro = [{ frame_system::tt_default_parts_v2 }]
//! ~~> frame_support::match_and_insert! {
//! target = [{
//! #[frame_support::runtime]
//! mod runtime {
//! //...
//!
//! #[runtime::pallet_index(0)]
//! pub type System = frame_system;
//!
//! #[runtime::pallet_index(1)]
//! pub type Balances = pallet_balances;
//! }
//! }]
//! pattern = [{ System = frame_system }]
//! }
//! }
//! }]
//! pattern = [{ Balances = pallet_balances }]
//! }
//! }
//! ```
//! `tt_default_parts_v2` must be defined. It returns the pallet parts inside some tokens, and
//! then `tt_call` will pipe the returned pallet parts into the input of `match_and_insert`.
//! Thus `match_and_insert` will initially receive the following inputs:
//! ```ignore
//! frame_support::match_and_insert! {
//! target = [{
//! frame_support::match_and_insert! {
//! target = [{
//! #[frame_support::runtime]
//! mod runtime {
//! //...
//!
//! #[runtime::pallet_index(0)]
//! pub type System = frame_system;
//!
//! #[runtime::pallet_index(1)]
//! pub type Balances = pallet_balances;
//! }
//! }]
//! pattern = [{ System = frame_system }]
//! tokens = [{ ::{+ Pallet + Call} }]
//! }
//! }]
//! pattern = [{ Balances = pallet_balances }]
//! tokens = [{ ::{+ Pallet + Call} }]
//! }
//! ```
//! After dealing with `pallet_balances`, the inner `match_and_insert` will expand to:
//! ```ignore
//! frame_support::match_and_insert! {
//! target = [{
//! #[frame_support::runtime]
//! mod runtime {
//! //...
//!
//! #[runtime::pallet_index(0)]
//! pub type System = frame_system; // Implicit definition of parts
//!
//! #[runtime::pallet_index(1)]
//! pub type Balances = pallet_balances + Pallet + Call; // Explicit definition of parts
//! }
//! }]
//! pattern = [{ System = frame_system }]
//! tokens = [{ ::{+ Pallet + Call} }]
//! }
//! ```
//!
//! Which will then finally expand to the following:
//! ```ignore
//! #[frame_support::runtime]
//! mod runtime {
//! //...
//!
//! #[runtime::pallet_index(0)]
//! pub type System = frame_system + Pallet + Call;
//!
//! #[runtime::pallet_index(1)]
//! pub type Balances = pallet_balances + Pallet + Call;
//! }
//! ```
//!
//! This call has no implicit pallet parts, thus it will expand to the runtime construction:
//! ```ignore
//! pub struct Runtime { ... }
//! pub struct Call { ... }
//! impl Call ...
//! pub enum Origin { ... }
//! ...
//! ```
//!
//! Visualizing the entire flow of `#[frame_support::runtime]`, it would look like the following:
//!
//! ```ignore
//! +----------------------+ +------------------------+ +-------------------+
//! | | | (defined in pallet) | | |
//! | runtime | --> | tt_default_parts_v2! | --> | match_and_insert! |
//! | w/ no pallet parts | | | | |
//! +----------------------+ +------------------------+ +-------------------+
//!
//! +----------------------+
//! | |
//! --> | runtime |
//! | w/ pallet parts |
//! +----------------------+
//! ```
pub use parse::Def;
use proc_macro::TokenStream;
use syn::spanned::Spanned;
mod expand;
mod parse;
mod keyword {
syn::custom_keyword!(legacy_ordering);
}
pub fn runtime(attr: TokenStream, tokens: TokenStream) -> TokenStream {
let mut legacy_ordering = false;
if !attr.is_empty() {
if let Ok(_) = syn::parse::<keyword::legacy_ordering>(attr.clone()) {
legacy_ordering = true;
} else {
let msg = "Invalid runtime macro call: unexpected attribute. Macro call must be \
bare, such as `#[frame_support::runtime]` or `#[runtime]`, or must specify the \
`legacy_ordering` attribute, such as `#[frame_support::runtime(legacy_ordering)]` or \
#[runtime(legacy_ordering)].";
let span = proc_macro2::TokenStream::from(attr).span();
return syn::Error::new(span, msg).to_compile_error().into()
}
}
let item = syn::parse_macro_input!(tokens as syn::ItemMod);
match parse::Def::try_from(item) {
Ok(def) => expand::expand(def, legacy_ordering).into(),
Err(e) => e.to_compile_error().into(),
}
}