Simplify LockTarget.IsEmpty implementation (#32607)

api/types/lock.go

@@ -218,11 +218,6 @@ func (c *LockV2) CheckAndSetDefaults() error {
 	return nil
 }
 
-// IsEmpty returns true if none of the target's fields is set.
-func (t LockTarget) IsEmpty() bool {
-	return protoKnownFieldsEqual(&t, &LockTarget{})
-}
-
 // IntoMap returns the target attributes in the form of a map.
 func (t LockTarget) IntoMap() (map[string]string, error) {
 	m := map[string]string{}
@@ -237,6 +232,19 @@ func (t *LockTarget) FromMap(m map[string]string) error {
 	return trace.Wrap(utils.ObjectToStruct(m, t))
 }
 
+// IsEmpty returns true if none of the target's fields is set.
+func (t LockTarget) IsEmpty() bool {
+	return t.User == "" &&
+		t.Role == "" &&
+		t.Login == "" &&
+		t.Node == "" &&
+		t.MFADevice == "" &&
+		t.WindowsDesktop == "" &&
+		t.AccessRequest == "" &&
+		t.Device == "" &&
+		t.ServerID == ""
+}
+
 // Match returns true if the lock's target is matched by this target.
 func (t LockTarget) Match(lock Lock) bool {
 	if t.IsEmpty() {

api/types/lock_test.go

@@ -17,6 +17,8 @@ limitations under the License.
 package types
 
 import (
+	"reflect"
+	"strings"
 	"testing"
 
 	"github.com/google/go-cmp/cmp"
@@ -112,3 +114,22 @@ func TestLockTargetMatch(t *testing.T) {
 	// Test that a lock with ServerID field set matches any target with ServerID.
 	require.True(t, targetServerID.Match(lockServerID))
 }
+
+// TestLockTargetIsEmpty checks that the implementation of [LockTarget.IsEmpty]
+// is correct by filling one field at a time and expecting IsEmpty to return
+// false. Only the public fields that don't start with `XXX_` are checked (as
+// those are gogoproto-internal fields).
+func TestLockTargetIsEmpty(t *testing.T) {
+	require.True(t, (LockTarget{}).IsEmpty())
+
+	for i, field := range reflect.VisibleFields(reflect.TypeOf(LockTarget{})) {
+		if strings.HasPrefix(field.Name, "XXX_") {
+			continue
+		}
+
+		var lt LockTarget
+		// if we add non-string fields to LockTarget we need a type switch here
+		reflect.ValueOf(&lt).Elem().Field(i).SetString("nonempty")
+		require.False(t, lt.IsEmpty(), "field name: %v", field.Name)
+	}
+}