pallet_example_basic/

lib.rs

// This file is part of Substrate.

// Copyright (C) Parity Technologies (UK) Ltd.
// SPDX-License-Identifier: MIT-0

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// this software and associated documentation files (the "Software"), to deal in
// the Software without restriction, including without limitation the rights to
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// so, subject to the following conditions:

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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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//! # Basic Example Pallet
//!
//! A pallet demonstrating concepts, APIs and structures common to most FRAME runtimes.
//!
//! **This pallet serves as an example and is not meant to be used in production.**
//!
//! > Made with *Substrate*, for *Polkadot*.
//!
//! [![github]](https://github.com/paritytech/polkadot-sdk/tree/master/substrate/frame/examples/basic)
//! [![polkadot]](https://polkadot.com)
//!
//! [polkadot]: https://img.shields.io/badge/polkadot-E6007A?style=for-the-badge&logo=polkadot&logoColor=white
//! [github]: https://img.shields.io/badge/github-8da0cb?style=for-the-badge&labelColor=555555&logo=github
//!
//! ## Pallet API
//!
//! See the [`pallet`] module for more information about the interfaces this pallet exposes,
//! including its configuration trait, dispatchables, storage items, events and errors.
//!
//! ## Overview
//!
//! This pallet provides basic examples of using:
//!
//! - A custom weight calculator able to classify a call's dispatch class (see:
//!   [`frame_support::dispatch::DispatchClass`])
//! - Pallet hooks to implement some custom logic that's executed before and after a block is
//!   imported (see: [`frame_support::traits::Hooks`])
//! - Inherited weight annotation for pallet calls, used to create less repetition for calls that
//!   use the [`Config::WeightInfo`] trait to calculate call weights. This can also be overridden,
//!   as demonstrated by [`Call::set_dummy`].
//! - A private function that performs a storage update.
//! - A simple transaction extension implementation (see:
//!   [`sp_runtime::traits::TransactionExtension`]) which increases the priority of the
//!   [`Call::set_dummy`] if it's present and drops any transaction with an encoded length higher
//!   than 200 bytes.

// Ensure we're `no_std` when compiling for Wasm.
#![cfg_attr(not(feature = "std"), no_std)]

extern crate alloc;

use alloc::vec::Vec;
use codec::{Decode, DecodeWithMemTracking, Encode};
use core::marker::PhantomData;
use frame_support::{
	dispatch::{ClassifyDispatch, DispatchClass, DispatchResult, Pays, PaysFee, WeighData},
	pallet_prelude::TransactionSource,
	traits::IsSubType,
	weights::Weight,
};
use frame_system::ensure_signed;
use log::info;
use scale_info::TypeInfo;
use sp_runtime::{
	impl_tx_ext_default,
	traits::{
		Bounded, DispatchInfoOf, DispatchOriginOf, SaturatedConversion, Saturating,
		TransactionExtension, ValidateResult,
	},
	transaction_validity::{InvalidTransaction, ValidTransaction},
};

// Re-export pallet items so that they can be accessed from the crate namespace.
pub use pallet::*;

#[cfg(test)]
mod tests;

mod benchmarking;
pub mod weights;
pub use weights::*;

/// A type alias for the balance type from this pallet's point of view.
type BalanceOf<T> = <T as pallet_balances::Config>::Balance;
const MILLICENTS: u32 = 1_000_000_000;

// A custom weight calculator tailored for the dispatch call `set_dummy()`. This actually examines
// the arguments and makes a decision based upon them.
//
// The `WeightData<T>` trait has access to the arguments of the dispatch that it wants to assign a
// weight to. Nonetheless, the trait itself cannot make any assumptions about what the generic type
// of the arguments (`T`) is. Based on our needs, we could replace `T` with a more concrete type
// while implementing the trait. The `pallet::weight` expects whatever implements `WeighData<T>` to
// replace `T` with a tuple of the dispatch arguments. This is exactly how we will craft the
// implementation below.
//
// The rules of `WeightForSetDummy` are as follows:
// - The final weight of each dispatch is calculated as the argument of the call multiplied by the
//   parameter given to the `WeightForSetDummy`'s constructor.
// - assigns a dispatch class `operational` if the argument of the call is more than 1000.
//
// More information can be read at:
//   - https://docs.substrate.io/main-docs/build/tx-weights-fees/
//
// Manually configuring weight is an advanced operation and what you really need may well be
//   fulfilled by running the benchmarking toolchain. Refer to `benchmarking.rs` file.
struct WeightForSetDummy<T: pallet_balances::Config>(BalanceOf<T>);

impl<T: pallet_balances::Config> WeighData<(&BalanceOf<T>,)> for WeightForSetDummy<T> {
	fn weigh_data(&self, target: (&BalanceOf<T>,)) -> Weight {
		let multiplier = self.0;
		// *target.0 is the amount passed into the extrinsic
		let cents = *target.0 / <BalanceOf<T>>::from(MILLICENTS);
		Weight::from_parts((cents * multiplier).saturated_into::<u64>(), 0)
	}
}

impl<T: pallet_balances::Config> ClassifyDispatch<(&BalanceOf<T>,)> for WeightForSetDummy<T> {
	fn classify_dispatch(&self, target: (&BalanceOf<T>,)) -> DispatchClass {
		if *target.0 > <BalanceOf<T>>::from(1000u32) {
			DispatchClass::Operational
		} else {
			DispatchClass::Normal
		}
	}
}

impl<T: pallet_balances::Config> PaysFee<(&BalanceOf<T>,)> for WeightForSetDummy<T> {
	fn pays_fee(&self, _target: (&BalanceOf<T>,)) -> Pays {
		Pays::Yes
	}
}

// Definition of the pallet logic, to be aggregated at runtime definition through
// `construct_runtime`.
#[frame_support::pallet]
pub mod pallet {
	// Import various types used to declare pallet in scope.
	use super::*;
	use frame_support::pallet_prelude::*;
	use frame_system::pallet_prelude::*;

	/// Our pallet's configuration trait. All our types and constants go in here. If the
	/// pallet is dependent on specific other pallets, then their configuration traits
	/// should be added to our implied traits list.
	///
	/// `frame_system::Config` should always be included.
	#[pallet::config]
	pub trait Config: pallet_balances::Config + frame_system::Config {
		// Setting a constant config parameter from the runtime
		#[pallet::constant]
		type MagicNumber: Get<Self::Balance>;

		/// Type representing the weight of this pallet
		type WeightInfo: WeightInfo;
	}

	// Simple declaration of the `Pallet` type. It is placeholder we use to implement traits and
	// method.
	#[pallet::pallet]
	pub struct Pallet<T>(_);

	// This pallet implements the [`frame_support::traits::Hooks`] trait to define some logic to
	// execute in some context.
	#[pallet::hooks]
	impl<T: Config> Hooks<BlockNumberFor<T>> for Pallet<T> {
		// `on_initialize` is executed at the beginning of the block before any extrinsic are
		// dispatched.
		//
		// This function must return the weight consumed by `on_initialize` and `on_finalize`.
		fn on_initialize(_n: BlockNumberFor<T>) -> Weight {
			// Anything that needs to be done at the start of the block.
			// We don't do anything here.
			Weight::zero()
		}

		// `on_finalize` is executed at the end of block after all extrinsic are dispatched.
		fn on_finalize(_n: BlockNumberFor<T>) {
			// Perform necessary data/state clean up here.
		}

		// A runtime code run after every block and have access to extended set of APIs.
		//
		// For instance you can generate extrinsics for the upcoming produced block.
		fn offchain_worker(_n: BlockNumberFor<T>) {
			// We don't do anything here.
			// but we could dispatch extrinsic (transaction/unsigned/inherent) using
			// sp_io::submit_extrinsic.
			// To see example on offchain worker, please refer to example-offchain-worker pallet
			// accompanied in this repository.
		}
	}

	// The call declaration. This states the entry points that we handle. The
	// macro takes care of the marshalling of arguments and dispatch.
	//
	// Anyone can have these functions execute by signing and submitting
	// an extrinsic. Ensure that calls into each of these execute in a time, memory and
	// using storage space proportional to any costs paid for by the caller or otherwise the
	// difficulty of forcing the call to happen.
	//
	// Generally you'll want to split these into three groups:
	// - Public calls that are signed by an external account.
	// - Root calls that are allowed to be made only by the governance system.
	// - Unsigned calls that can be of two kinds:
	//   * "Inherent extrinsics" that are opinions generally held by the block authors that build
	//     child blocks.
	//   * Unsigned Transactions that are of intrinsic recognizable utility to the network, and are
	//     validated by the runtime.
	//
	// Information about where this dispatch initiated from is provided as the first argument
	// "origin". As such functions must always look like:
	//
	// `fn foo(origin: OriginFor<T>, bar: Bar, baz: Baz) -> DispatchResultWithPostInfo { ... }`
	//
	// The `DispatchResultWithPostInfo` is required as part of the syntax (and can be found at
	// `pallet_prelude::DispatchResultWithPostInfo`).
	//
	// There are three entries in the `frame_system::Origin` enum that correspond
	// to the above bullets: `::Signed(AccountId)`, `::Root` and `::None`. You should always match
	// against them as the first thing you do in your function. There are three convenience calls
	// in system that do the matching for you and return a convenient result: `ensure_signed`,
	// `ensure_root` and `ensure_none`.
	#[pallet::call(weight(<T as Config>::WeightInfo))]
	impl<T: Config> Pallet<T> {
		/// This is your public interface. Be extremely careful.
		/// This is just a simple example of how to interact with the pallet from the external
		/// world.
		// This just increases the value of `Dummy` by `increase_by`.
		//
		// Since this is a dispatched function there are two extremely important things to
		// remember:
		//
		// - MUST NOT PANIC: Under no circumstances (save, perhaps, storage getting into an
		// irreparably damaged state) must this function panic.
		// - NO SIDE-EFFECTS ON ERROR: This function must either complete totally (and return
		// `Ok(())` or it must have no side-effects on storage and return `Err('Some reason')`.
		//
		// The first is relatively easy to audit for - just ensure all panickers are removed from
		// logic that executes in production (which you do anyway, right?!). To ensure the second
		// is followed, you should do all tests for validity at the top of your function. This
		// is stuff like checking the sender (`origin`) or that state is such that the operation
		// makes sense.
		//
		// Once you've determined that it's all good, then enact the operation and change storage.
		// If you can't be certain that the operation will succeed without substantial computation
		// then you have a classic blockchain attack scenario. The normal way of managing this is
		// to attach a bond to the operation. As the first major alteration of storage, reserve
		// some value from the sender's account (`Balances` Pallet has a `reserve` function for
		// exactly this scenario). This amount should be enough to cover any costs of the
		// substantial execution in case it turns out that you can't proceed with the operation.
		//
		// If it eventually transpires that the operation is fine and, therefore, that the
		// expense of the checks should be borne by the network, then you can refund the reserved
		// deposit. If, however, the operation turns out to be invalid and the computation is
		// wasted, then you can burn it or repatriate elsewhere.
		//
		// Security bonds ensure that attackers can't game it by ensuring that anyone interacting
		// with the system either progresses it or pays for the trouble of faffing around with
		// no progress.
		//
		// If you don't respect these rules, it is likely that your chain will be attackable.
		//
		// Each transaction must define a `#[pallet::weight(..)]` attribute to convey a set of
		// static information about its dispatch. FRAME System and FRAME Executive pallet then use
		// this information to properly execute the transaction, whilst keeping the total load of
		// the chain in a moderate rate.
		//
		// The parenthesized value of the `#[pallet::weight(..)]` attribute can be any type that
		// implements a set of traits, namely [`WeighData`], [`ClassifyDispatch`], and
		// [`PaysFee`]. The first conveys the weight (a numeric representation of pure
		// execution time and difficulty) of the transaction and the second demonstrates the
		// [`DispatchClass`] of the call, the third gives whereas extrinsic must pay fees or not.
		// A higher weight means a larger transaction (less of which can be placed in a single
		// block).
		//
		// The weight for this extrinsic we rely on the auto-generated `WeightInfo` from the
		// benchmark toolchain.
		#[pallet::call_index(0)]
		pub fn accumulate_dummy(origin: OriginFor<T>, increase_by: T::Balance) -> DispatchResult {
			// This is a public call, so we ensure that the origin is some signed account.
			let _sender = ensure_signed(origin)?;

			// Read the value of dummy from storage.
			// let dummy = Dummy::<T>::get();

			// Calculate the new value.
			// let new_dummy = dummy.map_or(increase_by, |dummy| dummy + increase_by);

			// Put the new value into storage.
			// <Dummy<T>>::put(new_dummy);
			// Will also work with a reference:
			// <Dummy<T>>::put(&new_dummy);

			// Here's the new one of read and then modify the value.
			<Dummy<T>>::mutate(|dummy| {
				// Using `saturating_add` instead of a regular `+` to avoid overflowing
				let new_dummy = dummy.map_or(increase_by, |d| d.saturating_add(increase_by));
				*dummy = Some(new_dummy);
			});

			// Let's deposit an event to let the outside world know this happened.
			Self::deposit_event(Event::AccumulateDummy { balance: increase_by });

			// All good, no refund.
			Ok(())
		}

		/// A privileged call; in this case it resets our dummy value to something new.
		// Implementation of a privileged call. The `origin` parameter is ROOT because
		// it's not (directly) from an extrinsic, but rather the system as a whole has decided
		// to execute it. Different runtimes have different reasons for allow privileged
		// calls to be executed - we don't need to care why. Because it's privileged, we can
		// assume it's a one-off operation and substantial processing/storage/memory can be used
		// without worrying about gameability or attack scenarios.
		//
		// The weight for this extrinsic we use our own weight object `WeightForSetDummy` to
		// determine its weight
		#[pallet::call_index(1)]
		#[pallet::weight(WeightForSetDummy::<T>(<BalanceOf<T>>::from(100u32)))]
		pub fn set_dummy(
			origin: OriginFor<T>,
			#[pallet::compact] new_value: T::Balance,
		) -> DispatchResult {
			ensure_root(origin)?;

			// Print out log or debug message in the console via log::{error, warn, info, debug,
			// trace}, accepting format strings similar to `println!`.
			// https://paritytech.github.io/substrate/master/sp_io/logging/fn.log.html
			// https://paritytech.github.io/substrate/master/frame_support/constant.LOG_TARGET.html
			info!("New value is now: {:?}", new_value);

			// Put the new value into storage.
			<Dummy<T>>::put(new_value);

			Self::deposit_event(Event::SetDummy { balance: new_value });

			// All good, no refund.
			Ok(())
		}
	}

	/// Events are a simple means of reporting specific conditions and
	/// circumstances that have happened that users, Dapps and/or chain explorers would find
	/// interesting and otherwise difficult to detect.
	#[pallet::event]
	/// This attribute generate the function `deposit_event` to deposit one of this pallet event,
	/// it is optional, it is also possible to provide a custom implementation.
	#[pallet::generate_deposit(pub(super) fn deposit_event)]
	pub enum Event<T: Config> {
		// Just a normal `enum`, here's a dummy event to ensure it compiles.
		/// Dummy event, just here so there's a generic type that's used.
		AccumulateDummy {
			balance: BalanceOf<T>,
		},
		SetDummy {
			balance: BalanceOf<T>,
		},
		SetBar {
			account: T::AccountId,
			balance: BalanceOf<T>,
		},
	}

	// pallet::storage attributes allow for type-safe usage of the Substrate storage database,
	// so you can keep things around between blocks.
	//
	// Any storage must be one of `StorageValue`, `StorageMap` or `StorageDoubleMap`.
	// The first generic holds the prefix to use and is generated by the macro.
	// The query kind is either `OptionQuery` (the default) or `ValueQuery`.
	// - for `type Foo<T> = StorageValue<_, u32, OptionQuery>`:
	//   - `Foo::put(1); Foo::get()` returns `Some(1)`;
	//   - `Foo::kill(); Foo::get()` returns `None`.
	// - for `type Foo<T> = StorageValue<_, u32, ValueQuery>`:
	//   - `Foo::put(1); Foo::get()` returns `1`;
	//   - `Foo::kill(); Foo::get()` returns `0` (u32::default()).
	#[pallet::storage]
	pub(super) type Dummy<T: Config> = StorageValue<_, T::Balance>;

	// A map that has enumerable entries.
	#[pallet::storage]
	pub(super) type Bar<T: Config> = StorageMap<_, Blake2_128Concat, T::AccountId, T::Balance>;

	// this one uses the query kind: `ValueQuery`, we'll demonstrate the usage of 'mutate' API.
	#[pallet::storage]
	pub(super) type Foo<T: Config> = StorageValue<_, T::Balance, ValueQuery>;

	#[pallet::storage]
	pub type CountedMap<T> = CountedStorageMap<_, Blake2_128Concat, u8, u16>;

	// The genesis config type.
	#[pallet::genesis_config]
	#[derive(frame_support::DefaultNoBound)]
	pub struct GenesisConfig<T: Config> {
		pub dummy: T::Balance,
		pub bar: Vec<(T::AccountId, T::Balance)>,
		pub foo: T::Balance,
	}

	// The build of genesis for the pallet.
	#[pallet::genesis_build]
	impl<T: Config> BuildGenesisConfig for GenesisConfig<T> {
		fn build(&self) {
			<Dummy<T>>::put(&self.dummy);
			for (a, b) in &self.bar {
				<Bar<T>>::insert(a, b);
			}
			<Foo<T>>::put(&self.foo);
		}
	}
}

// The main implementation block for the pallet. Functions here fall into three broad
// categories:
// - Public interface. These are functions that are `pub` and generally fall into inspector
// functions that do not write to storage and operation functions that do.
// - Private functions. These are your usual private utilities unavailable to other pallets.
impl<T: Config> Pallet<T> {
	// Add public immutables and private mutables.
	#[allow(dead_code)]
	fn accumulate_foo(origin: T::RuntimeOrigin, increase_by: T::Balance) -> DispatchResult {
		let _sender = ensure_signed(origin)?;

		let prev = Foo::<T>::get();
		// Because Foo has 'default', the type of 'foo' in closure is the raw type instead of an
		// Option<> type.
		let result = Foo::<T>::mutate(|foo| {
			*foo = foo.saturating_add(increase_by);
			*foo
		});
		assert!(prev + increase_by == result);

		Ok(())
	}
}

// Similar to other FRAME pallets, your pallet can also define a transaction extension and perform
// some checks and [pre/post]processing [before/after] the transaction. A transaction extension can
// be any decodable type that implements `TransactionExtension`. See the trait definition for the
// full list of bounds. As a convention, you can follow this approach to create an extension for
// your pallet:
//   - If the extension does not carry any data, then use a tuple struct with just a `marker`
//     (needed for the compiler to accept `T: Config`) will suffice.
//   - Otherwise, create a tuple struct which contains the external data. Of course, for the entire
//     struct to be decodable, each individual item also needs to be decodable.
//
// Note that a transaction extension can also indicate that a particular data must be present in the
// _signing payload_ of a transaction by providing an implementation for the `implicit` method. This
// example will not cover this type of extension. See `CheckSpecVersion` in [FRAME
// System](https://github.com/paritytech/polkadot-sdk/tree/master/substrate/frame/system#signed-extensions)
// for an example.
//
// Using the extension, you can add some hooks to the life cycle of each transaction. Note that by
// default, an extension is applied to all `Call` functions (i.e. all transactions). the `Call` enum
// variant is given to each function of `TransactionExtension`. Hence, you can filter based on
// pallet or a particular call if needed.
//
// Some extra information, such as encoded length, some static dispatch info like weight and the
// sender of the transaction (if signed) are also provided.
//
// The full list of hooks that can be added to a transaction extension can be found in the
// `TransactionExtension` trait definition.
//
// The transaction extensions are aggregated in the runtime file of a substrate chain. All
// extensions should be aggregated in a tuple and passed to the `CheckedExtrinsic` and
// `UncheckedExtrinsic` types defined in the runtime. Lookup `pub type TxExtension = (...)` in
// `node/runtime` and `node-template` for an example of this.

/// A simple transaction extension that checks for the `set_dummy` call. In that case, it increases
/// the priority and prints some log.
///
/// Additionally, it drops any transaction with an encoded length higher than 200 bytes. No
/// particular reason why, just to demonstrate the power of transaction extensions.
#[derive(Encode, Decode, DecodeWithMemTracking, Clone, Eq, PartialEq, TypeInfo)]
#[scale_info(skip_type_params(T))]
pub struct WatchDummy<T: Config + Send + Sync>(PhantomData<T>);

impl<T: Config + Send + Sync> core::fmt::Debug for WatchDummy<T> {
	fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
		write!(f, "WatchDummy")
	}
}

impl<T: Config + Send + Sync> TransactionExtension<<T as frame_system::Config>::RuntimeCall>
	for WatchDummy<T>
where
	<T as frame_system::Config>::RuntimeCall: IsSubType<Call<T>>,
{
	const IDENTIFIER: &'static str = "WatchDummy";
	type Implicit = ();
	type Pre = ();
	type Val = ();

	fn validate(
		&self,
		origin: DispatchOriginOf<<T as frame_system::Config>::RuntimeCall>,
		call: &<T as frame_system::Config>::RuntimeCall,
		_info: &DispatchInfoOf<<T as frame_system::Config>::RuntimeCall>,
		len: usize,
		_self_implicit: Self::Implicit,
		_inherited_implication: &impl Encode,
		_source: TransactionSource,
	) -> ValidateResult<Self::Val, <T as frame_system::Config>::RuntimeCall> {
		// if the transaction is too big, just drop it.
		if len > 200 {
			return Err(InvalidTransaction::ExhaustsResources.into())
		}

		// check for `set_dummy`
		let validity = match call.is_sub_type() {
			Some(Call::set_dummy { .. }) => {
				sp_runtime::print("set_dummy was received.");

				let valid_tx =
					ValidTransaction { priority: Bounded::max_value(), ..Default::default() };
				valid_tx
			},
			_ => Default::default(),
		};
		Ok((validity, (), origin))
	}
	impl_tx_ext_default!(<T as frame_system::Config>::RuntimeCall; weight prepare);
}