BUG: fix check_folder to not raise exception for mem. streams

src/xtgeo/grid3d/_gridprop_export.py

@@ -47,8 +47,7 @@ def to_file(
         name = gridprop.name or ""
 
     xtg_file = FileWrapper(pfile, mode="rb")
-    if not xtg_file.memstream:
-        xtg_file.check_folder(raiseerror=OSError)
+    xtg_file.check_folder(raiseerror=OSError)
 
     if fformat in FileFormat.ROFF_BINARY.value + FileFormat.ROFF_ASCII.value:
         _export_roff(gridprop, xtg_file.name, name, binary, append=append)

src/xtgeo/grid3d/grid.py

@@ -711,8 +711,7 @@ def to_file(self, gfile: FileLike, fformat: str = "roff") -> None:
         """
         _gfile = FileWrapper(gfile, mode="wb")
 
-        if not _gfile.memstream:
-            _gfile.check_folder(raiseerror=OSError)
+        _gfile.check_folder(raiseerror=OSError)
 
         if fformat in FileFormat.ROFF_BINARY.value:
             _grid_export.export_roff(self, _gfile.name, "binary")

src/xtgeo/io/_file.py

@@ -301,12 +301,14 @@ def check_folder(
             ValueError: If the file is a memstream
 
         """
-        # Redundant but mypy can't follow when memstream is True
-        if self.memstream or isinstance(self.file, (io.BytesIO, io.StringIO)):
-            raise ValueError("Cannot check folder status of an in-memory file")
-
         logger.debug("Checking folder...")
 
+        if self.memstream or isinstance(self.file, (io.BytesIO, io.StringIO)):
+            logger.info(
+                "Cannot check folder status of an in-memory file, just return True"
+            )
+            return True
+
         folder = self.file.parent
         if raisetext is None:
             raisetext = f"Folder {folder.name} does not exist or cannot be accessed"

src/xtgeo/surface/regular_surface.py

@@ -994,10 +994,9 @@ def to_file(
             warnings.warn(msg, UserWarning)
 
         mfile = FileWrapper(mfile, mode="wb", obj=self)
+        mfile.check_folder(raiseerror=OSError)
 
-        if not mfile.memstream:
-            mfile.check_folder(raiseerror=OSError)
-        else:
+        if mfile.memstream:
             engine = "python"
 
         if fformat in FileFormat.IRAP_ASCII.value:
@@ -1076,8 +1075,7 @@ def to_hdf(
         # developing, in prep and experimental!
         mfile = FileWrapper(mfile, mode="wb", obj=self)
 
-        if not mfile.memstream:
-            mfile.check_folder(raiseerror=OSError)
+        mfile.check_folder(raiseerror=OSError)
 
         _regsurf_export.export_hdf5_regsurf(self, mfile, compression=compression)
         return mfile.file