Added a function to allow ignoring top-level unknown config option

This will be required for NATS Streaming server since streaming
allows user to have NATS and Streaming specific options in same
file.

Signed-off-by: Ivan Kozlovic <ivan@synadia.com>

server/opts.go

@@ -27,6 +27,7 @@ import (
 	"regexp"
 	"strconv"
 	"strings"
+	"sync/atomic"
 	"time"
 
 	"github.com/nats-io/jwt"
@@ -34,6 +35,19 @@ import (
 	"github.com/nats-io/nkeys"
 )
 
+var allowUnknownTopLevelField = int32(0)
+
+// AllowUnknownTopLevelConfigurationField sets if the processing of a
+// configuration file returns an error if it finds an unknown top-level
+// configuration option.
+func AllowUnknownTopLevelConfigurationField(allow bool) {
+	var val int32
+	if allow {
+		val = int32(1)
+	}
+	atomic.StoreInt32(&allowUnknownTopLevelField, val)
+}
+
 // ClusterOpts are options for clusters.
 // NOTE: This structure is no longer used for monitoring endpoints
 // and json tags are deprecated and may be removed in the future.
@@ -693,7 +707,7 @@ func (o *Options) ProcessConfigFile(configFile string) error {
 		case "reconnect_error_reports":
 			o.ReconnectErrorReports = int(v.(int64))
 		default:
-			if !tk.IsUsedVariable() {
+			if au := atomic.LoadInt32(&allowUnknownTopLevelField); au == 0 && !tk.IsUsedVariable() {
 				err := &unknownConfigFieldErr{
 					field: k,
 					configErr: configErr{

server/opts_test.go

@@ -1819,3 +1819,44 @@ func TestLargeMaxPayload(t *testing.T) {
 		t.Fatalf("Expected an error from too large of a max_payload entry")
 	}
 }
+
+func TestHandleUnknownTopLevelConfigurationField(t *testing.T) {
+	conf := createConfFile(t, []byte(`
+		port: 1234
+		streaming {
+			id: "me"
+		}
+	`))
+	defer os.Remove(conf)
+
+	// Verify that we get an error because of unknown "streaming" field.
+	opts := &Options{}
+	if err := opts.ProcessConfigFile(conf); err == nil || !strings.Contains(err.Error(), "streaming") {
+		t.Fatal("Expected error, got none")
+	}
+
+	// Verify that if that is set, we get no error
+	AllowUnknownTopLevelConfigurationField(true)
+	defer AllowUnknownTopLevelConfigurationField(false)
+
+	if err := opts.ProcessConfigFile(conf); err != nil {
+		t.Fatalf("Unexpected error: %v", err)
+	}
+	if opts.Port != 1234 {
+		t.Fatalf("Port was not parsed correctly: %v", opts.Port)
+	}
+
+	// Verify that ignore works only on top level fields.
+	changeCurrentConfigContentWithNewContent(t, conf, []byte(`
+		port: 1234
+		cluster {
+			non_top_level_unknown_field: 123
+		}
+		streaming {
+			id: "me"
+		}
+	`))
+	if err := opts.ProcessConfigFile(conf); err == nil || !strings.Contains(err.Error(), "non_top_level") {
+		t.Fatal("Expected error, got none")
+	}
+}