Adds default config for assets pallet (#3637)

Step in https://github.com/paritytech/polkadot-sdk/issues/171

substrate/frame/assets/src/lib.rs

@@ -226,10 +226,42 @@ pub mod pallet {
 		}
 	}
 
-	#[pallet::config]
+	/// Default implementations of [`DefaultConfig`], which can be used to implement [`Config`].
+	pub mod config_preludes {
+		use super::*;
+		use frame_support::{derive_impl, traits::ConstU64};
+		pub struct TestDefaultConfig;
+
+		#[derive_impl(frame_system::config_preludes::TestDefaultConfig as frame_system::DefaultConfig, no_aggregated_types)]
+		impl frame_system::DefaultConfig for TestDefaultConfig {}
+
+		#[frame_support::register_default_impl(TestDefaultConfig)]
+		impl DefaultConfig for TestDefaultConfig {
+			#[inject_runtime_type]
+			type RuntimeEvent = ();
+			type Balance = u64;
+			type RemoveItemsLimit = ConstU32<5>;
+			type AssetId = u32;
+			type AssetIdParameter = u32;
+			type AssetDeposit = ConstU64<1>;
+			type AssetAccountDeposit = ConstU64<10>;
+			type MetadataDepositBase = ConstU64<1>;
+			type MetadataDepositPerByte = ConstU64<1>;
+			type ApprovalDeposit = ConstU64<1>;
+			type StringLimit = ConstU32<50>;
+			type Extra = ();
+			type CallbackHandle = ();
+			type WeightInfo = ();
+			#[cfg(feature = "runtime-benchmarks")]
+			type BenchmarkHelper = ();
+		}
+	}
+
+	#[pallet::config(with_default)]
 	/// The module configuration trait.
 	pub trait Config<I: 'static = ()>: frame_system::Config {
 		/// The overarching event type.
+		#[pallet::no_default_bounds]
 		type RuntimeEvent: From<Event<Self, I>>
 			+ IsType<<Self as frame_system::Config>::RuntimeEvent>;
 
@@ -262,10 +294,12 @@ pub mod pallet {
 		type AssetIdParameter: Parameter + From<Self::AssetId> + Into<Self::AssetId> + MaxEncodedLen;
 
 		/// The currency mechanism.
+		#[pallet::no_default]
 		type Currency: ReservableCurrency<Self::AccountId>;
 
 		/// Standard asset class creation is only allowed if the origin attempting it and the
 		/// asset class are in this set.
+		#[pallet::no_default]
 		type CreateOrigin: EnsureOriginWithArg<
 			Self::RuntimeOrigin,
 			Self::AssetId,
@@ -274,28 +308,34 @@ pub mod pallet {
 
 		/// The origin which may forcibly create or destroy an asset or otherwise alter privileged
 		/// attributes.
+		#[pallet::no_default]
 		type ForceOrigin: EnsureOrigin<Self::RuntimeOrigin>;
 
 		/// The basic amount of funds that must be reserved for an asset.
 		#[pallet::constant]
+		#[pallet::no_default_bounds]
 		type AssetDeposit: Get<DepositBalanceOf<Self, I>>;
 
 		/// The amount of funds that must be reserved for a non-provider asset account to be
 		/// maintained.
 		#[pallet::constant]
+		#[pallet::no_default_bounds]
 		type AssetAccountDeposit: Get<DepositBalanceOf<Self, I>>;
 
 		/// The basic amount of funds that must be reserved when adding metadata to your asset.
 		#[pallet::constant]
+		#[pallet::no_default_bounds]
 		type MetadataDepositBase: Get<DepositBalanceOf<Self, I>>;
 
 		/// The additional funds that must be reserved for the number of bytes you store in your
 		/// metadata.
 		#[pallet::constant]
+		#[pallet::no_default_bounds]
 		type MetadataDepositPerByte: Get<DepositBalanceOf<Self, I>>;
 
 		/// The amount of funds that must be reserved when creating a new approval.
 		#[pallet::constant]
+		#[pallet::no_default_bounds]
 		type ApprovalDeposit: Get<DepositBalanceOf<Self, I>>;
 
 		/// The maximum length of a name or symbol stored on-chain.
@@ -304,6 +344,7 @@ pub mod pallet {
 
 		/// A hook to allow a per-asset, per-account minimum balance to be enforced. This must be
 		/// respected in all permissionless operations.
+		#[pallet::no_default]
 		type Freezer: FrozenBalance<Self::AssetId, Self::AccountId, Self::Balance>;
 
 		/// Additional data to be stored with an account's asset balance.

substrate/frame/assets/src/mock.rs

@@ -108,27 +108,13 @@ impl AssetsCallbackHandle {
 	}
 }
 
+#[derive_impl(crate::config_preludes::TestDefaultConfig)]
 impl Config for Test {
-	type RuntimeEvent = RuntimeEvent;
-	type Balance = u64;
-	type AssetId = u32;
-	type AssetIdParameter = u32;
 	type Currency = Balances;
 	type CreateOrigin = AsEnsureOriginWithArg<frame_system::EnsureSigned<u64>>;
 	type ForceOrigin = frame_system::EnsureRoot<u64>;
-	type AssetDeposit = ConstU64<1>;
-	type AssetAccountDeposit = ConstU64<10>;
-	type MetadataDepositBase = ConstU64<1>;
-	type MetadataDepositPerByte = ConstU64<1>;
-	type ApprovalDeposit = ConstU64<1>;
-	type StringLimit = ConstU32<50>;
 	type Freezer = TestFreezer;
-	type WeightInfo = ();
 	type CallbackHandle = AssetsCallbackHandle;
-	type Extra = ();
-	type RemoveItemsLimit = ConstU32<5>;
-	#[cfg(feature = "runtime-benchmarks")]
-	type BenchmarkHelper = ();
 }
 
 use std::collections::HashMap;