Add error check and improve msg

The patchset checks the error when doing yaml marshal, and improves
the message when error happens.

Change-Id: I40fb7dbe930bcdc6563078daab50f4f4564c3381
Signed-off-by: Baohua Yang <yangbaohua@gmail.com>
Signed-off-by: Baohua Yang <baohua.yang@oracle.com>

cmd/common/config.go

@@ -42,24 +42,28 @@ func (c Config) ToFile(file string) error {
 	if err := validateConfig(c); err != nil {
 		return errors.Wrap(err, "config isn't valid")
 	}
-	b, _ := yaml.Marshal(c)
+	b, err := yaml.Marshal(c)
+	if err != nil {
+		return errors.Wrap(err, "failed to marshal config")
+	}
 	if err := os.WriteFile(file, b, 0o600); err != nil {
 		return errors.Errorf("failed writing file %s: %v", file, err)
 	}
 	return nil
 }
 
 func validateConfig(conf Config) error {
-	nonEmptyStrings := []string{
-		conf.SignerConfig.MSPID,
-		conf.SignerConfig.IdentityPath,
-		conf.SignerConfig.KeyPath,
+	nonEmptyElems := map[string]string{
+		"MSPID":        conf.SignerConfig.MSPID,
+		"IdentityPath": conf.SignerConfig.IdentityPath,
+		"KeyPath":      conf.SignerConfig.KeyPath,
 	}
 
-	for _, s := range nonEmptyStrings {
-		if s == "" {
-			return errors.New("empty string that is mandatory")
+	for key, value := range nonEmptyElems {
+		if value == "" {
+			return errors.Errorf("%s is mandatory and cannot be empty", key)
 		}
 	}
+
 	return nil
 }

cmd/discover/main_test.go

@@ -27,5 +27,5 @@ func TestMissingArguments(t *testing.T) {
 	process, err := Start(cmd, nil, nil)
 	gt.Expect(err).NotTo(HaveOccurred())
 	gt.Eventually(process, 5*time.Second).Should(Exit(1))
-	gt.Expect(process.Err).To(gbytes.Say("empty string that is mandatory"))
+	gt.Expect(process.Err).To(gbytes.Say("IdentityPath|KeyPath is mandatory and cannot be empty"))
 }