op-chain-ops: better deploy config validation

Ensure that the `DeployConfig.Check` function checks for
the existence of the `L1StartingBlockTag`. This check was
previously being done outside of the `Check` function.
Also remove a check for the L2 genesis gas limit being
non zero since this is being done inside of `Check`.
Also add some better error messages in the case of bad
deploy config parsing.

op-chain-ops/genesis/config.go

@@ -109,6 +109,9 @@ type DeployConfig struct {
 
 // Check will ensure that the config is sane and return an error when it is not
 func (d *DeployConfig) Check() error {
+	if d.L1StartingBlockTag == nil {
+		return fmt.Errorf("%w: L2StartingBlockTag cannot be nil", ErrInvalidDeployConfig)
+	}
 	if d.L1ChainID == 0 {
 		return fmt.Errorf("%w: L1ChainID cannot be 0", ErrInvalidDeployConfig)
 	}
@@ -328,7 +331,7 @@ func NewDeployConfig(path string) (*DeployConfig, error) {
 
 	var config DeployConfig
 	if err := json.Unmarshal(file, &config); err != nil {
-		return nil, err
+		return nil, fmt.Errorf("cannot unmarshal deploy config: %w", err)
 	}
 
 	return &config, nil

op-node/cmd/genesis/cmd.go

@@ -3,7 +3,6 @@ package genesis
 import (
 	"context"
 	"encoding/json"
-	"errors"
 	"fmt"
 	"math/big"
 	"os"
@@ -114,16 +113,24 @@ var Subcommands = cli.Commands{
 				return err
 			}
 
-			if config.L1StartingBlockTag == nil {
-				return errors.New("must specify a starting block tag in genesis")
+			depPath, network := filepath.Split(ctx.String("deployment-dir"))
+			hh, err := hardhat.New(network, nil, []string{depPath})
+			if err != nil {
+				return err
+			}
+
+			// Read the appropriate deployment addresses from disk
+			if err := config.GetDeployedAddresses(hh); err != nil {
+				return err
 			}
-			if config.L2GenesisBlockGasLimit == 0 { // TODO: this is a hotfix, need to set default values in more clean way + sanity check the config
-				config.L2GenesisBlockGasLimit = 15_000_000
+			// Sanity check the config
+			if err := config.Check(); err != nil {
+				return err
 			}
 
 			client, err := ethclient.Dial(ctx.String("l1-rpc"))
 			if err != nil {
-				return err
+				return fmt.Errorf("cannot dial %s: %w", ctx.String("l1-rpc"), err)
 			}
 
 			var l1StartBlock *types.Block
@@ -136,20 +143,6 @@ var Subcommands = cli.Commands{
 				return fmt.Errorf("error getting l1 start block: %w", err)
 			}
 
-			depPath, network := filepath.Split(ctx.String("deployment-dir"))
-			hh, err := hardhat.New(network, nil, []string{depPath})
-			if err != nil {
-				return err
-			}
-
-			// Read the appropriate deployment addresses from disk
-			if err := config.GetDeployedAddresses(hh); err != nil {
-				return err
-			}
-			// Sanity check the config
-			if err := config.Check(); err != nil {
-				return err
-			}
 			// Build the developer L2 genesis block
 			l2Genesis, err := genesis.BuildL2DeveloperGenesis(config, l1StartBlock)
 			if err != nil {