IOStream: Ignore missing attrs from `dir()`. #6386

In some cases calling `getattr()` on attributes found with
`dir()` will fail. This is seen in Issue  #6386.

The attribute in that issue is `name`, which is not needed for
`IOStream` to work correctly. This fix will set the attribute
to `None` and move on.

Tests were added in `IPython.utils.tests.test_io.py` to catch
any regressions.

IPython/utils/io.py

@@ -1,240 +1,245 b''
 # encoding: utf-8
 """
 IO related utilities.
 """
 
 # Copyright (c) IPython Development Team.
 # Distributed under the terms of the Modified BSD License.
 
 
 
 import atexit
 import os
 import sys
 import tempfile
 import warnings
 from warnings import warn
 
 from IPython.utils.decorators import undoc
 from .capture import CapturedIO, capture_output
 from .py3compat import input
 
 @undoc
 class IOStream:
 
     def __init__(self, stream, fallback=None):
         warn('IOStream is deprecated since IPython 5.0, use sys.{stdin,stdout,stderr} instead',
              DeprecationWarning, stacklevel=2)
         if not hasattr(stream,'write') or not hasattr(stream,'flush'):
             if fallback is not None:
                 stream = fallback
             else:
                 raise ValueError("fallback required, but not specified")
         self.stream = stream
         self._swrite = stream.write
 
         # clone all methods not overridden:
         def clone(meth):
             return not hasattr(self, meth) and not meth.startswith('_')
         for meth in filter(clone, dir(stream)):
-            setattr(self, meth, getattr(stream, meth))
+            try:
+                val = getattr(stream, meth)
+            except AttributeError:
+                pass
+            else:
+                setattr(self, meth, val)
 
     def __repr__(self):
         cls = self.__class__
         tpl = '{mod}.{cls}({args})'
         return tpl.format(mod=cls.__module__, cls=cls.__name__, args=self.stream)
 
     def write(self,data):
         warn('IOStream is deprecated since IPython 5.0, use sys.{stdin,stdout,stderr} instead',
              DeprecationWarning, stacklevel=2)
         try:
             self._swrite(data)
         except:
             try:
                 # print handles some unicode issues which may trip a plain
                 # write() call.  Emulate write() by using an empty end
                 # argument.
                 print(data, end='', file=self.stream)
             except:
                 # if we get here, something is seriously broken.
                 print('ERROR - failed to write data to stream:', self.stream,
                       file=sys.stderr)
 
     def writelines(self, lines):
         warn('IOStream is deprecated since IPython 5.0, use sys.{stdin,stdout,stderr} instead',
              DeprecationWarning, stacklevel=2)
         if isinstance(lines, str):
             lines = [lines]
         for line in lines:
             self.write(line)
 
     # This class used to have a writeln method, but regular files and streams
     # in Python don't have this method. We need to keep this completely
     # compatible so we removed it.
 
     @property
     def closed(self):
         return self.stream.closed
 
     def close(self):
         pass
 
 # setup stdin/stdout/stderr to sys.stdin/sys.stdout/sys.stderr
 devnull = open(os.devnull, 'w')
 atexit.register(devnull.close)
 
 # io.std* are deprecated, but don't show our own deprecation warnings
 # during initialization of the deprecated API.
 with warnings.catch_warnings():
     warnings.simplefilter('ignore', DeprecationWarning)
     stdin = IOStream(sys.stdin, fallback=devnull)
     stdout = IOStream(sys.stdout, fallback=devnull)
     stderr = IOStream(sys.stderr, fallback=devnull)
 
 class Tee(object):
     """A class to duplicate an output stream to stdout/err.
 
     This works in a manner very similar to the Unix 'tee' command.
 
     When the object is closed or deleted, it closes the original file given to
     it for duplication.
     """
     # Inspired by:
     # http://mail.python.org/pipermail/python-list/2007-May/442737.html
 
     def __init__(self, file_or_name, mode="w", channel='stdout'):
         """Construct a new Tee object.
 
         Parameters
         ----------
         file_or_name : filename or open filehandle (writable)
           File that will be duplicated
 
         mode : optional, valid mode for open().
           If a filename was give, open with this mode.
 
         channel : str, one of ['stdout', 'stderr']
         """
         if channel not in ['stdout', 'stderr']:
             raise ValueError('Invalid channel spec %s' % channel)
 
         if hasattr(file_or_name, 'write') and hasattr(file_or_name, 'seek'):
             self.file = file_or_name
         else:
             self.file = open(file_or_name, mode)
         self.channel = channel
         self.ostream = getattr(sys, channel)
         setattr(sys, channel, self)
         self._closed = False
 
     def close(self):
         """Close the file and restore the channel."""
         self.flush()
         setattr(sys, self.channel, self.ostream)
         self.file.close()
         self._closed = True
 
     def write(self, data):
         """Write data to both channels."""
         self.file.write(data)
         self.ostream.write(data)
         self.ostream.flush()
 
     def flush(self):
         """Flush both channels."""
         self.file.flush()
         self.ostream.flush()
 
     def __del__(self):
         if not self._closed:
             self.close()
 
 
 def ask_yes_no(prompt, default=None, interrupt=None):
     """Asks a question and returns a boolean (y/n) answer.
 
     If default is given (one of 'y','n'), it is used if the user input is
     empty. If interrupt is given (one of 'y','n'), it is used if the user
     presses Ctrl-C. Otherwise the question is repeated until an answer is
     given.
 
     An EOF is treated as the default answer.  If there is no default, an
     exception is raised to prevent infinite loops.
 
     Valid answers are: y/yes/n/no (match is not case sensitive)."""
 
     answers = {'y':True,'n':False,'yes':True,'no':False}
     ans = None
     while ans not in answers.keys():
         try:
             ans = input(prompt+' ').lower()
             if not ans:  # response was an empty string
                 ans = default
         except KeyboardInterrupt:
             if interrupt:
                 ans = interrupt
             print("\r")
         except EOFError:
             if default in answers.keys():
                 ans = default
                 print()
             else:
                 raise
 
     return answers[ans]
 
 
 def temp_pyfile(src, ext='.py'):
     """Make a temporary python file, return filename and filehandle.
 
     Parameters
     ----------
     src : string or list of strings (no need for ending newlines if list)
       Source code to be written to the file.
 
     ext : optional, string
       Extension for the generated file.
 
     Returns
     -------
     (filename, open filehandle)
       It is the caller's responsibility to close the open file and unlink it.
     """
     fname = tempfile.mkstemp(ext)[1]
     f = open(fname,'w')
     f.write(src)
     f.flush()
     return fname, f
 
 def atomic_writing(*args, **kwargs):
     """DEPRECATED: moved to notebook.services.contents.fileio"""
     warn("IPython.utils.io.atomic_writing has moved to notebook.services.contents.fileio", stacklevel=2)
     from notebook.services.contents.fileio import atomic_writing
     return atomic_writing(*args, **kwargs)
 
 def raw_print(*args, **kw):
     """Raw print to sys.__stdout__, otherwise identical interface to print()."""
 
     print(*args, sep=kw.get('sep', ' '), end=kw.get('end', '\n'),
           file=sys.__stdout__)
     sys.__stdout__.flush()
 
 
 def raw_print_err(*args, **kw):
     """Raw print to sys.__stderr__, otherwise identical interface to print()."""
 
     print(*args, sep=kw.get('sep', ' '), end=kw.get('end', '\n'),
           file=sys.__stderr__)
     sys.__stderr__.flush()
 
 
 # Short aliases for quick debugging, do NOT use these in production code.
 rprint = raw_print
 rprinte = raw_print_err
 
 
 def unicode_std_stream(stream='stdout'):
     """DEPRECATED, moved to nbconvert.utils.io"""
     warn("IPython.utils.io.unicode_std_stream has moved to nbconvert.utils.io", stacklevel=2)
     from nbconvert.utils.io import unicode_std_stream
     return unicode_std_stream(stream)

IPython/utils/tests/test_io.py

@@ -1,81 +1,94 b''
 # encoding: utf-8
 """Tests for io.py"""
 
 # Copyright (c) IPython Development Team.
 # Distributed under the terms of the Modified BSD License.
 
 
 import io as stdlib_io
 import os.path
 import stat
 import sys
 from io import StringIO
 
 from subprocess import Popen, PIPE
 import unittest
 
 import nose.tools as nt
 
 from IPython.testing.decorators import skipif, skip_win32
-from IPython.utils.io import Tee, capture_output
+from IPython.utils.io import IOStream, Tee, capture_output
 from IPython.utils.py3compat import doctest_refactor_print
 from IPython.utils.tempdir import TemporaryDirectory
 
 
 def test_tee_simple():
     "Very simple check with stdout only"
     chan = StringIO()
     text = 'Hello'
     tee = Tee(chan, channel='stdout')
     print(text, file=chan)
     nt.assert_equal(chan.getvalue(), text+"\n")
 
 
 class TeeTestCase(unittest.TestCase):
 
     def tchan(self, channel, check='close'):
         trap = StringIO()
         chan = StringIO()
         text = 'Hello'
         
         std_ori = getattr(sys, channel)
         setattr(sys, channel, trap)
 
         tee = Tee(chan, channel=channel)
         print(text, end='', file=chan)
         setattr(sys, channel, std_ori)
         trap_val = trap.getvalue()
         nt.assert_equal(chan.getvalue(), text)
         if check=='close':
             tee.close()
         else:
             del tee
 
     def test(self):
         for chan in ['stdout', 'stderr']:
             for check in ['close', 'del']:
                 self.tchan(chan, check)
 
 def test_io_init():
     """Test that io.stdin/out/err exist at startup"""
     for name in ('stdin', 'stdout', 'stderr'):
         cmd = doctest_refactor_print("from IPython.utils import io;print io.%s.__class__"%name)
         p = Popen([sys.executable, '-c', cmd],
                     stdout=PIPE)
         p.wait()
         classname = p.stdout.read().strip().decode('ascii')
         # __class__ is a reference to the class object in Python 3, so we can't
         # just test for string equality.
         assert 'IPython.utils.io.IOStream' in classname, classname
 
+def test_IOStream_init():
+    """IOStream initializes from a file-like object missing attributes. """
+    # Cause a failure from getattr and dir(). (Issue #6386)
+    class BadStringIO(StringIO):
+        def __dir__(self):
+            attrs = super(StringIO, self).__dir__()
+            attrs.append('name')
+            return attrs
+
+    iostream = IOStream(BadStringIO())
+    iostream.write('hi, bad iostream\n')
+    assert not hasattr(iostream, 'name')
+
 def test_capture_output():
     """capture_output() context works"""
     
     with capture_output() as io:
         print('hi, stdout')
         print('hi, stderr', file=sys.stderr)
     
     nt.assert_equal(io.stdout, 'hi, stdout\n')
     nt.assert_equal(io.stderr, 'hi, stderr\n')