p2p: expose SaveAs on NodeKey (#4981)

Closes #4681

CHANGELOG_PENDING.md

@@ -67,6 +67,7 @@ Friendly reminder, we have a [bug bounty program](https://hackerone.com/tendermi
 - [evidence] [\#4532](https://github.com/tendermint/tendermint/pull/4532) Handle evidence from light clients (@melekes)
 - [light] [\#4532](https://github.com/tendermint/tendermint/pull/4532) Submit conflicting headers, if any, to a full node & all witnesses (@melekes)
 - [rpc] [\#4532](https://github.com/tendermint/tendermint/pull/4923) Support `BlockByHash` query (@fedekunze)
+- [p2p] \#4981 Expose `SaveAs` func on NodeKey (@melekes)
 
 ### IMPROVEMENTS:
 

p2p/key.go

@@ -44,8 +44,8 @@ func PubKeyToID(pubKey crypto.PubKey) ID {
 	return ID(hex.EncodeToString(pubKey.Address()))
 }
 
-// LoadOrGenNodeKey attempts to load the NodeKey from the given filePath.
-// If the file does not exist, it generates and saves a new NodeKey.
+// LoadOrGenNodeKey attempts to load the NodeKey from the given filePath. If
+// the file does not exist, it generates and saves a new NodeKey.
 func LoadOrGenNodeKey(filePath string) (*NodeKey, error) {
 	if tmos.FileExists(filePath) {
 		nodeKey, err := LoadNodeKey(filePath)
@@ -54,9 +54,20 @@ func LoadOrGenNodeKey(filePath string) (*NodeKey, error) {
 		}
 		return nodeKey, nil
 	}
-	return genNodeKey(filePath)
+
+	privKey := ed25519.GenPrivKey()
+	nodeKey := &NodeKey{
+		PrivKey: privKey,
+	}
+
+	if err := nodeKey.SaveAs(filePath); err != nil {
+		return nil, err
+	}
+
+	return nodeKey, nil
 }
 
+// LoadNodeKey loads NodeKey located in filePath.
 func LoadNodeKey(filePath string) (*NodeKey, error) {
 	jsonBytes, err := ioutil.ReadFile(filePath)
 	if err != nil {
@@ -65,26 +76,22 @@ func LoadNodeKey(filePath string) (*NodeKey, error) {
 	nodeKey := new(NodeKey)
 	err = cdc.UnmarshalJSON(jsonBytes, nodeKey)
 	if err != nil {
-		return nil, fmt.Errorf("error reading NodeKey from %v: %v", filePath, err)
+		return nil, err
 	}
 	return nodeKey, nil
 }
 
-func genNodeKey(filePath string) (*NodeKey, error) {
-	privKey := ed25519.GenPrivKey()
-	nodeKey := &NodeKey{
-		PrivKey: privKey,
-	}
-
+// SaveAs persists the NodeKey to filePath.
+func (nodeKey *NodeKey) SaveAs(filePath string) error {
 	jsonBytes, err := cdc.MarshalJSON(nodeKey)
 	if err != nil {
-		return nil, err
+		return err
 	}
 	err = ioutil.WriteFile(filePath, jsonBytes, 0600)
 	if err != nil {
-		return nil, err
+		return err
 	}
-	return nodeKey, nil
+	return nil
 }
 
 //------------------------------------------------------------------------------

p2p/key_test.go

@@ -7,7 +7,9 @@ import (
 	"testing"
 
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 
+	"github.com/tendermint/tendermint/crypto/ed25519"
 	tmrand "github.com/tendermint/tendermint/libs/rand"
 )
 
@@ -23,6 +25,34 @@ func TestLoadOrGenNodeKey(t *testing.T) {
 	assert.Equal(t, nodeKey, nodeKey2)
 }
 
+func TestLoadNodeKey(t *testing.T) {
+	filePath := filepath.Join(os.TempDir(), tmrand.Str(12)+"_peer_id.json")
+
+	_, err := LoadNodeKey(filePath)
+	assert.True(t, os.IsNotExist(err))
+
+	_, err = LoadOrGenNodeKey(filePath)
+	require.NoError(t, err)
+
+	nodeKey, err := LoadNodeKey(filePath)
+	assert.NoError(t, err)
+	assert.NotNil(t, nodeKey)
+}
+
+func TestNodeKeySaveAs(t *testing.T) {
+	filePath := filepath.Join(os.TempDir(), tmrand.Str(12)+"_peer_id.json")
+
+	assert.NoFileExists(t, filePath)
+
+	privKey := ed25519.GenPrivKey()
+	nodeKey := &NodeKey{
+		PrivKey: privKey,
+	}
+	err := nodeKey.SaveAs(filePath)
+	assert.NoError(t, err)
+	assert.FileExists(t, filePath)
+}
+
 //----------------------------------------------------------
 
 func padBytes(bz []byte, targetBytes int) []byte {