Possible fix for #675 - Improve IOBase checks

docs/changes.rst

@@ -34,6 +34,12 @@ Unreleased.
    - :meth:`Image.region() <wand.image.BaseImage.region>`
    - :meth:`Image.splice() <wand.image.BaseImage.splice>`
 
+ - Fixed File I/O handling. [:issue:`675`]
+
+   - :meth:`Image.ping() <wand.image.Image.ping>`
+   - :meth:`Image.read() <wand.image.Image.read>`
+   - :meth:`Image.save() <wand.image.Image.save>`
+
  - [TEST] Added Python 3.12 regression test. [:issue:`648` by Thijs Triemstra]
 
 

wand/image.py

@@ -15,7 +15,7 @@
 import numbers
 import weakref
 from collections import abc
-from io import RawIOBase
+from io import IOBase
 
 from . import assertions
 from .api import libc, libmagick, library
@@ -9864,9 +9864,12 @@ def ping(cls, file=None, filename=None, blob=None, **kwargs):
         instance = cls()
         instance._preamble_read(**kwargs)
         if file is not None:
-            if (isinstance(file, RawIOBase) and
-                    hasattr(libc, 'fdopen') and hasattr(file, 'mode')):
-                fd = libc.fdopen(file.fileno(), file.mode)
+            is_fd = (isinstance(file, IOBase),
+                     hasattr(libc, 'fdopen'),
+                     callable(getattr(file, 'fileno', None)),
+                     hasattr(file, 'mode'))
+            if all(is_fd):
+                fd = libc.fdopen(file.fileno(), binary(file.mode))
                 r = library.MagickPingImageFile(instance.wand, fd)
             elif not callable(getattr(file, 'read', None)):
                 raise TypeError('file must be a readable file object'
@@ -10385,9 +10388,12 @@ def read(self, file=None, filename=None, blob=None, background=None,
             width=width
         )
         if file is not None:
-            if (isinstance(file, RawIOBase) and
-                    hasattr(libc, 'fdopen') and hasattr(file, 'mode')):
-                fd = libc.fdopen(file.fileno(), file.mode)
+            is_fd = (isinstance(file, IOBase),
+                     hasattr(libc, 'fdopen'),
+                     callable(getattr(file, 'fileno', None)),
+                     hasattr(file, 'mode'))
+            if all(is_fd):
+                fd = libc.fdopen(file.fileno(), binary(file.mode))
                 r = library.MagickReadImageFile(self.wand, fd)
             elif not callable(getattr(file, 'read', None)):
                 raise TypeError('file must be a readable file object'
@@ -10454,24 +10460,28 @@ def save(self, file=None, filename=None, adjoin=True):
         elif file is not None and filename is not None:
             raise TypeError('expected only one argument; but two passed')
         elif file is not None:
+            is_fd = (isinstance(file, IOBase),
+                     hasattr(libc, 'fdopen'),
+                     callable(getattr(file, 'fileno', None)),
+                     hasattr(file, 'mode'))
             if isinstance(file, str):
                 raise TypeError('file must be a writable file object, '
                                 'but {0!r} is a string; did you want '
                                 '.save(filename={0!r})?'.format(file))
-            elif isinstance(file, RawIOBase) and hasattr(libc, 'fdopen'):
-                fd = libc.fdopen(file.fileno(), file.mode)
+            elif all(is_fd):
+                fd = libc.fdopen(file.fileno(), binary(file.mode))
                 if library.MagickGetNumberImages(self.wand) > 1:
                     r = library.MagickWriteImagesFile(self.wand, fd)
                 else:
                     r = library.MagickWriteImageFile(self.wand, fd)
                 libc.fflush(fd)
                 if not r:
                     self.raise_exception()
+            elif not callable(getattr(file, 'write', None)):
+                raise TypeError('file must be a writable file object, '
+                                'but it does not have write() method: ' +
+                                repr(file))
             else:
-                if not callable(getattr(file, 'write', None)):
-                    raise TypeError('file must be a writable file object, '
-                                    'but it does not have write() method: ' +
-                                    repr(file))
                 file.write(self.make_blob())
         else:
             if not isinstance(filename, str):