Error returned if group flag needed for dkg but not set (#60)

* Error returned if group flag needed for dkg but not set

* Check that we have the right error

main.go

@@ -355,6 +355,12 @@ func runCmd(c *cli.Context) error {
 		slog.Print("Starting the dkg first.")
 		runDkg(c, drand, fs)
 	} else {
+		_, errG := fs.LoadGroup()
+		_, errS := fs.LoadShare()
+		_, errD := fs.LoadDistPublic()
+		if errG != nil || errS != nil || errD != nil {
+			slog.Fatalf("The DKG has not been run before, please provide a group file to do the setup.")
+		}
 		slog.Print("No group file given, drand will try to run as a beacon.")
 		drand, err = core.LoadDrand(fs, conf)
 		if err != nil {

main_test.go

@@ -8,6 +8,7 @@ import (
 	"os/exec"
 	"path"
 	"strconv"
+	"strings"
 	"testing"
 
 	"github.com/dedis/drand/core"
@@ -226,6 +227,22 @@ func TestResetBeacon(t *testing.T) {
 	/*}*/
 }
 
+// TestRunWhitoutGroupfileBeforeDKG tests the behavior of the run command whithout the flag --group-init
+// in a situation where the dkg was not ran before ()
+func TestRunWhitoutGroupfileBeforeDKG(t *testing.T) {
+	tmpPath := path.Join(os.TempDir(), "drand")
+	os.Mkdir(tmpPath, 0777)
+	defer os.RemoveAll(tmpPath)
+
+	//will try to run in beacon mode
+	cmd := exec.Command("drand", "-c", tmpPath, "run", "--insecure")
+	out, err := cmd.Output()
+	expectedErr := "The DKG has not been run before, please provide a group file to do the setup."
+	output := string(out)
+	require.Error(t, err)
+	require.True(t, strings.Contains(output, expectedErr))
+}
+
 func TestRunGroupInit(t *testing.T) {
 	tmpPath := path.Join(os.TempDir(), "drand")
 	os.Mkdir(tmpPath, 0777)