init: add random chain-id generator (#797)

* init: add random chain-id generator

* Update types/chain_id.go

Co-authored-by: Federico Kunze <31522760+fedekunze@users.noreply.github.com>
Co-authored-by: Alessio Treglia <alessio@tendermint.com>

client/config.go

@@ -61,3 +61,23 @@ func ValidateChainID(baseCmd *cobra.Command) *cobra.Command {
 	baseCmd.RunE = validateFn
 	return baseCmd
 }
+
+// GenerateChainID wraps a cobra command with a RunE function with base 10 integer chain-id random generation
+// when a chain-id is not provided.
+func GenerateChainID(baseCmd *cobra.Command) *cobra.Command {
+	// Copy base run command to be used after chain verification
+	baseRunE := baseCmd.RunE
+
+	// Function to replace command's RunE function
+	generateFn := func(cmd *cobra.Command, args []string) error {
+		chainID := viper.GetString(flags.FlagChainID)
+
+		if chainID == "" {
+			viper.Set(flags.FlagChainID, ethermint.GenerateRandomChainID())
+		}
+		return baseRunE(cmd, args)
+	}
+
+	baseCmd.RunE = generateFn
+	return baseCmd
+}

cmd/ethermintd/main.go

@@ -65,9 +65,11 @@ func main() {
 	}
 	// CLI commands to initialize the chain
 	rootCmd.AddCommand(
+		client.GenerateChainID(
 			client.ValidateChainID(
 				genutilcli.InitCmd(ctx, cdc, app.ModuleBasics, app.DefaultNodeHome),
 			),
+		),
 		genutilcli.CollectGenTxsCmd(ctx, cdc, auth.GenesisAccountIterator{}, app.DefaultNodeHome),
 		genutilcli.MigrateGenesisCmd(ctx, cdc),
 		genutilcli.GenTxCmd(

types/chain_id.go

@@ -7,6 +7,7 @@ import (
 	"strings"
 
 	sdkerrors "github.com/cosmos/cosmos-sdk/types/errors"
+	tmrand "github.com/tendermint/tendermint/libs/rand"
 )
 
 var (
@@ -46,3 +47,8 @@ func ParseChainID(chainID string) (*big.Int, error) {
 
 	return chainIDInt, nil
 }
+
+// GenerateRandomChainID returns a random chain-id in the valid format.
+func GenerateRandomChainID() string {
+	return fmt.Sprintf("ethermint-%d", 10+tmrand.Intn(10000))
+}