Use sys.getdefaultencoding() rather than assume 'utf-8'.

NEWS

@@ -79,6 +79,9 @@ New features
   variables were not set by default by rpy2 and this could lead to issues (see issue #1033).
   The variables are now added to `os.environ`.
 
+- On systems where the default encoding is not utf-8, converting
+  R strings to Python can result in decoding errors (issue #1018).
+
 Bugs fixed
 ----------
 

rpy2/rinterface.py

@@ -11,6 +11,7 @@
 import platform
 import signal
 import subprocess
+import sys
 import textwrap
 import threading
 import typing
@@ -293,7 +294,7 @@ def __str__(self) -> str:
         return conversion._cchar_to_str(
             openrlib._STRING_VALUE(
                 self._sexpobject._cdata
-            ), 'utf-8'
+            ), sys.getdefaultencoding()
         )
 
 

rpy2/rinterface_lib/callbacks.py

@@ -6,6 +6,7 @@
 
 from contextlib import contextmanager
 import logging
+import sys
 import typing
 import os
 from rpy2.rinterface_lib import openrlib
@@ -14,7 +15,7 @@
 
 logger = logging.getLogger(__name__)
 
-_CCHAR_ENCODING = 'utf-8'
+_CCHAR_ENCODING = sys.getdefaultencoding()
 
 
 # TODO: rename to "replace_in_module"

rpy2/rinterface_lib/conversion.py

@@ -3,6 +3,7 @@
 # TODO: rename the module with a prefix _ to indicate that this should
 #   not be used outside of rpy2's own code
 
+import sys
 from typing import Callable
 from typing import Dict
 from typing import Optional
@@ -118,7 +119,8 @@ def _complex_to_sexp(val: complex):
 #   CE_ANY    = 99
 
 # Default encoding for converting R strings to Python
-_R_ENC_PY = {None: 'ascii'}
+_R_ENC_PY = {None: 'ascii',
+             'native.enc': sys.getdefaultencoding()}
 
 
 def _str_to_cchar(s: str, encoding: str = 'utf-8'):