catch a fringe case where we parse in a core.ip, but also an empty co…

…nfig with no defaults (likely never happen)

nodebuilder/core/flags.go

@@ -50,11 +50,14 @@ func ParseFlags(
 		return nil
 	}
 
-	if cmd.Flag(coreRPCFlag).Changed {
+	// in the case that the RPC port is not set, use the default port
+	// or in the case a value has been set via flag,
+	// set that as highest precedence
+	if cfg.RPCPort == "" || cmd.Flag(coreRPCFlag).Changed {
 		rpc := cmd.Flag(coreRPCFlag).Value.String()
 		cfg.RPCPort = rpc
 	}
-	if cmd.Flag(coreGRPCFlag).Changed {
+	if cfg.GRPCPort == "" || cmd.Flag(coreGRPCFlag).Changed {
 		grpc := cmd.Flag(coreGRPCFlag).Value.String()
 		cfg.GRPCPort = grpc
 	}

nodebuilder/core/flags_test.go

@@ -40,6 +40,17 @@ func TestParseFlags(t *testing.T) {
 			},
 			expectError: false,
 		},
+		{
+			name:     "only core.ip, empty port values",
+			args:     []string{"--core.ip=127.0.0.1"},
+			inputCfg: Config{},
+			expectedCfg: Config{
+				IP:       "127.0.0.1",
+				RPCPort:  DefaultRPCPort,
+				GRPCPort: DefaultGRPCPort,
+			},
+			expectError: false,
+		},
 		{
 			name: "no flags, values from input config.toml ",
 			args: []string{},