fix: check for `decimals` method in transferredTokens (#748)

Previously we were looking for `decimals` hash in the contract `code`.
There are some contracts like USDC who happen to be behind a FiatTokenProxy, making it upgradable.
By directly calling the `decimals()` method, we interact with the contract and can be sure that the `decimals()` method is present.

fixes #678

src/logic/tokens/store/actions/fetchTokens.js

@@ -12,8 +12,7 @@ import { fetchTokenList } from '~/logic/tokens/api'
 import { type TokenProps, makeToken } from '~/logic/tokens/store/model/token'
 import { tokensSelector } from '~/logic/tokens/store/selectors'
 import { getWeb3 } from '~/logic/wallets/getWeb3'
-import { type GlobalState } from '~/store'
-import { store } from '~/store/index'
+import { type GlobalState, store } from '~/store'
 import { ensureOnce } from '~/utils/singleton'
 
 const createStandardTokenContract = async () => {

src/logic/tokens/utils/tokenHelpers.js

@@ -1,4 +1,5 @@
 // @flow
+import ERC20Detailed from '@openzeppelin/contracts/build/contracts/ERC20Detailed.json'
 import { List } from 'immutable'
 
 import logo from '~/assets/icons/icon_etherTokens.svg'
@@ -56,6 +57,17 @@ export const isAddressAToken = async (tokenAddress: string) => {
   return call !== '0x'
 }
 
+export const hasDecimalsMethod = async (address: string): Promise<boolean> => {
+  try {
+    const web3 = getWeb3()
+    const token = new web3.eth.Contract(ERC20Detailed.abi, address)
+    await token.methods.decimals().call()
+    return true
+  } catch (e) {
+    return false
+  }
+}
+
 export const isTokenTransfer = (data: string, value: number): boolean =>
   !!data && data.substring(0, 10) === '0xa9059cbb' && value === 0
 

src/routes/safe/store/actions/fetchTransactions.js

@@ -15,8 +15,8 @@ import { getLocalSafe } from '~/logic/safe/utils'
 import { getTokenInfos } from '~/logic/tokens/store/actions/fetchTokens'
 import { ALTERNATIVE_TOKEN_ABI } from '~/logic/tokens/utils/alternativeAbi'
 import {
-  DECIMALS_METHOD_HASH,
   SAFE_TRANSFER_FROM_WITHOUT_DATA_HASH,
+  hasDecimalsMethod,
   isMultisendTransaction,
   isTokenTransfer,
   isUpgradeTransaction,
@@ -102,7 +102,7 @@ export const buildTransactionFrom = async (safeAddress: string, tx: TxServiceMod
   const code = tx.to ? await web3.eth.getCode(tx.to) : ''
   const isERC721Token =
     code.includes(SAFE_TRANSFER_FROM_WITHOUT_DATA_HASH) ||
-    (isTokenTransfer(tx.data, Number(tx.value)) && !code.includes(DECIMALS_METHOD_HASH))
+    (isTokenTransfer(tx.data, Number(tx.value)) && !(await hasDecimalsMethod(tx.to)))
   const isSendTokenTx = !isERC721Token && isTokenTransfer(tx.data, Number(tx.value))
   const isMultiSendTx = isMultisendTransaction(tx.data, Number(tx.value))
   const isUpgradeTx = isMultiSendTx && isUpgradeTransaction(tx.data)