feat: added rpc method to deal ERC20 tokens (#10495)

* wip

* wip

* wip

* wip

* call + storage

* type fix

* wip

* wip

* smol fix

* cleanup

* cleanup

* cleanup

* cleanup

* chore: pedantic touchups

---------

Co-authored-by: Matthias Seitz <[email protected]>

Author: Soubhik-10

crates/anvil/core/src/eth/mod.rs

@@ -363,6 +363,15 @@ pub enum EthRequest {
     #[serde(rename = "anvil_setBalance", alias = "hardhat_setBalance")]
     SetBalance(Address, #[serde(deserialize_with = "deserialize_number")] U256),
 
+    /// Modifies the ERC20 balance of an account.
+    #[serde(
+        rename = "anvil_dealERC20",
+        alias = "hardhat_dealERC20",
+        alias = "anvil_setERC20Balance",
+        alias = "tenderly_setErc20Balance"
+    )]
+    DealERC20(Address, Address, #[serde(deserialize_with = "deserialize_number")] U256),
+
     /// Sets the code of a contract
     #[serde(rename = "anvil_setCode", alias = "hardhat_setCode")]
     SetCode(Address, Bytes),

crates/anvil/src/eth/api.rs

@@ -56,7 +56,7 @@ use alloy_rpc_types::{
     },
     request::TransactionRequest,
     simulate::{SimulatePayload, SimulatedBlock},
-    state::EvmOverrides,
+    state::{AccountOverride, EvmOverrides, StateOverridesBuilder},
     trace::{
         filter::TraceFilter,
         geth::{GethDebugTracingCallOptions, GethDebugTracingOptions, GethTrace},
@@ -67,6 +67,7 @@ use alloy_rpc_types::{
     EIP1186AccountProofResponse, FeeHistory, Filter, FilteredParams, Index, Log, Work,
 };
 use alloy_serde::WithOtherFields;
+use alloy_sol_types::{sol, SolCall, SolValue};
 use alloy_transport::TransportErrorKind;
 use anvil_core::{
     eth::{
@@ -355,6 +356,9 @@ impl EthApi {
             EthRequest::SetBalance(addr, val) => {
                 self.anvil_set_balance(addr, val).await.to_rpc_result()
             }
+            EthRequest::DealERC20(addr, token_addr, val) => {
+                self.anvil_deal_erc20(addr, token_addr, val).await.to_rpc_result()
+            }
             EthRequest::SetCode(addr, code) => {
                 self.anvil_set_code(addr, code).await.to_rpc_result()
             }
@@ -1852,6 +1856,76 @@ impl EthApi {
         Ok(())
     }
 
+    /// Deals ERC20 tokens to a address
+    ///
+    /// Handler for RPC call: `anvil_dealERC20`
+    pub async fn anvil_deal_erc20(
+        &self,
+        address: Address,
+        token_address: Address,
+        balance: U256,
+    ) -> Result<()> {
+        node_info!("anvil_dealERC20");
+
+        sol! {
+            #[sol(rpc)]
+            contract IERC20 {
+                function balanceOf(address target) external view returns (uint256);
+            }
+        }
+
+        let calldata = IERC20::balanceOfCall { target: address }.abi_encode();
+        let tx = TransactionRequest::default().with_to(token_address).with_input(calldata.clone());
+
+        // first collect all the slots that are used by the balanceOf call
+        let access_list_result =
+            self.create_access_list(WithOtherFields::new(tx.clone()), None).await?;
+        let access_list = access_list_result.access_list;
+
+        // now we can iterate over all the accessed slots and try to find the one that contains the
+        // balance by overriding the slot and checking the `balanceOfCall` of
+        for item in access_list.0 {
+            if item.address != token_address {
+                continue;
+            };
+            for slot in &item.storage_keys {
+                let account_override = AccountOverride::default()
+                    .with_state_diff(std::iter::once((*slot, B256::from(balance.to_be_bytes()))));
+
+                let state_override = StateOverridesBuilder::default()
+                    .append(token_address, account_override)
+                    .build();
+
+                let evm_override = EvmOverrides::state(Some(state_override));
+
+                let Ok(result) =
+                    self.call(WithOtherFields::new(tx.clone()), None, evm_override).await
+                else {
+                    // overriding this slot failed
+                    continue;
+                };
+
+                let Ok(result_balance) = U256::abi_decode(&result) else {
+                    // response returned something other than a U256
+                    continue;
+                };
+
+                if result_balance == balance {
+                    self.anvil_set_storage_at(
+                        token_address,
+                        U256::from_be_bytes(slot.0),
+                        B256::from(balance.to_be_bytes()),
+                    )
+                    .await?;
+                    return Ok(());
+                }
+            }
+        }
+
+        // unable to set the balance
+        Err(BlockchainError::Message("Unable to set ERC20 balance, no slot found".to_string()))
+    }
+
     /// Sets the code of a contract.
     ///
     /// Handler for RPC call: `anvil_setCode`

crates/anvil/tests/it/fork.rs

@@ -1465,6 +1465,31 @@ async fn test_reset_dev_account_nonce() {
     assert!(receipt.status());
 }
 
+#[tokio::test(flavor = "multi_thread")]
+async fn test_set_erc20_balance() {
+    let config: NodeConfig = fork_config();
+    let address = config.genesis_accounts[0].address();
+    let (api, handle) = spawn(config).await;
+
+    let provider = handle.http_provider();
+
+    alloy_sol_types::sol! {
+       #[sol(rpc)]
+       contract ERC20 {
+            function balanceOf(address owner) public view returns (uint256);
+       }
+    }
+    let dai = address!("0x6B175474E89094C44Da98b954EedeAC495271d0F");
+    let erc20 = ERC20::new(dai, provider);
+    let value = U256::from(500);
+
+    api.anvil_deal_erc20(address, dai, value).await.unwrap();
+
+    let new_balance = erc20.balanceOf(address).call().await.unwrap();
+
+    assert_eq!(new_balance, value);
+}
+
 #[tokio::test(flavor = "multi_thread")]
 async fn test_reset_updates_cache_path_when_rpc_url_not_provided() {
     let config: NodeConfig = fork_config();