fix(op-wheel): record block base fee on its own gauge

RecordBlockStats set BlockGas twice — once with gas used and once with
the base fee — which left the BlockBaseFee gauge unset and clobbered the
gas gauge. Record the base fee on BlockBaseFee instead.

Also fix the pre-block status log, which emitted status.Gas for the
"basefee" field instead of status.BaseFee.

Adds a regression test asserting gas and base fee land on their own
gauges.

Closes #20958

Author: pjdurden

op-wheel/engine/engine.go

@@ -247,7 +247,7 @@ func Auto(
 					continue
 				}
 				log.Info("status", "head", status.Head, "safe", status.Safe, "finalized", status.Finalized,
-					"head_time", status.Head.Time, "txs", status.Txs, "gas", status.Gas, "basefee", status.Gas)
+					"head_time", status.Head.Time, "txs", status.Txs, "gas", status.Gas, "basefee", status.BaseFee)
 
 				// On a mocked "beacon epoch transition", update finalization and justification checkpoints.
 				// There are no gap slots, so we just go back 32 blocks.

op-wheel/engine/metrics.go

@@ -81,7 +81,7 @@ func (r *Metrics) RecordBlockStats(hash common.Hash, num uint64, time uint64, tx
 	r.BlockTime.Set(float64(time))
 	r.BlockTxs.Set(float64(txs))
 	r.BlockGas.Set(float64(gas))
-	r.BlockGas.Set(float64(baseFee))
+	r.BlockBaseFee.Set(baseFee)
 }
 
 var _ Metricer = (*Metrics)(nil)

op-wheel/engine/metrics_test.go

@@ -0,0 +1,32 @@
+package engine
+
+import (
+	"testing"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/prometheus/client_golang/prometheus"
+	dto "github.com/prometheus/client_model/go"
+	"github.com/stretchr/testify/require"
+)
+
+func gaugeValue(t *testing.T, g prometheus.Gauge) float64 {
+	t.Helper()
+	var m dto.Metric
+	require.NoError(t, g.Write(&m))
+	return m.GetGauge().GetValue()
+}
+
+// TestRecordBlockStats ensures gas and base fee are recorded on their own
+// gauges. Distinct values are used so a regression that records the base fee
+// onto the gas gauge (or leaves the base-fee gauge unset) is caught.
+func TestRecordBlockStats(t *testing.T) {
+	m := NewMetrics("test", prometheus.NewRegistry())
+
+	const gas = uint64(21000)
+	const baseFee = float64(1234)
+
+	m.RecordBlockStats(common.Hash{0x01}, 5, 100, 3, gas, baseFee)
+
+	require.Equal(t, float64(gas), gaugeValue(t, m.BlockGas), "BlockGas should record gas used")
+	require.Equal(t, baseFee, gaugeValue(t, m.BlockBaseFee), "BlockBaseFee should record the block base fee")
+}