fix: use descriptive error for unknown block options in health and log plugins (#8128)

plugin/log/setup.go

@@ -86,7 +86,7 @@ func logParse(c *caddy.Controller) ([]Rule, error) {
 					classes[cls] = struct{}{}
 				}
 			default:
-				return nil, c.ArgErr()
+				return nil, c.Errf("unknown property '%s'", c.Val())
 			}
 		}
 		if len(classes) == 0 {

plugin/log/setup_test.go

@@ -2,6 +2,7 @@ package log
 
 import (
 	"reflect"
+	"strings"
 	"testing"
 
 	"github.com/coredns/caddy"
@@ -182,3 +183,14 @@ func TestLogParse(t *testing.T) {
 		}
 	}
 }
+
+func TestLogParseUnknownProperty(t *testing.T) {
+	c := caddy.NewTestController("dns", `log { unknown }`)
+	_, err := logParse(c)
+	if err == nil {
+		t.Fatal("expected error for unknown block option, got nil")
+	}
+	if !strings.Contains(err.Error(), "unknown property") {
+		t.Errorf("expected error to contain 'unknown property', got: %v", err)
+	}
+}