Makes storage hashers optional in dev mode (#13815)

* Initial changes

* Adds UI test for error when _ is used without dev_mode

* Minor

* ".git/.scripts/commands/fmt/fmt.sh"

* Adds test to verify hasher

---------

Co-authored-by: command-bot <>

substrate/frame/support/test/tests/pallet_ui/dev_mode_without_arg_default_hasher.rs

@@ -0,0 +1,33 @@
+#![cfg_attr(not(feature = "std"), no_std)]
+
+pub use pallet::*;
+
+#[frame_support::pallet]
+pub mod pallet {
+	use frame_support::pallet_prelude::*;
+
+	// The struct on which we build all of our Pallet logic.
+	#[pallet::pallet]
+	pub struct Pallet<T>(_);
+
+	// Your Pallet's configuration trait, representing custom external types and interfaces.
+	#[pallet::config]
+	pub trait Config: frame_system::Config {}
+
+	#[pallet::storage]
+	type MyStorage<T: Config> = StorageValue<_, Vec<u8>>;
+
+	#[pallet::storage]
+	type MyStorageMap<T: Config> = StorageMap<_, _, u32, u64>;
+
+	#[pallet::storage]
+	type MyStorageDoubleMap<T: Config> = StorageDoubleMap<_, _, u32, _, u64, u64>;
+
+	#[pallet::storage]
+	type MyCountedStorageMap<T: Config> = CountedStorageMap<_, _, u32, u64>;
+
+	// Your Pallet's internal functions.
+	impl<T: Config> Pallet<T> {}
+}
+
+fn main() {}

substrate/frame/support/test/tests/pallet_ui/dev_mode_without_arg_default_hasher.stderr

@@ -0,0 +1,19 @@
+error[E0121]: the placeholder `_` is not allowed within types on item signatures for type aliases
+  --> tests/pallet_ui/dev_mode_without_arg_default_hasher.rs:21:47
+   |
+21 |     type MyStorageMap<T: Config> = StorageMap<_, _, u32, u64>;
+   |                                                  ^ not allowed in type signatures
+
+error[E0121]: the placeholder `_` is not allowed within types on item signatures for type aliases
+  --> tests/pallet_ui/dev_mode_without_arg_default_hasher.rs:24:59
+   |
+24 |     type MyStorageDoubleMap<T: Config> = StorageDoubleMap<_, _, u32, _, u64, u64>;
+   |                                                              ^       ^ not allowed in type signatures
+   |                                                              |
+   |                                                              not allowed in type signatures
+
+error[E0121]: the placeholder `_` is not allowed within types on item signatures for type aliases
+  --> tests/pallet_ui/dev_mode_without_arg_default_hasher.rs:27:61
+   |
+27 |     type MyCountedStorageMap<T: Config> = CountedStorageMap<_, _, u32, u64>;
+   |                                                                ^ not allowed in type signatures

substrate/frame/support/test/tests/pallet_ui/pass/dev_mode_valid.rs

@@ -1,5 +1,11 @@
 #![cfg_attr(not(feature = "std"), no_std)]
 
+use frame_support::{
+	traits::{
+		ConstU32,
+	},
+};
+
 pub use pallet::*;
 
 #[frame_support::pallet(dev_mode)]
@@ -19,6 +25,16 @@ pub mod pallet {
 	#[pallet::storage]
 	type MyStorage<T: Config> = StorageValue<_, Vec<u8>>;
 
+	// The Hasher requirement skipped by `dev_mode`.
+	#[pallet::storage]
+	pub type MyStorageMap<T: Config> = StorageMap<_, _, u32, u64>;
+
+	#[pallet::storage]
+	type MyStorageDoubleMap<T: Config> = StorageDoubleMap<_, _, u32, _, u64, u64>;
+
+	#[pallet::storage]
+	type MyCountedStorageMap<T: Config> = CountedStorageMap<_, _, u32, u64>;
+
 	// Your Pallet's callable functions.
 	#[pallet::call]
 	impl<T: Config> Pallet<T> {
@@ -32,4 +48,71 @@ pub mod pallet {
 	impl<T: Config> Pallet<T> {}
 }
 
-fn main() {}
+impl frame_system::Config for Runtime {
+	type BaseCallFilter = frame_support::traits::Everything;
+	type RuntimeOrigin = RuntimeOrigin;
+	type Index = u64;
+	type BlockNumber = u32;
+	type RuntimeCall = RuntimeCall;
+	type Hash = sp_runtime::testing::H256;
+	type Hashing = sp_runtime::traits::BlakeTwo256;
+	type AccountId = u64;
+	type Lookup = sp_runtime::traits::IdentityLookup<Self::AccountId>;
+	type Header = Header;
+	type RuntimeEvent = RuntimeEvent;
+	type BlockHashCount = ConstU32<250>;
+	type BlockWeights = ();
+	type BlockLength = ();
+	type DbWeight = ();
+	type Version = ();
+	type PalletInfo = PalletInfo;
+	type AccountData = ();
+	type OnNewAccount = ();
+	type OnKilledAccount = ();
+	type SystemWeightInfo = ();
+	type SS58Prefix = ();
+	type OnSetCode = ();
+	type MaxConsumers = ConstU32<16>;
+}
+
+pub type Header = sp_runtime::generic::Header<u32, sp_runtime::traits::BlakeTwo256>;
+pub type Block = sp_runtime::generic::Block<Header, UncheckedExtrinsic>;
+pub type UncheckedExtrinsic = sp_runtime::generic::UncheckedExtrinsic<u32, RuntimeCall, (), ()>;
+
+frame_support::construct_runtime!(
+	pub struct Runtime where
+		Block = Block,
+		NodeBlock = Block,
+		UncheckedExtrinsic = UncheckedExtrinsic
+	{
+		// Exclude part `Storage` in order not to check its metadata in tests.
+		System: frame_system exclude_parts { Pallet, Storage },
+		Example: pallet,
+	}
+);
+
+impl pallet::Config for Runtime {
+	
+}
+
+fn main() {
+	use frame_support::{pallet_prelude::*};
+	use storage::unhashed;
+	use sp_io::{
+		hashing::{blake2_128, twox_128},
+		TestExternalities,
+	};
+
+	fn blake2_128_concat(d: &[u8]) -> Vec<u8> {
+		let mut v = blake2_128(d).to_vec();
+		v.extend_from_slice(d);
+		v
+	}
+
+	TestExternalities::default().execute_with(|| {
+		pallet::MyStorageMap::<Runtime>::insert(1, 2);
+		let mut k = [twox_128(b"Example"), twox_128(b"MyStorageMap")].concat();
+		k.extend(1u32.using_encoded(blake2_128_concat));
+		assert_eq!(unhashed::get::<u64>(&k), Some(2u64));
+	});
+}