Update value adjustment for wasm payable calls.

pallets/xvm/src/lib.rs

@@ -37,10 +37,7 @@
 
 #![cfg_attr(not(feature = "std"), no_std)]
 
-use frame_support::{
-    ensure,
-    traits::{Currency, Get},
-};
+use frame_support::{ensure, traits::Currency};
 use pallet_contracts::{CollectEvents, DebugInfo, Determinism};
 use pallet_evm::GasWeightMapping;
 use parity_scale_codec::Decode;
@@ -87,9 +84,6 @@ pub mod pallet {
         /// `CheckedEthereumTransact` implementation.
         type EthereumTransact: CheckedEthereumTransact;
 
-        /// Existential deposit of currency for payable calls.
-        type ExistentialDeposit: Get<Balance>;
-
         /// Weight information for extrinsics in this pallet.
         type WeightInfo: WeightInfo;
     }
@@ -256,10 +250,21 @@ where
             T::Lookup::lookup(decoded).map_err(|_| error)
         }?;
 
-        // TODO: maybe max(source_balance - existential_deposit, value)? might be overkill
-        // Adjust value to account for existential deposit, as `pallet-contracts`
-        // respects it on transfer.
-        let adjusted_value = value.saturating_sub(T::ExistentialDeposit::get());
+        // Adjust `value` if needed, to make sure `source` balance won't be below ED after calling
+        // a payable contract. This is needed as `pallet-contracts` always respects `source` ED.
+        // Without the adjustment, the first call from any `source` to a payable contract will
+        // always fail.
+        //
+        // Only the first call to a payable contract results less `value` by ED amount, the following
+        // ones will not be affected.
+        let source_balance = T::Currency::free_balance(&source);
+        let existential_deposit = T::Currency::minimum_balance();
+        let killing_source = source_balance.saturating_sub(value) < existential_deposit;
+        let adjusted_value = if killing_source {
+            value.saturating_sub(existential_deposit)
+        } else {
+            value
+        };
 
         // With overheads, less weight is available.
         let weight_limit = context

pallets/xvm/src/mock.rs

@@ -181,7 +181,6 @@ impl pallet_xvm::Config for TestRuntime {
     type GasWeightMapping = MockGasWeightMapping;
     type AccountMapping = HashedAccountMapping;
     type EthereumTransact = MockEthereumTransact;
-    type ExistentialDeposit = ConstU128<2>;
     type WeightInfo = weights::SubstrateWeight<TestRuntime>;
 }
 

runtime/local/src/lib.rs

@@ -475,7 +475,6 @@ impl pallet_xvm::Config for Runtime {
     type GasWeightMapping = pallet_evm::FixedGasWeightMapping<Self>;
     type AccountMapping = HashedAccountMapping;
     type EthereumTransact = EthereumChecked;
-    type ExistentialDeposit = ExistentialDeposit;
     type WeightInfo = pallet_xvm::weights::SubstrateWeight<Runtime>;
 }
 

runtime/shibuya/src/lib.rs

@@ -790,7 +790,6 @@ impl pallet_xvm::Config for Runtime {
     type GasWeightMapping = pallet_evm::FixedGasWeightMapping<Self>;
     type AccountMapping = HashedAccountMapping;
     type EthereumTransact = EthereumChecked;
-    type ExistentialDeposit = ExistentialDeposit;
     type WeightInfo = pallet_xvm::weights::SubstrateWeight<Runtime>;
 }
 

tests/integration/src/xvm.rs

@@ -157,7 +157,7 @@ fn evm_payable_call_via_xvm_works() {
     new_test_ext().execute_with(|| {
         let evm_payable_addr = deploy_evm_contract(EVM_PAYABLE);
 
-        let value = 1_000_000_000;
+        let value = UNIT;
         assert_ok!(Xvm::call(
             Context {
                 source_vm_id: VmId::Wasm,
@@ -199,7 +199,8 @@ fn wasm_payable_call_via_xvm_works() {
     new_test_ext().execute_with(|| {
         let contract_addr = deploy_wasm_contract("payable");
 
-        let value = 1_000_000_000;
+        let prev_balance = Balances::free_balance(&contract_addr);
+        let value = UNIT;
         assert_ok!(Xvm::call(
             Context {
                 source_vm_id: VmId::Evm,
@@ -212,7 +213,10 @@ fn wasm_payable_call_via_xvm_works() {
             hex::decode("0000002a").unwrap(),
             value
         ));
-        assert_eq!(Balances::free_balance(contract_addr.clone()), value,);
+        assert_eq!(
+            Balances::free_balance(contract_addr.clone()),
+            value + prev_balance
+        );
     });
 }
 
@@ -239,7 +243,7 @@ fn calling_wasm_payable_from_evm_works() {
             vec![],
         ));
         // `pallet-contracts` respects the existential deposit of caller. The actual amount
-        // it got is `value - ExistentialDeposit`. Adding to its existing balance and we got `value`.
+        // it got is `value - ExistentialDeposit`. Adding to its existing balance results `value`.
         assert_eq!(
             Balances::free_balance(&wasm_payable_addr),
             value,
@@ -248,6 +252,34 @@ fn calling_wasm_payable_from_evm_works() {
             Balances::free_balance(&account_id_from(call_wasm_payable_addr)),
             ExistentialDeposit::get(),
         );
+
+        let value = 1_000_000_000;
+        assert_ok!(EVM::call(
+            RuntimeOrigin::root(),
+            alith(),
+            call_wasm_payable_addr.clone(),
+            // to: 0x00a8f69d59df362b69a8d4acdb9001eb3e1b8d067b8fdaa70081aed945bde5c48c
+            // input: 0x0000002a (deposit)
+            // value: 1000000000
+            hex::decode("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").unwrap(),
+            U256::from(value),
+            1_000_000,
+            U256::from(DefaultBaseFeePerGas::get()),
+            None,
+            None,
+            vec![],
+        ));
+        // For the second call with the same value, the wasm payable contract will receive
+        // the full amount, as the EVM contract already has enough balance for existential
+        // deposit.
+        assert_eq!(
+            Balances::free_balance(&wasm_payable_addr),
+            2 * value,
+        );
+        assert_eq!(
+            Balances::free_balance(&account_id_from(call_wasm_payable_addr)),
+            ExistentialDeposit::get(),
+        );
     });
 }