fix: respect existing genesis file (#2868)

## Describe your changes and provide context
This PR is a followup for #2835 to handle a case where the user already
has their own genesis file and does not want to remove them or overwrite
them. Here is the slack comment by @masih that suggested this fix:
https://sei-network-io.slack.com/archives/C06A3D4FWE5/p1770833867974669?thread_ts=1770803742.497719&cid=C06A3D4FWE5

## Testing performed to validate your change

---------

Co-authored-by: Mojtaba <mojtaba@celestia.org>

Author: mojtaba-esk

cmd/seid/cmd/init.go

@@ -13,6 +13,7 @@ import (
 	"github.com/sei-protocol/sei-chain/app/params"
 	tmcfg "github.com/sei-protocol/sei-chain/sei-tendermint/config"
 	"github.com/sei-protocol/sei-chain/sei-tendermint/libs/cli"
+	"github.com/sei-protocol/sei-chain/sei-tendermint/libs/log"
 	tmos "github.com/sei-protocol/sei-chain/sei-tendermint/libs/os"
 	"github.com/sei-protocol/sei-chain/sei-tendermint/types"
 	"github.com/spf13/cobra"
@@ -21,6 +22,8 @@ import (
 	clientconfig "github.com/cosmos/cosmos-sdk/client/config"
 	"github.com/cosmos/cosmos-sdk/client/flags"
 	"github.com/cosmos/cosmos-sdk/client/input"
+	"github.com/cosmos/cosmos-sdk/codec"
+	"github.com/cosmos/cosmos-sdk/server"
 	srvconfig "github.com/cosmos/cosmos-sdk/server/config"
 	sdk "github.com/cosmos/cosmos-sdk/types"
 	"github.com/cosmos/cosmos-sdk/types/module"
@@ -141,46 +144,10 @@ func InitCmd(mbm module.BasicManager, defaultNodeHome string) *cobra.Command {
 
 			genFile := tmConfig.GenesisFile()
 			overwrite, _ := cmd.Flags().GetBool(FlagOverwrite)
-
-			if !overwrite && tmos.FileExists(genFile) {
-				return fmt.Errorf("genesis.json file already exists: %v", genFile)
-			}
-
-			var genDoc *types.GenesisDoc
-			var appState json.RawMessage
-			if genesis.IsWellKnown(chainID) {
-				var err error
-				genDoc, err = genesis.EmbeddedGenesisDoc(chainID)
-				if err != nil {
-					return errors.Wrapf(err, "failed to load embedded genesis for %s", chainID)
-				}
-				appState = genDoc.AppState
-			} else {
-				var err error
-				appState, err = json.MarshalIndent(mbm.DefaultGenesis(cdc), "", " ")
-				if err != nil {
-					return errors.Wrap(err, "Failed to marshall default genesis state")
-				}
-				genDoc = &types.GenesisDoc{}
-				if fi, err := os.Stat(genFile); err != nil {
-					if !os.IsNotExist(err) {
-						return err
-					}
-				} else {
-					if fi.IsDir() {
-						return fmt.Errorf("genesis path is a directory, not a file: %s", genFile)
-					}
-					genDoc, err = types.GenesisDocFromFile(genFile)
-					if err != nil {
-						return errors.Wrap(err, "Failed to read genesis doc from file")
-					}
-				}
-				genDoc.ChainID = chainID
-				genDoc.Validators = nil
-				genDoc.AppState = appState
-			}
-			if err = genutil.ExportGenesisFile(genDoc, genFile); err != nil {
-				return errors.Wrap(err, "Failed to export genesis file")
+			serverCtx := server.GetServerContextFromCmd(cmd)
+			genDoc, err := loadOrWriteGenesis(serverCtx.Logger, genFile, chainID, overwrite, mbm, cdc)
+			if err != nil {
+				return err
 			}
 
 			clientConfig, err := clientconfig.GetClientConfig(configPath, clientCtx.Viper)
@@ -191,7 +158,7 @@ func InitCmd(mbm module.BasicManager, defaultNodeHome string) *cobra.Command {
 				return err
 			}
 
-			toPrint := newPrintInfo(tmConfig.Moniker, chainID, nodeID, "", appState)
+			toPrint := newPrintInfo(tmConfig.Moniker, chainID, nodeID, "", genDoc.AppState)
 
 			// Write Tendermint config.toml
 			err = tmcfg.WriteConfigFile(tmConfig.RootDir, tmConfig)
@@ -233,3 +200,78 @@ func InitCmd(mbm module.BasicManager, defaultNodeHome string) *cobra.Command {
 
 	return cmd
 }
+
+// loadOrWriteGenesis loads existing genesis at genFile if present and !overwrite, else writes embedded (well-known) or default.
+func loadOrWriteGenesis(logger log.Logger, genFile, chainID string, overwrite bool, mbm module.BasicManager, cdc codec.JSONCodec) (*types.GenesisDoc, error) {
+	if !overwrite && tmos.FileExists(genFile) {
+		if err := ensureGenesisPathIsFile(genFile); err != nil {
+			return nil, err
+		}
+		genDoc, err := types.GenesisDocFromFile(genFile)
+		if err != nil {
+			return nil, errors.Wrapf(err, "failed to read genesis file %s", genFile)
+		}
+		if genDoc.ChainID != chainID {
+			return nil, fmt.Errorf("genesis file %s has chain_id %q but init chain-id is %q", genFile, genDoc.ChainID, chainID)
+		}
+		if logger != nil {
+			logger.Debug("using existing genesis file (not overwriting)", "path", genFile)
+		}
+		return genDoc, nil
+	}
+
+	if genesis.IsWellKnown(chainID) {
+		genDoc, err := genesis.EmbeddedGenesisDoc(chainID)
+		if err != nil {
+			return nil, errors.Wrapf(err, "failed to load embedded genesis for %s", chainID)
+		}
+		if logger != nil {
+			logger.Debug("writing genesis file (embedded)", "chain_id", chainID, "path", genFile)
+		}
+		if err := genutil.ExportGenesisFile(genDoc, genFile); err != nil {
+			return nil, errors.Wrap(err, "Failed to export genesis file")
+		}
+		return genDoc, nil
+	}
+
+	appState, err := json.MarshalIndent(mbm.DefaultGenesis(cdc), "", " ")
+	if err != nil {
+		return nil, errors.Wrap(err, "Failed to marshall default genesis state")
+	}
+	genDoc := &types.GenesisDoc{ChainID: chainID, AppState: appState}
+	if tmos.FileExists(genFile) {
+		if err := ensureGenesisPathIsFile(genFile); err != nil {
+			return nil, err
+		}
+		var err error
+		genDoc, err = types.GenesisDocFromFile(genFile)
+		if err != nil {
+			return nil, errors.Wrap(err, "Failed to read genesis doc from file")
+		}
+		genDoc.ChainID = chainID
+		genDoc.Validators = nil
+		genDoc.AppState = appState
+	}
+
+	if logger != nil {
+		logger.Debug("writing genesis file (default)", "chain_id", chainID, "path", genFile)
+	}
+	if err := genutil.ExportGenesisFile(genDoc, genFile); err != nil {
+		return nil, errors.Wrap(err, "Failed to export genesis file")
+	}
+	return genDoc, nil
+}
+
+func ensureGenesisPathIsFile(genFile string) error {
+	fi, err := os.Stat(genFile)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return nil
+		}
+		return errors.Wrapf(err, "failed to stat genesis file %s", genFile)
+	}
+	if fi.IsDir() {
+		return fmt.Errorf("genesis path is a directory, not a file: %s", genFile)
+	}
+	return nil
+}

cmd/seid/cmd/init_test.go

@@ -1,16 +1,21 @@
 package cmd
 
 import (
+	"encoding/json"
 	"fmt"
 	"os"
 	"path/filepath"
 	"testing"
 
 	srvconfig "github.com/cosmos/cosmos-sdk/server/config"
+	"github.com/sei-protocol/sei-chain/app"
+	"github.com/sei-protocol/sei-chain/app/genesis"
 	"github.com/sei-protocol/sei-chain/app/params"
 	evmrpcconfig "github.com/sei-protocol/sei-chain/evmrpc/config"
 	seidbconfig "github.com/sei-protocol/sei-chain/sei-db/config"
 	tmcfg "github.com/sei-protocol/sei-chain/sei-tendermint/config"
+	"github.com/sei-protocol/sei-chain/sei-tendermint/libs/log"
+	"github.com/sei-protocol/sei-chain/sei-tendermint/types"
 	"github.com/spf13/viper"
 	"github.com/stretchr/testify/require"
 )
@@ -230,3 +235,111 @@ func TestModeConfigurationMatrix(t *testing.T) {
 		})
 	}
 }
+
+// TestLoadOrWriteGenesis_ExplicitConfigWins: existing genesis + no overwrite leaves file unchanged.
+func TestLoadOrWriteGenesis_ExplicitConfigWins(t *testing.T) {
+	dir := t.TempDir()
+	genFile := filepath.Join(dir, "genesis.json")
+	const chainID = "atlantic-2"
+
+	// a minimal valid genesis with matching chain_id
+	existing := &types.GenesisDoc{ChainID: chainID, AppState: json.RawMessage(`{}`)}
+	err := existing.SaveAs(genFile)
+	require.NoError(t, err)
+	origContent, err := os.ReadFile(genFile)
+	require.NoError(t, err)
+
+	encCfg := app.MakeEncodingConfig()
+	genDoc, err := loadOrWriteGenesis(log.NewNopLogger(), genFile, chainID, false, app.ModuleBasics, encCfg.Marshaler)
+	require.NoError(t, err)
+	require.NotNil(t, genDoc)
+	require.Equal(t, chainID, genDoc.ChainID)
+
+	// File must be unchanged
+	afterContent, err := os.ReadFile(genFile)
+	require.NoError(t, err)
+	require.Equal(t, string(origContent), string(afterContent), "genesis file should not be overwritten")
+}
+
+// TestLoadOrWriteGenesis_WrongChainID: wrong chain_id in file returns error.
+func TestLoadOrWriteGenesis_WrongChainID(t *testing.T) {
+	dir := t.TempDir()
+	genFile := filepath.Join(dir, "genesis.json")
+	existing := &types.GenesisDoc{ChainID: "wrong-chain", AppState: json.RawMessage(`{}`)}
+	err := existing.SaveAs(genFile)
+	require.NoError(t, err)
+
+	encCfg := app.MakeEncodingConfig()
+	_, err = loadOrWriteGenesis(log.NewNopLogger(), genFile, "atlantic-2", false, app.ModuleBasics, encCfg.Marshaler)
+	require.Error(t, err)
+	require.Contains(t, err.Error(), "chain_id")
+}
+
+// TestLoadOrWriteGenesis_PathIsDirectory: path is directory returns error.
+func TestLoadOrWriteGenesis_PathIsDirectory(t *testing.T) {
+	dir := t.TempDir()
+	genFile := filepath.Join(dir, "genesis.json")
+	require.NoError(t, os.MkdirAll(genFile, 0755))
+
+	encCfg := app.MakeEncodingConfig()
+	_, err := loadOrWriteGenesis(log.NewNopLogger(), genFile, "atlantic-2", false, app.ModuleBasics, encCfg.Marshaler)
+	require.Error(t, err)
+	require.Contains(t, err.Error(), "directory")
+}
+
+// TestLoadOrWriteGenesis_WellKnownWritesEmbedded: well-known chain gets embedded genesis.
+func TestLoadOrWriteGenesis_WellKnownWritesEmbedded(t *testing.T) {
+	dir := t.TempDir()
+	genFile := filepath.Join(dir, "genesis.json")
+	const chainID = "atlantic-2"
+	require.True(t, genesis.IsWellKnown(chainID), "atlantic-2 should be well-known")
+	encCfg := app.MakeEncodingConfig()
+
+	genDoc, err := loadOrWriteGenesis(log.NewNopLogger(), genFile, chainID, false, app.ModuleBasics, encCfg.Marshaler)
+	require.NoError(t, err)
+	require.NotNil(t, genDoc)
+	require.Equal(t, chainID, genDoc.ChainID)
+	require.NotEmpty(t, genDoc.AppState)
+
+	embedded, err := genesis.EmbeddedGenesisDoc(chainID)
+	require.NoError(t, err)
+	require.Equal(t, embedded.ChainID, genDoc.ChainID)
+}
+
+// TestLoadOrWriteGenesis_OverwriteReplacesFile: overwrite=true replaces existing file.
+func TestLoadOrWriteGenesis_OverwriteReplacesFile(t *testing.T) {
+	dir := t.TempDir()
+	genFile := filepath.Join(dir, "genesis.json")
+	const chainID = "atlantic-2"
+	existing := &types.GenesisDoc{ChainID: chainID, AppState: json.RawMessage(`{"old":true}`)}
+	require.NoError(t, existing.SaveAs(genFile))
+
+	encCfg := app.MakeEncodingConfig()
+	genDoc, err := loadOrWriteGenesis(log.NewNopLogger(), genFile, chainID, true, app.ModuleBasics, encCfg.Marshaler)
+	require.NoError(t, err)
+	require.NotNil(t, genDoc)
+	// Should be overwritten
+	require.NotEqual(t, `{"old":true}`, string(genDoc.AppState))
+}
+
+// TestLoadOrWriteGenesis_UnknownChainWritesDefault: unknown chain gets default genesis.
+func TestLoadOrWriteGenesis_UnknownChainWritesDefault(t *testing.T) {
+	dir := t.TempDir()
+	genFile := filepath.Join(dir, "genesis.json")
+	const chainID = "custom-chain-1"
+	require.False(t, genesis.IsWellKnown(chainID), "custom-chain-1 should not be well-known")
+
+	encCfg := app.MakeEncodingConfig()
+	genDoc, err := loadOrWriteGenesis(log.NewNopLogger(), genFile, chainID, false, app.ModuleBasics, encCfg.Marshaler)
+	require.NoError(t, err)
+	require.NotNil(t, genDoc)
+	require.Equal(t, chainID, genDoc.ChainID)
+	require.NotEmpty(t, genDoc.AppState)
+
+	// Should contain known module keys
+	var state map[string]json.RawMessage
+	require.NoError(t, json.Unmarshal(genDoc.AppState, &state))
+	require.Contains(t, state, "bank")
+	require.Contains(t, state, "staking")
+	require.Contains(t, state, "genutil")
+}