rpc: support fetching pending nonce (#191)

* consider mempool tx when computing account nonce

* fix lint

* add condition on blocknbr

* add log

* update changelog
:

* cleanup

CHANGELOG.md

@@ -60,6 +60,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 * (evm) [tharsis#24](https://github.com/tharsis/ethermint/pull/24) Implement metrics for `MsgEthereumTx`, state transitions, `BeginBlock` and `EndBlock`.
 * (rpc)  [#124](https://github.com/tharsis/ethermint/issues/124) Implement `txpool_content`, `txpool_inspect` and `txpool_status` RPC methods
 * (rpc) [tharsis#112](https://github.com/tharsis/ethermint/pull/153) Fix `eth_coinbase` to return the ethereum address of the validator
+* (rpc) [tharsis#176](https://github.com/tharsis/ethermint/issues/176) Support fetching pending nonce
 
 ### Bug Fixes
 

ethereum/rpc/namespaces/eth/api.go

@@ -256,7 +256,8 @@ func (e *PublicAPI) GetTransactionCount(address common.Address, blockNum rpctype
 		return &n, nil
 	}
 
-	_, nonce, err := accRet.GetAccountNumberSequence(e.clientCtx, from)
+	includePending := blockNum == rpctypes.EthPendingBlockNumber
+	nonce, err := getAccountNonce(e.clientCtx, e.backend, address, includePending, e.logger)
 	if err != nil {
 		return nil, err
 	}
@@ -565,16 +566,12 @@ func (e *PublicAPI) doCall(
 		accessList = args.AccessList
 	}
 
-	// Set destination address for call
-	var fromAddr sdk.AccAddress
-	if args.From != nil {
-		fromAddr = sdk.AccAddress(args.From.Bytes())
-	} else {
-		fromAddr = sdk.AccAddress(common.Address{}.Bytes())
+	if args.From == nil {
 		args.From = &common.Address{}
 	}
 
-	_, seq, err := e.clientCtx.AccountRetriever.GetAccountNumberSequence(e.clientCtx, fromAddr)
+	includePending := blockNr == rpctypes.EthPendingBlockNumber
+	seq, err := getAccountNonce(e.clientCtx, e.backend, *args.From, includePending, e.logger)
 	if err != nil {
 		return nil, err
 	}
@@ -1018,9 +1015,6 @@ func (e *PublicAPI) GetProof(address common.Address, storageKeys []string, block
 // provided on the args
 func (e *PublicAPI) setTxDefaults(args rpctypes.SendTxArgs) (rpctypes.SendTxArgs, error) {
 
-	// Get nonce (sequence) from sender account
-	from := sdk.AccAddress(args.From.Bytes())
-
 	if args.GasPrice == nil {
 		// TODO: Change to either:
 		// - min gas price from context once available through server/daemon, or
@@ -1031,7 +1025,7 @@ func (e *PublicAPI) setTxDefaults(args rpctypes.SendTxArgs) (rpctypes.SendTxArgs
 	if args.Nonce == nil {
 		// get the nonce from the account retriever
 		// ignore error in case tge account doesn't exist yet
-		_, nonce, _ := e.clientCtx.AccountRetriever.GetAccountNumberSequence(e.clientCtx, from)
+		nonce, _ := getAccountNonce(e.clientCtx, e.backend, args.From, true, e.logger)
 		args.Nonce = (*hexutil.Uint64)(&nonce)
 	}
 
@@ -1084,3 +1078,40 @@ func (e *PublicAPI) setTxDefaults(args rpctypes.SendTxArgs) (rpctypes.SendTxArgs
 
 	return args, nil
 }
+
+// getAccountNonce returns the account nonce for the given account address.
+// If the pending value is true, it will iterate over the mempool (pending)
+// txs in order to compute and return the pending tx sequence.
+// Todo: include the ability to specify a blockNumber
+func getAccountNonce(ctx client.Context, backend backend.Backend, accAddr common.Address, pending bool, logger log.Logger) (uint64, error) {
+	_, nonce, err := ctx.AccountRetriever.GetAccountNumberSequence(ctx, accAddr.Bytes())
+	if err != nil {
+		return 0, err
+	}
+
+	if !pending {
+		return nonce, nil
+	}
+
+	// the account retriever doesn't include the uncommitted transactions on the nonce so we need to
+	// to manually add them.
+	pendingTxs, err := backend.PendingTransactions()
+	if err != nil {
+		logger.Errorln("fails to fetch pending transactions")
+		return nonce, nil
+	}
+
+	// add the uncommitted txs to the nonce counter
+	if len(pendingTxs) != 0 {
+		for i := range pendingTxs {
+			if pendingTxs[i] == nil {
+				continue
+			}
+			if pendingTxs[i].From == accAddr {
+				nonce++
+			}
+		}
+	}
+
+	return nonce, nil
+}