rpc: implement eth_coinbase (#325)

* rpc: implement eth_coinbase

* changelog

* address comments from review

* changelog

rpc/backend.go

@@ -47,13 +47,15 @@ func NewEthermintBackend(cliCtx context.CLIContext) *EthermintBackend {
 
 // BlockNumber returns the current block number.
 func (e *EthermintBackend) BlockNumber() (hexutil.Uint64, error) {
-	res, _, err := e.cliCtx.QueryWithData(fmt.Sprintf("custom/%s/blockNumber", types.ModuleName), nil)
+	res, height, err := e.cliCtx.QueryWithData(fmt.Sprintf("custom/%s/blockNumber", types.ModuleName), nil)
 	if err != nil {
 		return hexutil.Uint64(0), err
 	}
 
 	var out types.QueryResBlockNumber
 	e.cliCtx.Codec.MustUnmarshalJSON(res, &out)
+
+	e.cliCtx.WithHeight(height)
 	return hexutil.Uint64(out.Number), nil
 }
 

rpc/eth_api.go

@@ -90,9 +90,19 @@ func (e *PublicEthAPI) Syncing() (interface{}, error) {
 	}, nil
 }
 
-// Coinbase returns this node's coinbase address. Not used in Ethermint.
-func (e *PublicEthAPI) Coinbase() (addr common.Address) {
-	return
+// Coinbase is the address that staking rewards will be send to (alias for Etherbase).
+func (e *PublicEthAPI) Coinbase() (common.Address, error) {
+	node, err := e.cliCtx.GetNode()
+	if err != nil {
+		return common.Address{}, err
+	}
+
+	status, err := node.Status()
+	if err != nil {
+		return common.Address{}, err
+	}
+
+	return common.BytesToAddress(status.ValidatorInfo.Address.Bytes()), nil
 }
 
 // Mining returns whether or not this node is currently mining. Always false.