Merge pull request #535 from onflow:534-feature-restrict-token-decima…

…ls-on-bridge-to-cadence

Now allows 18 decimal places for EVM - EVM flow transfers. Restricts transfers to Cadence to 8 decimal places

src/background/service/openapi.ts

@@ -295,7 +295,8 @@ const defaultFlowToken = {
   },
   logoURI:
     'https://cdn.jsdelivr.net/gh/FlowFans/flow-token-list@main/token-registry/A.1654653399040a61.FlowToken/logo.svg',
-  decimals: 8,
+  // On Evm networks we can use up to 18 decimals
+  decimals: 18,
   symbol: 'flow',
 };
 

src/ui/reducers/__tests__/transaction-reducer.test.ts

@@ -1,11 +1,10 @@
 import { type TokenInfo } from 'flow-native-token-registry';
 import { describe, expect, it } from 'vitest';
 
-import { type Contact } from '@/shared/types/network-types';
 import {
   type NetworkType,
   type TokenType,
-  type TransactionStateString,
+  type TransactionState,
 } from '@/shared/types/transaction-types';
 import { type CoinItem, type WalletAddress } from '@/shared/types/wallet-types';
 
@@ -316,6 +315,71 @@ describe('Transaction Reducer', () => {
         // Should preserve trailing zeros for precision in crypto transactions
         expect(newState.amount).toBe('100.100000');
       });
+
+      describe('network decimals handling', () => {
+        it('should handle EVM to EVM transfers with up to 18 decimals', () => {
+          const stateWithEvmNetworks: TransactionState = {
+            ...stateWithBalance,
+            fromNetwork: 'Evm' as NetworkType,
+            toNetwork: 'Evm' as NetworkType,
+            selectedToken: {
+              ...stateWithBalance.selectedToken,
+              decimals: 18,
+            },
+            fiatOrCoin: 'coin',
+          };
+
+          const action = {
+            type: 'setAmount' as const,
+            payload: '1.123456789012345678', // 18 decimals
+          };
+
+          const newState = transactionReducer(stateWithEvmNetworks, action);
+          expect(newState.amount).toBe('1.123456789012345678');
+        });
+
+        it('should limit non-EVM transfers to 8 decimals', () => {
+          const stateWithMixedNetworks: TransactionState = {
+            ...stateWithBalance,
+            fromNetwork: 'Evm' as NetworkType,
+            toNetwork: 'Cadence' as NetworkType,
+            selectedToken: {
+              ...stateWithBalance.selectedToken,
+              decimals: 18,
+            },
+            fiatOrCoin: 'coin',
+          };
+
+          const action = {
+            type: 'setAmount' as const,
+            payload: '1.123456789012345678', // 18 decimals
+          };
+
+          const newState = transactionReducer(stateWithMixedNetworks, action);
+          expect(newState.amount).toBe('1.12345678'); // Should be truncated to 8 decimals
+        });
+
+        it('should respect token decimals even if less than network maximum', () => {
+          const stateWithLowDecimalToken: TransactionState = {
+            ...stateWithBalance,
+            fromNetwork: 'Evm' as NetworkType,
+            toNetwork: 'Evm' as NetworkType,
+            selectedToken: {
+              ...stateWithBalance.selectedToken,
+              decimals: 6,
+            },
+            fiatOrCoin: 'coin',
+          };
+
+          const action = {
+            type: 'setAmount' as const,
+            payload: '1.123456789012345678', // 18 decimals
+          };
+
+          const newState = transactionReducer(stateWithLowDecimalToken, action);
+          expect(newState.amount).toBe('1.123456'); // Should be truncated to 6 decimals
+        });
+      });
     });
 
     describe('setAmountToMax', () => {

src/ui/reducers/transaction-reducer.ts

@@ -222,8 +222,15 @@ export const transactionReducer = (
         // Calculate the remaining balance after the transaction
         remainingBalance = balance.minus(new BN(amountInCoin));
       } else if (state.fiatOrCoin === 'coin') {
+        // Should limit non-evm networks to 8 decimals
+        const maxNetworkDecimals =
+          state.fromNetwork === 'Evm' && state.toNetwork === 'Evm' ? 18 : 8;
         // Check if the amount entered has too many decimal places
-        amountInCoin = trimDecimalAmount(action.payload, state.selectedToken.decimals, 'entering');
+        amountInCoin = trimDecimalAmount(
+          action.payload,
+          Math.min(maxNetworkDecimals, state.selectedToken.decimals),
+          'entering'
+        );
 
         // Check if the balance is exceeded
         const amountBN = new BN(