Implement transfer_all in Balances Pallet

frame/balances/src/benchmarking.rs

@@ -40,7 +40,7 @@ benchmarks_instance_pallet! {
 		let existential_deposit = T::ExistentialDeposit::get();
 		let caller = whitelisted_caller();
 
-		// Give some multiple of the existential deposit + creation fee + transfer fee
+		// Give some multiple of the existential deposit
 		let balance = existential_deposit.saturating_mul(ED_MULTIPLIER.into());
 		let _ = <Balances<T, I> as Currency<_>>::make_free_balance_be(&caller, balance);
 
@@ -130,7 +130,7 @@ benchmarks_instance_pallet! {
 		let source: T::AccountId = account("source", 0, SEED);
 		let source_lookup: <T::Lookup as StaticLookup>::Source = T::Lookup::unlookup(source.clone());
 
-		// Give some multiple of the existential deposit + creation fee + transfer fee
+		// Give some multiple of the existential deposit
 		let balance = existential_deposit.saturating_mul(ED_MULTIPLIER.into());
 		let _ = <Balances<T, I> as Currency<_>>::make_free_balance_be(&source, balance);
 
@@ -154,7 +154,7 @@ benchmarks_instance_pallet! {
 		let existential_deposit = T::ExistentialDeposit::get();
 		let caller = whitelisted_caller();
 
-		// Give some multiple of the existential deposit + creation fee + transfer fee
+		// Give some multiple of the existential deposit
 		let balance = existential_deposit.saturating_mul(ED_MULTIPLIER.into());
 		let _ = <Balances<T, I> as Currency<_>>::make_free_balance_be(&caller, balance);
 
@@ -185,12 +185,14 @@ benchmarks_instance_pallet! {
 		let recipient: T::AccountId = account("recipient", 0, SEED);
 		let recipient_lookup: <T::Lookup as StaticLookup>::Source = T::Lookup::unlookup(recipient.clone());
 
-		// Give the sender account max funds, thus a transfer will not kill account.
-		let _ = <Balances<T, I> as Currency<_>>::make_free_balance_be(&caller, T::Balance::max_value());
+		// Give some multiple of the existential deposit
+		let existential_deposit = T::ExistentialDeposit::get();
+		let balance = existential_deposit.saturating_mul(ED_MULTIPLIER.into());
+		let _ = <Balances<T, I> as Currency<_>>::make_free_balance_be(&caller, balance);
 	}: _(RawOrigin::Signed(caller.clone()), recipient_lookup, false)
 	verify {
 		assert!(Balances::<T, I>::free_balance(&caller).is_zero());
-		assert_eq!(Balances::<T, I>::free_balance(&recipient), T::Balance::max_value());
+		assert_eq!(Balances::<T, I>::free_balance(&recipient), balance);
 	}
 }
 

frame/balances/src/lib.rs

@@ -372,9 +372,22 @@ pub mod pallet {
 
 		/// Transfer the entire transferable balance from the caller account.
 		///
-		/// # <weight>
+		/// NOTE: This function is only attempt to transfer _transferable_ balances. This means that
+		/// any locked, reserved, or existential deposits (when `keep_alive` is `true`), will not be
+		/// transferred by this function. To ensure that this function results in a killed account,
+		/// you might need to prepare the account by removing any reference counters, storage
+		/// deposits, etc...
+		///
+		/// The dispatch origin of this call must be Signed.
+		///
+		/// - `dest`: The recipient of the transfer.
+		/// - `keep_alive`: A boolean to determine if the `transfer_all` operation should send all
+		///   of the funds the account has, causing the sender account to be killed (false), or
+		///   transfer everything except at least the existential deposit, which will guarantee to
+		///   keep the sender account alive (true).
+		///   # <weight>
 		/// - O(1). Just like transfer, but reading the user's transferable balance first.
-		/// #</weight>
+		///   #</weight>
 		#[pallet::weight(T::WeightInfo::transfer_all())]
 		pub fn transfer_all(
 			origin: OriginFor<T>,
@@ -1716,7 +1729,7 @@ impl<T: Config<I>, I: 'static> NamedReservableCurrency<T::AccountId> for Pallet<
 	/// Is a no-op if value to be reserved is zero.
 	fn reserve_named(id: &Self::ReserveIdentifier, who: &T::AccountId, value: Self::Balance) -> DispatchResult {
 		if value.is_zero() { return Ok(()) }
-		
+
 		Reserves::<T, I>::try_mutate(who, |reserves| -> DispatchResult {
 			match reserves.binary_search_by_key(id, |data| data.id) {
 				Ok(index) => {