config: parsed empty config only show warnings

Signed-off-by: Waldemar Quevedo <wally@nats.io>

server/config_check_test.go

@@ -1579,6 +1579,23 @@ func TestConfigCheck(t *testing.T) {
 			errorLine: 5,
 			errorPos:  6,
 		},
+		{
+			name:       "show warnings on empty configs without values",
+			config:     ``,
+			warningErr: errors.New(`config has no values or is empty`),
+			errorLine:  0,
+			errorPos:   0,
+			reason:     "",
+		},
+		{
+			name: "show warnings on empty configs without values and only comments",
+			config: `# Valid file but has no usable values.
+                                    `,
+			warningErr: errors.New(`config has no values or is empty`),
+			errorLine:  0,
+			errorPos:   0,
+			reason:     "",
+		},
 	}
 
 	checkConfig := func(config string) error {
@@ -1620,6 +1637,8 @@ func TestConfigCheck(t *testing.T) {
 					if test.reason != "" {
 						msg += ": " + test.reason
 					}
+				} else if test.warningErr != nil {
+					msg = expectedErr.Error()
 				} else {
 					msg = test.reason
 				}

server/opts.go

@@ -744,6 +744,9 @@ func (o *Options) ProcessConfigFile(configFile string) error {
 	// Collect all errors and warnings and report them all together.
 	errors := make([]error, 0)
 	warnings := make([]error, 0)
+	if len(m) == 0 {
+		warnings = append(warnings, fmt.Errorf("%s: config has no values or is empty", configFile))
+	}
 
 	// First check whether a system account has been defined,
 	// as that is a condition for other features to be enabled.