Return nil block number on Grandpa pause/resume not found

dot/digest/digest_test.go

@@ -176,6 +176,7 @@ func TestHandler_GrandpaPauseAndResume(t *testing.T) {
 	require.NoError(t, err)
 	nextPause, err := handler.grandpaState.(*state.GrandpaState).GetNextPause()
 	require.NoError(t, err)
+	require.NotNil(t, nextPause) // ensure pause was found
 	require.Equal(t, big.NewInt(int64(p.Delay)), nextPause)
 
 	headers, _ := state.AddBlocksToState(t, handler.blockState.(*state.BlockState), 3, false)
@@ -211,6 +212,7 @@ func TestHandler_GrandpaPauseAndResume(t *testing.T) {
 
 	nextResume, err := handler.grandpaState.(*state.GrandpaState).GetNextResume()
 	require.NoError(t, err)
+	require.NotNil(t, nextResume) // ensure resume was found
 	require.Equal(t, big.NewInt(int64(r.Delay)+int64(p.Delay)), nextResume)
 }
 

dot/state/grandpa.go

@@ -234,11 +234,14 @@ func (s *GrandpaState) SetNextPause(number *big.Int) error {
 }
 
 // GetNextPause returns the block number of the next grandpa pause.
-// It returns an error on failure, which is contains the
-// chaindb.ErrKeyNotFound error if the key is not found.
+// If the key is not found in the database, a nil block number is returned
+// to indicate there is no upcoming Grandpa pause.
+// It returns an error on failure.
 func (s *GrandpaState) GetNextPause() (*big.Int, error) {
 	num, err := s.db.Get(pauseKey)
-	if err != nil {
+	if errors.Is(err, chaindb.ErrKeyNotFound) {
+		return nil, nil //nolint:nilnil
+	} else if err != nil {
 		return nil, err
 	}
 
@@ -251,11 +254,14 @@ func (s *GrandpaState) SetNextResume(number *big.Int) error {
 }
 
 // GetNextResume returns the block number of the next grandpa resume.
-// It returns an error on failure, which is contains the
-// chaindb.ErrKeyNotFound error if the key is not found.
+// If the key is not found in the database, a nil block number is returned
+// to indicate there is no upcoming Grandpa resume.
+// It returns an error on failure.
 func (s *GrandpaState) GetNextResume() (*big.Int, error) {
 	num, err := s.db.Get(resumeKey)
-	if err != nil {
+	if errors.Is(err, chaindb.ErrKeyNotFound) {
+		return nil, nil //nolint:nilnil
+	} else if err != nil {
 		return nil, err
 	}