fix: remove empty pending and future transaction lists (#4987)

.changeset/thick-cycles-attend.md

@@ -0,0 +1,5 @@
+---
+"@nomicfoundation/edr": patch
+---
+
+Fixed a bug in `hardhat_dropTransaction` where empty queues persisted and caused panics

crates/edr_evm/src/mempool.rs

@@ -335,6 +335,10 @@ impl MemPool {
                     let mut invalidated_transactions = pending_transactions.split_off(idx + 1);
                     let removed = pending_transactions.remove(idx);
 
+                    if pending_transactions.is_empty() {
+                        self.pending_transactions.remove(caller);
+                    }
+
                     self.future_transactions
                         .entry(*caller)
                         .and_modify(|transactions| {
@@ -352,7 +356,13 @@ impl MemPool {
                     .enumerate()
                     .find(|(_, transaction)| *transaction.hash() == *hash)
                 {
-                    return Some(future_transactions.remove(idx));
+                    let removed = future_transactions.remove(idx);
+
+                    if future_transactions.is_empty() {
+                        self.future_transactions.remove(caller);
+                    }
+
+                    return Some(removed);
                 }
             }
         }

crates/edr_provider/tests/issue_325.rs

@@ -0,0 +1,65 @@
+use edr_eth::{
+    remote::PreEip1898BlockSpec, transaction::EthTransactionRequest, AccountInfo, Address, SpecId,
+    B256,
+};
+use edr_evm::KECCAK_EMPTY;
+use edr_provider::{
+    test_utils::{create_test_config_with_fork, one_ether},
+    MethodInvocation, MiningConfig, NoopLogger, Provider, ProviderRequest,
+};
+use tokio::runtime;
+
+#[tokio::test(flavor = "multi_thread")]
+async fn issue_325() -> anyhow::Result<()> {
+    let logger = Box::new(NoopLogger);
+    let subscriber = Box::new(|_event| {});
+
+    let mut config = create_test_config_with_fork(None);
+    config.hardfork = SpecId::CANCUN;
+    config.mining = MiningConfig {
+        auto_mine: false,
+        ..MiningConfig::default()
+    };
+
+    let impersonated_account = Address::random();
+    config.genesis_accounts.insert(
+        impersonated_account,
+        AccountInfo {
+            balance: one_ether(),
+            nonce: 0,
+            code: None,
+            code_hash: KECCAK_EMPTY,
+        },
+    );
+
+    let provider = Provider::new(runtime::Handle::current(), logger, subscriber, config)?;
+
+    provider.handle_request(ProviderRequest::Single(
+        MethodInvocation::ImpersonateAccount(impersonated_account.into()),
+    ))?;
+
+    let result = provider.handle_request(ProviderRequest::Single(
+        MethodInvocation::SendTransaction(EthTransactionRequest {
+            from: impersonated_account,
+            to: Some(Address::random()),
+            ..EthTransactionRequest::default()
+        }),
+    ))?;
+
+    let transaction_hash: B256 = serde_json::from_value(result.result)?;
+
+    let result = provider.handle_request(ProviderRequest::Single(
+        MethodInvocation::DropTransaction(transaction_hash),
+    ))?;
+
+    let dropped: bool = serde_json::from_value(result.result)?;
+
+    assert!(dropped);
+
+    provider.handle_request(ProviderRequest::Single(MethodInvocation::GetBlockByNumber(
+        PreEip1898BlockSpec::pending(),
+        false,
+    )))?;
+
+    Ok(())
+}