rpc: implement eth_coinbase

CHANGELOG.md

@@ -61,6 +61,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
   * Remove evm `CodeKey` and `BlockKey`in favor of a prefix `Store`.
   * Set `BlockBloom` during `EndBlock` instead of `BeginBlock`.
   * `Commit` state object and `Finalize` storage after `InitGenesis` setup.
+* (rpc) [\#325](https://github.com/ChainSafe/ethermint/pull/325) `eth_coinbase` JSON-RPC query now returns the block proposer's validator address.
 
 ### Features
 

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 +90,20 @@ 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) {
+	height, err := e.BlockNumber()
+	if err != nil {
+		return common.Address{}, err
+	}
+	blockNumber := int64(height)
+
+	block, err := e.cliCtx.Client.Block(&blockNumber)
+	if err != nil {
+		return common.Address{}, err
+	}
+
+	return common.BytesToAddress(block.Block.ProposerAddress.Bytes()), nil
 }
 
 // Mining returns whether or not this node is currently mining. Always false.

tests/rpc_test.go

@@ -139,6 +139,18 @@ func TestEth_blockNumber(t *testing.T) {
 	t.Logf("Got block number: %s\n", res.String())
 }
 
+func TestEth_coinbase(t *testing.T) {
+	zeroAddress := hexutil.Bytes(ethcmn.Address{}.Bytes())
+	rpcRes := call(t, "eth_coinbase", []string{})
+
+	var res hexutil.Bytes
+	err := res.UnmarshalJSON(rpcRes.Result)
+	require.NoError(t, err)
+
+	t.Logf("Got coinbase block proposer: %s\n", res.String())
+	require.NotEqual(t, zeroAddress.String(), res.String(), "expected: %s got: %s\n", zeroAddress.String(), res.String())
+}
+
 func TestEth_GetBalance(t *testing.T) {
 	rpcRes := call(t, "eth_getBalance", []string{addrA, zeroString})