pallet_authorship/
lib.rs

1// This file is part of Substrate.
2
3// Copyright (C) Parity Technologies (UK) Ltd.
4// SPDX-License-Identifier: Apache-2.0
5
6// Licensed under the Apache License, Version 2.0 (the "License");
7// you may not use this file except in compliance with the License.
8// You may obtain a copy of the License at
9//
10// 	http://www.apache.org/licenses/LICENSE-2.0
11//
12// Unless required by applicable law or agreed to in writing, software
13// distributed under the License is distributed on an "AS IS" BASIS,
14// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15// See the License for the specific language governing permissions and
16// limitations under the License.
17
18//! Authorship tracking for FRAME runtimes.
19//!
20//! This tracks the current author of the block.
21
22#![cfg_attr(not(feature = "std"), no_std)]
23
24use frame_support::traits::FindAuthor;
25
26pub use pallet::*;
27
28/// An event handler for the authorship pallet. There is a dummy implementation
29/// for `()`, which does nothing.
30#[impl_trait_for_tuples::impl_for_tuples(30)]
31pub trait EventHandler<Author, BlockNumber> {
32	/// Note that the given account ID is the author of the current block.
33	fn note_author(author: Author);
34}
35
36#[frame_support::pallet]
37pub mod pallet {
38	use super::*;
39	use frame_support::pallet_prelude::*;
40	use frame_system::pallet_prelude::*;
41
42	#[pallet::config]
43	pub trait Config: frame_system::Config {
44		/// Find the author of a block.
45		type FindAuthor: FindAuthor<Self::AccountId>;
46		/// An event handler for authored blocks.
47		type EventHandler: EventHandler<Self::AccountId, BlockNumberFor<Self>>;
48	}
49
50	#[pallet::pallet]
51	pub struct Pallet<T>(_);
52
53	#[pallet::hooks]
54	impl<T: Config> Hooks<BlockNumberFor<T>> for Pallet<T> {
55		fn on_initialize(_: BlockNumberFor<T>) -> Weight {
56			if let Some(author) = Self::author() {
57				T::EventHandler::note_author(author);
58			}
59
60			Weight::zero()
61		}
62
63		fn on_finalize(_: BlockNumberFor<T>) {
64			// ensure we never go to trie with these values.
65			<Author<T>>::kill();
66		}
67	}
68
69	#[pallet::storage]
70	#[pallet::whitelist_storage]
71	/// Author of current block.
72	pub(super) type Author<T: Config> = StorageValue<_, T::AccountId, OptionQuery>;
73}
74
75impl<T: Config> Pallet<T> {
76	/// Fetch the author of the block.
77	///
78	/// This is safe to invoke in `on_initialize` implementations, as well
79	/// as afterwards.
80	pub fn author() -> Option<T::AccountId> {
81		// Check the memorized storage value.
82		if let Some(author) = <Author<T>>::get() {
83			return Some(author)
84		}
85
86		let digest = <frame_system::Pallet<T>>::digest();
87		let pre_runtime_digests = digest.logs.iter().filter_map(|d| d.as_pre_runtime());
88		T::FindAuthor::find_author(pre_runtime_digests).inspect(|a| {
89			<Author<T>>::put(&a);
90		})
91	}
92}
93
94#[cfg(test)]
95mod tests {
96	use super::*;
97	use crate as pallet_authorship;
98	use codec::{Decode, Encode};
99	use frame_support::{derive_impl, ConsensusEngineId};
100	use sp_core::H256;
101	use sp_runtime::{
102		generic::DigestItem, testing::Header, traits::Header as HeaderT, BuildStorage,
103	};
104
105	type Block = frame_system::mocking::MockBlock<Test>;
106
107	frame_support::construct_runtime!(
108		pub enum Test
109		{
110			System: frame_system,
111			Authorship: pallet_authorship,
112		}
113	);
114
115	#[derive_impl(frame_system::config_preludes::TestDefaultConfig)]
116	impl frame_system::Config for Test {
117		type Block = Block;
118	}
119
120	impl pallet::Config for Test {
121		type FindAuthor = AuthorGiven;
122		type EventHandler = ();
123	}
124
125	const TEST_ID: ConsensusEngineId = [1, 2, 3, 4];
126
127	pub struct AuthorGiven;
128
129	impl FindAuthor<u64> for AuthorGiven {
130		fn find_author<'a, I>(digests: I) -> Option<u64>
131		where
132			I: 'a + IntoIterator<Item = (ConsensusEngineId, &'a [u8])>,
133		{
134			for (id, mut data) in digests {
135				if id == TEST_ID {
136					return u64::decode(&mut data).ok()
137				}
138			}
139
140			None
141		}
142	}
143
144	fn seal_header(mut header: Header, author: u64) -> Header {
145		{
146			let digest = header.digest_mut();
147			digest.logs.push(DigestItem::PreRuntime(TEST_ID, author.encode()));
148			digest.logs.push(DigestItem::Seal(TEST_ID, author.encode()));
149		}
150
151		header
152	}
153
154	fn create_header(number: u64, parent_hash: H256, state_root: H256) -> Header {
155		Header::new(number, Default::default(), state_root, parent_hash, Default::default())
156	}
157
158	fn new_test_ext() -> sp_io::TestExternalities {
159		let t = frame_system::GenesisConfig::<Test>::default().build_storage().unwrap();
160		t.into()
161	}
162
163	#[test]
164	fn sets_author_lazily() {
165		new_test_ext().execute_with(|| {
166			let author = 42;
167			let mut header =
168				seal_header(create_header(1, Default::default(), [1; 32].into()), author);
169
170			header.digest_mut().pop(); // pop the seal off.
171			System::reset_events();
172			System::initialize(&1, &Default::default(), header.digest());
173
174			assert_eq!(Authorship::author(), Some(author));
175		});
176	}
177}
pallet_authorship/lib.rs

pallet_authorship/
lib.rs
