feat: `rollup gasPrices` RPC endpoint (#1136)

* feature: l2geth  endpoint

* chore: add changeset
Co-authored-by: Liam Horne <liam@lihorne.com>

.changeset/little-badgers-hammer.md

+---
+'@eth-optimism/integration-tests': patch
+'@eth-optimism/l2geth': patch
+---
+
+Add new RPC endpoint `rollup_gasPrices`

integration-tests/test/rpc.spec.ts

@@ -426,4 +426,15 @@ describe('Basic RPC tests', () => {
         .reverted
     })
   })
+
+  describe('rollup_gasPrices', () => {
+    it('should return the L1 and L2 gas prices', async () => {
+      const result = await provider.send('rollup_gasPrices', []);
+      const l1GasPrice = await env.l1Wallet.provider.getGasPrice()
+      const l2GasPrice = await env.gasPriceOracle.gasPrice()
+
+      expect(BigNumber.from(result.l1GasPrice)).to.deep.eq(l1GasPrice)
+      expect((BigNumber.from(result.l2GasPrice))).to.deep.eq(l2GasPrice)
+    })
+  })
 })

integration-tests/test/shared/env.ts

-import { getContractFactory } from '@eth-optimism/contracts'
+import { getContractFactory, predeploys } from '@eth-optimism/contracts'
 import { Watcher } from '@eth-optimism/core-utils'
 import { Contract, utils, Wallet } from 'ethers'
 import {
@@ -32,6 +32,7 @@ export class OptimismEnv {
   ovmEth: Contract
   l2Bridge: Contract
   l2Messenger: Contract
+  gasPriceOracle: Contract
 
   // The L1 <> L2 State watcher
   watcher: Watcher
@@ -47,6 +48,7 @@ export class OptimismEnv {
     this.ovmEth = args.ovmEth
     this.l2Bridge = args.l2Bridge
     this.l2Messenger = args.l2Messenger
+    this.gasPriceOracle = args.gasPriceOracle
     this.watcher = args.watcher
     this.l1Wallet = args.l1Wallet
     this.l2Wallet = args.l2Wallet
@@ -79,12 +81,17 @@ export class OptimismEnv {
       .connect(l1Wallet)
       .attach(ctcAddress)
 
+    const gasPriceOracle = getContractFactory('OVM_GasPriceOracle')
+      .connect(l2Wallet)
+      .attach(predeploys.OVM_GasPriceOracle)
+
     return new OptimismEnv({
       addressManager,
       l1Bridge,
       ctc,
       l1Messenger,
       ovmEth,
+      gasPriceOracle,
       l2Bridge,
       l2Messenger,
       watcher,

l2geth/internal/ethapi/api.go

@@ -1983,6 +1983,27 @@ func (api *PublicRollupAPI) GetInfo(ctx context.Context) rollupInfo {
 	}
 }
 
+type gasPrices struct {
+	L1GasPrice *hexutil.Big `json:"l1GasPrice"`
+	L2GasPrice *hexutil.Big `json:"l2GasPrice"`
+}
+
+// GasPrices returns the L1 and L2 gas price known by the node
+func (api *PublicRollupAPI) GasPrices(ctx context.Context) (*gasPrices, error) {
+	l1GasPrice, err := api.b.SuggestL1GasPrice(ctx)
+	if err != nil {
+		return nil, err
+	}
+	l2GasPrice, err := api.b.SuggestL2GasPrice(ctx)
+	if err != nil {
+		return nil, err
+	}
+	return &gasPrices{
+		L1GasPrice: (*hexutil.Big)(l1GasPrice),
+		L2GasPrice: (*hexutil.Big)(l2GasPrice),
+	}, nil
+}
+
 // PrivatelRollupAPI provides private RPC methods to control the sequencer.
 // These methods can be abused by external users and must be considered insecure for use by untrusted users.
 type PrivateRollupAPI struct {