Adds example for dev_mode and updates doc (#13944)

* Adds example for dev_mode and updates doc

* Addresses review comments

* Update frame/examples/dev-mode/src/lib.rs

Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>

* Addresses review comment

---------

Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>

substrate/Cargo.lock

@@ -5986,6 +5986,22 @@ dependencies = [
  "sp-std",
 ]
 
+[[package]]
+name = "pallet-dev-mode"
+version = "4.0.0-dev"
+dependencies = [
+ "frame-support",
+ "frame-system",
+ "log",
+ "pallet-balances",
+ "parity-scale-codec",
+ "scale-info",
+ "sp-core",
+ "sp-io",
+ "sp-runtime",
+ "sp-std",
+]
+
 [[package]]
 name = "pallet-election-provider-multi-phase"
 version = "4.0.0-dev"

substrate/Cargo.toml

@@ -106,6 +106,7 @@ members = [
 	"frame/election-provider-support/solution-type/fuzzer",
 	"frame/examples/basic",
 	"frame/examples/offchain-worker",
+	"frame/examples/dev-mode",
 	"frame/executive",
 	"frame/nis",
 	"frame/grandpa",

substrate/frame/examples/dev-mode/Cargo.toml

@@ -0,0 +1,42 @@
+[package]
+name = "pallet-dev-mode"
+version = "4.0.0-dev"
+authors = ["Parity Technologies <admin@parity.io>"]
+edition = "2021"
+license = "MIT-0"
+homepage = "https://substrate.io"
+repository = "https://github.com/paritytech/substrate/"
+description = "FRAME example pallet"
+readme = "README.md"
+
+[package.metadata.docs.rs]
+targets = ["x86_64-unknown-linux-gnu"]
+
+[dependencies]
+codec = { package = "parity-scale-codec", version = "3.2.2", default-features = false }
+log = { version = "0.4.17", default-features = false }
+scale-info = { version = "2.5.0", default-features = false, features = ["derive"] }
+frame-support = { version = "4.0.0-dev", default-features = false, path = "../../support" }
+frame-system = { version = "4.0.0-dev", default-features = false, path = "../../system" }
+pallet-balances = { version = "4.0.0-dev", default-features = false, path = "../../balances" }
+sp-io = { version = "7.0.0", default-features = false, path = "../../../primitives/io" }
+sp-runtime = { version = "7.0.0", default-features = false, path = "../../../primitives/runtime" }
+sp-std = { version = "5.0.0", default-features = false, path = "../../../primitives/std" }
+
+[dev-dependencies]
+sp-core = { version = "7.0.0", default-features = false, path = "../../../primitives/core" }
+
+[features]
+default = ["std"]
+std = [
+	"codec/std",
+	"frame-support/std",
+	"frame-system/std",
+	"log/std",
+	"pallet-balances/std",
+	"scale-info/std",
+	"sp-io/std",
+	"sp-runtime/std",
+	"sp-std/std",
+]
+try-runtime = ["frame-support/try-runtime"]

substrate/frame/examples/dev-mode/README.md

@@ -0,0 +1,11 @@
+<!-- markdown-link-check-disable -->
+# Dev Mode Example Pallet
+
+A simple example of a FRAME pallet demonstrating
+the ease of requirements for a pallet in dev mode.
+
+Run `cargo doc --package pallet-dev-mode --open` to view this pallet's documentation.
+
+**Dev mode is not meant to be used in production.**
+
+License: MIT-0

substrate/frame/examples/dev-mode/src/lib.rs

@@ -0,0 +1,118 @@
+// 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.
+
+//! <!-- markdown-link-check-disable -->
+//! # Dev Mode Example Pallet
+//!
+//! A simple example of a FRAME pallet demonstrating
+//! the ease of requirements for a pallet in dev mode.
+//!
+//! Run `cargo doc --package pallet-dev-mode --open` to view this pallet's documentation.
+//!
+//! **Dev mode is not meant to be used in production.**
+
+// Ensure we're `no_std` when compiling for Wasm.
+#![cfg_attr(not(feature = "std"), no_std)]
+
+use frame_support::dispatch::DispatchResult;
+use frame_system::ensure_signed;
+
+// Re-export pallet items so that they can be accessed from the crate namespace.
+pub use pallet::*;
+
+#[cfg(test)]
+mod tests;
+
+/// A type alias for the balance type from this pallet's point of view.
+type BalanceOf<T> = <T as pallet_balances::Config>::Balance;
+
+/// Enable `dev_mode` for this pallet.
+#[frame_support::pallet(dev_mode)]
+pub mod pallet {
+	use super::*;
+	use frame_support::pallet_prelude::*;
+	use frame_system::pallet_prelude::*;
+
+	#[pallet::config]
+	pub trait Config: pallet_balances::Config + frame_system::Config {
+		/// The overarching event type.
+		type RuntimeEvent: From<Event<Self>> + IsType<<Self as frame_system::Config>::RuntimeEvent>;
+	}
+
+	// Simple declaration of the `Pallet` type. It is placeholder we use to implement traits and
+	// method.
+	#[pallet::pallet]
+	pub struct Pallet<T>(_);
+
+	#[pallet::call]
+	impl<T: Config> Pallet<T> {
+		#[pallet::call_index(0)]
+		/// No need to define a `weight` attribute here because of `dev_mode`.
+		pub fn add_dummy(origin: OriginFor<T>, id: T::AccountId) -> DispatchResult {
+			ensure_root(origin)?;
+
+			if let Some(mut dummies) = Dummy::<T>::get() {
+				dummies.push(id.clone());
+				Dummy::<T>::set(Some(dummies));
+			} else {
+				Dummy::<T>::set(Some(vec![id.clone()]));
+			}
+
+			// Let's deposit an event to let the outside world know this happened.
+			Self::deposit_event(Event::AddDummy { account: id });
+
+			Ok(())
+		}
+
+		#[pallet::call_index(1)]
+		/// No need to define a `weight` attribute here because of `dev_mode`.
+		pub fn set_bar(
+			origin: OriginFor<T>,
+			#[pallet::compact] new_value: T::Balance,
+		) -> DispatchResult {
+			let sender = ensure_signed(origin)?;
+
+			// Put the new value into storage.
+			<Bar<T>>::insert(&sender, new_value);
+
+			Self::deposit_event(Event::SetBar { account: sender, balance: new_value });
+
+			Ok(())
+		}
+	}
+
+	#[pallet::event]
+	#[pallet::generate_deposit(pub(super) fn deposit_event)]
+	pub enum Event<T: Config> {
+		AddDummy { account: T::AccountId },
+		SetBar { account: T::AccountId, balance: BalanceOf<T> },
+	}
+
+	/// The MEL requirement for bounded pallets is skipped by `dev_mode`.
+	/// This means that all storages are marked as unbounded.
+	/// This is equivalent to specifying `#[pallet::unbounded]` on this type definitions.
+	/// When the dev_mode is removed, we would need to implement implement `MaxEncodedLen`.
+	#[pallet::storage]
+	pub type Dummy<T: Config> = StorageValue<_, Vec<T::AccountId>>;
+
+	/// The Hasher requirement is skipped by `dev_mode`. So, second parameter can be `_`
+	/// and `Blake2_128Concat` is used as a default.
+	/// When the dev_mode is removed, we would need to specify the hasher like so:
+	/// `pub type Bar<T: Config> = StorageMap<_, Blake2_128Concat, T::AccountId, T::Balance>;`.
+	#[pallet::storage]
+	pub type Bar<T: Config> = StorageMap<_, _, T::AccountId, T::Balance>;
+}

substrate/frame/examples/dev-mode/src/tests.rs

@@ -0,0 +1,130 @@
+// 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.
+
+//! Tests for pallet-dev-mode.
+
+use crate::*;
+use frame_support::{assert_ok, traits::ConstU64};
+use sp_core::H256;
+use sp_runtime::{
+	testing::Header,
+	traits::{BlakeTwo256, IdentityLookup},
+	BuildStorage,
+};
+// Reexport crate as its pallet name for construct_runtime.
+use crate as pallet_dev_mode;
+
+type UncheckedExtrinsic = frame_system::mocking::MockUncheckedExtrinsic<Test>;
+type Block = frame_system::mocking::MockBlock<Test>;
+
+// For testing the pallet, we construct a mock runtime.
+frame_support::construct_runtime!(
+	pub enum Test where
+		Block = Block,
+		NodeBlock = Block,
+		UncheckedExtrinsic = UncheckedExtrinsic,
+	{
+		System: frame_system::{Pallet, Call, Config, Storage, Event<T>},
+		Balances: pallet_balances::{Pallet, Call, Storage, Config<T>, Event<T>},
+		Example: pallet_dev_mode::{Pallet, Call, Storage, Event<T>},
+	}
+);
+
+impl frame_system::Config for Test {
+	type BaseCallFilter = frame_support::traits::Everything;
+	type BlockWeights = ();
+	type BlockLength = ();
+	type DbWeight = ();
+	type RuntimeOrigin = RuntimeOrigin;
+	type Index = u64;
+	type BlockNumber = u64;
+	type Hash = H256;
+	type RuntimeCall = RuntimeCall;
+	type Hashing = BlakeTwo256;
+	type AccountId = u64;
+	type Lookup = IdentityLookup<Self::AccountId>;
+	type Header = Header;
+	type RuntimeEvent = RuntimeEvent;
+	type BlockHashCount = ConstU64<250>;
+	type Version = ();
+	type PalletInfo = PalletInfo;
+	type AccountData = pallet_balances::AccountData<u64>;
+	type OnNewAccount = ();
+	type OnKilledAccount = ();
+	type SystemWeightInfo = ();
+	type SS58Prefix = ();
+	type OnSetCode = ();
+	type MaxConsumers = frame_support::traits::ConstU32<16>;
+}
+
+impl pallet_balances::Config for Test {
+	type MaxLocks = ();
+	type MaxReserves = ();
+	type ReserveIdentifier = [u8; 8];
+	type Balance = u64;
+	type DustRemoval = ();
+	type RuntimeEvent = RuntimeEvent;
+	type ExistentialDeposit = ConstU64<1>;
+	type AccountStore = System;
+	type WeightInfo = ();
+	type FreezeIdentifier = ();
+	type MaxFreezes = ();
+	type HoldIdentifier = ();
+	type MaxHolds = ();
+}
+
+impl Config for Test {
+	type RuntimeEvent = RuntimeEvent;
+}
+
+// This function basically just builds a genesis storage key/value store according to
+// our desired mockup.
+pub fn new_test_ext() -> sp_io::TestExternalities {
+	let t = GenesisConfig {
+		// We use default for brevity, but you can configure as desired if needed.
+		system: Default::default(),
+		balances: Default::default(),
+	}
+	.build_storage()
+	.unwrap();
+	t.into()
+}
+
+#[test]
+fn it_works_for_optional_value() {
+	new_test_ext().execute_with(|| {
+		assert_eq!(Dummy::<Test>::get(), None);
+
+		let val1 = 42;
+		assert_ok!(Example::add_dummy(RuntimeOrigin::root(), val1));
+		assert_eq!(Dummy::<Test>::get(), Some(vec![val1]));
+
+		// Check that accumulate works when we have Some value in Dummy already.
+		let val2 = 27;
+		assert_ok!(Example::add_dummy(RuntimeOrigin::root(), val2));
+		assert_eq!(Dummy::<Test>::get(), Some(vec![val1, val2]));
+	});
+}
+
+#[test]
+fn set_dummy_works() {
+	new_test_ext().execute_with(|| {
+		let test_val = 133;
+		assert_ok!(Example::set_bar(RuntimeOrigin::signed(1), test_val.into()));
+		assert_eq!(Bar::<Test>::get(1), Some(test_val));
+	});
+}

substrate/frame/support/procedural/src/lib.rs

@@ -465,6 +465,8 @@ pub fn construct_runtime(input: TokenStream) -> TokenStream {
 /// * All storages are marked as unbounded, meaning you do not need to implement `MaxEncodedLen` on
 ///   storage types. This is equivalent to specifying `#[pallet::unbounded]` on all storage type
 ///   definitions.
+/// * Storage hashers no longer need to be specified and can be replaced by `_`. In dev mode, these
+///   will be replaced by `Blake2_128Concat`.
 ///
 /// Note that the `dev_mode` argument can only be supplied to the `#[pallet]` or
 /// `#[frame_support::pallet]` attribute macro that encloses your pallet module. This argument