op-program: Pass a ChainConfig to the Config struct rather than a file path to load from

op-program/host/config/config.go

 package config
 
 import (
+	"encoding/json"
 	"errors"
+	"fmt"
+	"os"
 
 	opnode "github.com/ethereum-optimism/optimism/op-node"
 	"github.com/ethereum-optimism/optimism/op-node/rollup"
 	"github.com/ethereum-optimism/optimism/op-node/sources"
 	"github.com/ethereum-optimism/optimism/op-program/host/flags"
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core"
+	"github.com/ethereum/go-ethereum/params"
 	"github.com/urfave/cli"
 )
 
@@ -22,16 +27,24 @@ var (
 )
 
 type Config struct {
-	Rollup        *rollup.Config
-	DataDir       string
-	L2URL         string
-	L2GenesisPath string
-	L1Head        common.Hash
-	L2Head        common.Hash
-	L2Claim       common.Hash
-	L1URL         string
-	L1TrustRPC    bool
-	L1RPCKind     sources.RPCProviderKind
+	Rollup *rollup.Config
+	// DataDir is the directory to read/write pre-image data from/to.
+	//If not set, an in-memory key-value store is used and fetching data must be enabled
+	DataDir string
+
+	// L1Head is the block has of the L1 chain head block
+	L1Head     common.Hash
+	L1URL      string
+	L1TrustRPC bool
+	L1RPCKind  sources.RPCProviderKind
+
+	// L2Head is the agreed L2 block to start derivation from
+	L2Head common.Hash
+	L2URL  string
+	// L2Claim is the claimed L2 output root to verify
+	L2Claim common.Hash
+	// L2ChainConfig is the op-geth chain config for the L2 execution engine
+	L2ChainConfig *params.ChainConfig
 }
 
 func (c *Config) Check() error {
@@ -50,7 +63,7 @@ func (c *Config) Check() error {
 	if c.L2Claim == (common.Hash{}) {
 		return ErrInvalidL2Claim
 	}
-	if c.L2GenesisPath == "" {
+	if c.L2ChainConfig == nil {
 		return ErrMissingL2Genesis
 	}
 	if (c.L1URL != "") != (c.L2URL != "") {
@@ -67,10 +80,10 @@ func (c *Config) FetchingEnabled() bool {
 }
 
 // NewConfig creates a Config with all optional values set to the CLI default value
-func NewConfig(rollupCfg *rollup.Config, l2GenesisPath string, l1Head common.Hash, l2Head common.Hash, l2Claim common.Hash) *Config {
+func NewConfig(rollupCfg *rollup.Config, l2Genesis *params.ChainConfig, l1Head common.Hash, l2Head common.Hash, l2Claim common.Hash) *Config {
 	return &Config{
 		Rollup:        rollupCfg,
-		L2GenesisPath: l2GenesisPath,
+		L2ChainConfig: l2Genesis,
 		L1Head:        l1Head,
 		L2Head:        l2Head,
 		L2Claim:       l2Claim,
@@ -98,11 +111,16 @@ func NewConfigFromCLI(ctx *cli.Context) (*Config, error) {
 	if l1Head == (common.Hash{}) {
 		return nil, ErrInvalidL1Head
 	}
+	l2GenesisPath := ctx.GlobalString(flags.L2GenesisPath.Name)
+	l2ChainConfig, err := loadChainConfigFromGenesis(l2GenesisPath)
+	if err != nil {
+		return nil, fmt.Errorf("invalid genesis: %w", err)
+	}
 	return &Config{
 		Rollup:        rollupCfg,
 		DataDir:       ctx.GlobalString(flags.DataDir.Name),
 		L2URL:         ctx.GlobalString(flags.L2NodeAddr.Name),
-		L2GenesisPath: ctx.GlobalString(flags.L2GenesisPath.Name),
+		L2ChainConfig: l2ChainConfig,
 		L2Head:        l2Head,
 		L2Claim:       l2Claim,
 		L1Head:        l1Head,
@@ -111,3 +129,16 @@ func NewConfigFromCLI(ctx *cli.Context) (*Config, error) {
 		L1RPCKind:     sources.RPCProviderKind(ctx.GlobalString(flags.L1RPCProviderKind.Name)),
 	}, nil
 }
+
+func loadChainConfigFromGenesis(path string) (*params.ChainConfig, error) {
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return nil, fmt.Errorf("read l2 genesis file: %w", err)
+	}
+	var genesis core.Genesis
+	err = json.Unmarshal(data, &genesis)
+	if err != nil {
+		return nil, fmt.Errorf("parse l2 genesis file: %w", err)
+	}
+	return genesis.Config, nil
+}

op-program/host/config/config_test.go

@@ -6,11 +6,12 @@ import (
 	"github.com/ethereum-optimism/optimism/op-node/chaincfg"
 	"github.com/ethereum-optimism/optimism/op-node/rollup"
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/params"
 	"github.com/stretchr/testify/require"
 )
 
 var validRollupConfig = &chaincfg.Goerli
-var validL2GenesisPath = "genesis.json"
+var validL2Genesis = params.GoerliChainConfig
 var validL1Head = common.Hash{0xaa}
 var validL2Head = common.Hash{0xbb}
 var validL2Claim = common.Hash{0xcc}
@@ -60,7 +61,7 @@ func TestL2ClaimRequired(t *testing.T) {
 
 func TestL2GenesisRequired(t *testing.T) {
 	config := validConfig()
-	config.L2GenesisPath = ""
+	config.L2ChainConfig = nil
 	err := config.Check()
 	require.ErrorIs(t, err, ErrMissingL2Genesis)
 }
@@ -132,7 +133,7 @@ func TestRequireDataDirInNonFetchingMode(t *testing.T) {
 }
 
 func validConfig() *Config {
-	cfg := NewConfig(validRollupConfig, validL2GenesisPath, validL1Head, validL2Head, validL2Claim)
+	cfg := NewConfig(validRollupConfig, validL2Genesis, validL1Head, validL2Head, validL2Claim)
 	cfg.DataDir = "/tmp/configTest"
 	return cfg
 }

op-program/host/l2/l2.go

@@ -2,25 +2,17 @@ package l2
 
 import (
 	"context"
-	"encoding/json"
 	"fmt"
-	"os"
 
 	cll2 "github.com/ethereum-optimism/optimism/op-program/client/l2"
 	"github.com/ethereum-optimism/optimism/op-program/host/config"
 	"github.com/ethereum-optimism/optimism/op-program/preimage"
-	"github.com/ethereum/go-ethereum/core"
 	"github.com/ethereum/go-ethereum/log"
-	"github.com/ethereum/go-ethereum/params"
 )
 
 func NewEngine(logger log.Logger, pre preimage.Oracle, hint preimage.Hinter, cfg *config.Config) (*cll2.OracleEngine, error) {
 	oracle := cll2.NewCachingOracle(cll2.NewPreimageOracle(pre, hint))
-	genesis, err := loadL2Genesis(cfg)
-	if err != nil {
-		return nil, err
-	}
-	engineBackend, err := cll2.NewOracleBackedL2Chain(logger, oracle, genesis, cfg.L2Head)
+	engineBackend, err := cll2.NewOracleBackedL2Chain(logger, oracle, cfg.L2ChainConfig, cfg.L2Head)
 	if err != nil {
 		return nil, fmt.Errorf("create l2 chain: %w", err)
 	}
@@ -34,16 +26,3 @@ func NewFetchingOracle(ctx context.Context, logger log.Logger, cfg *config.Confi
 	}
 	return oracle, nil
 }
-
-func loadL2Genesis(cfg *config.Config) (*params.ChainConfig, error) {
-	data, err := os.ReadFile(cfg.L2GenesisPath)
-	if err != nil {
-		return nil, fmt.Errorf("read l2 genesis file: %w", err)
-	}
-	var genesis core.Genesis
-	err = json.Unmarshal(data, &genesis)
-	if err != nil {
-		return nil, fmt.Errorf("parse l2 genesis file: %w", err)
-	}
-	return genesis.Config, nil
-}