[#1969] local_object_storage: Add a type for logical errors

All logic errors are wrapped in `logicerr.Logical` type and do not
affect shard error counter.

Signed-off-by: Evgenii Stratonikov <evgeniy@morphbits.ru>

pkg/local_object_storage/util/logicerr/error.go

@@ -0,0 +1,21 @@
+package logicerr
+
+// Logical is a wrapper for logical errors.
+type Logical struct {
+	err error
+}
+
+// Error implements the error interface.
+func (e Logical) Error() string {
+	return e.err.Error()
+}
+
+// Wrap wraps arbitrary error into a logical one.
+func Wrap(err error) Logical {
+	return Logical{err: err}
+}
+
+// Unwrap returns underlying error.
+func (e Logical) Unwrap() error {
+	return e.err
+}

pkg/local_object_storage/util/logicerr/error_test.go

@@ -0,0 +1,58 @@
+package logicerr
+
+import (
+	"errors"
+	"fmt"
+	"strconv"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestError(t *testing.T) {
+	t.Run("errors.Is", func(t *testing.T) {
+		e1 := errors.New("some error")
+		ee := Wrap(e1)
+		require.ErrorIs(t, ee, e1)
+
+		e2 := fmt.Errorf("wrap: %w", e1)
+		ee = Wrap(e2)
+		require.ErrorIs(t, ee, e1)
+		require.ErrorIs(t, ee, e2)
+
+		require.Equal(t, errors.Unwrap(ee), e2)
+	})
+
+	t.Run("errors.As", func(t *testing.T) {
+		e1 := testError{42}
+		ee := Wrap(e1)
+
+		{
+			var actual testError
+			require.ErrorAs(t, ee, &actual)
+			require.Equal(t, e1.data, actual.data)
+		}
+		{
+			var actual Logical
+			require.ErrorAs(t, ee, &actual)
+			require.Equal(t, e1, actual.err)
+		}
+
+		e2 := fmt.Errorf("wrap: %w", e1)
+		ee = Wrap(e2)
+
+		{
+			var actual testError
+			require.ErrorAs(t, ee, &actual)
+			require.Equal(t, e1.data, actual.data)
+		}
+	})
+}
+
+type testError struct {
+	data uint64
+}
+
+func (e testError) Error() string {
+	return strconv.FormatUint(e.data, 10)
+}