BUG: Fix pprint failure on non-string __qualname__ or __name__.

Fixes a bug where pprint would fail to correctly render a class whose
__qualname__ is not a string, or a class that doesn't have a
__qualname__ and whose __name__ is not a string.

IPython/lib/pretty.py

@@ -85,7 +85,7 b' import re'
 import datetime
 from collections import deque
 
-from IPython.utils.py3compat import PY3, cast_unicode
+from IPython.utils.py3compat import PY3, cast_unicode, string_types
 from IPython.utils.encoding import get_stream_enc
 
 from io import StringIO
@@ -671,7 +671,16 b' def _type_pprint(obj, p, cycle):'
         return
 
     mod = _safe_getattr(obj, '__module__', None)
-    name = _safe_getattr(obj, '__qualname__', obj.__name__)
+    try:
+        name = obj.__qualname__
+        if not isinstance(name, string_types):
+            # This can happen if the type implements __qualname__ as a property
+            # or other descriptor in Python 2.
+            raise Exception("Try __name__")
+    except Exception:
+        name = obj.__name__
+        if not isinstance(name, string_types):
+            name = '<unknown type>'
 
     if mod in (None, '__builtin__', 'builtins', 'exceptions'):
         p.text(name)

IPython/lib/tests/test_pretty.py

@@ -11,7 +11,7 b' from collections import Counter, defaultdict, deque, OrderedDict'
 import nose.tools as nt
 
 from IPython.lib import pretty
-from IPython.testing.decorators import skip_without
+from IPython.testing.decorators import skip_without, py2_only
 from IPython.utils.py3compat import PY3, unicode_to_str
 
 if PY3:
@@ -272,6 +272,83 b' def test_basic_class():'
     nt.assert_true(type_pprint_wrapper.called)
 
 
+# This is only run on Python 2 because in Python 3 the language prevents you
+# from setting a non-unicode value for __qualname__ on a metaclass, and it
+# doesn't respect the descriptor protocol if you subclass unicode and implement
+# __get__.
+@py2_only
+def test_fallback_to__name__on_type():
+    # Test that we correctly repr types that have non-string values for
+    # __qualname__ by falling back to __name__
+
+    class Type(object):
+        __qualname__ = 5
+
+    # Test repring of the type.
+    stream = StringIO()
+    printer = pretty.RepresentationPrinter(stream)
+
+    printer.pretty(Type)
+    printer.flush()
+    output = stream.getvalue()
+
+    # If __qualname__ is malformed, we should fall back to __name__.
+    expected = '.'.join([__name__, Type.__name__])
+    nt.assert_equal(output, expected)
+
+    # Clear stream buffer.
+    stream.buf = ''
+
+    # Test repring of an instance of the type.
+    instance = Type()
+    printer.pretty(instance)
+    printer.flush()
+    output = stream.getvalue()
+
+    # Should look like:
+    # <IPython.lib.tests.test_pretty.Type at 0x7f7658ae07d0>
+    prefix = '<' + '.'.join([__name__, Type.__name__]) + ' at 0x'
+    nt.assert_true(output.startswith(prefix))
+
+
+@py2_only
+def test_fail_gracefully_on_bogus__qualname__and__name__():
+    # Test that we correctly repr types that have non-string values for both
+    # __qualname__ and __name__
+
+    class Meta(type):
+        __name__ = 5
+
+    class Type(object):
+        __metaclass__ = Meta
+        __qualname__ = 5
+
+    stream = StringIO()
+    printer = pretty.RepresentationPrinter(stream)
+
+    printer.pretty(Type)
+    printer.flush()
+    output = stream.getvalue()
+
+    # If we can't find __name__ or __qualname__ just use a sentinel string.
+    expected = '.'.join([__name__, '<unknown type>'])
+    nt.assert_equal(output, expected)
+
+    # Clear stream buffer.
+    stream.buf = ''
+
+    # Test repring of an instance of the type.
+    instance = Type()
+    printer.pretty(instance)
+    printer.flush()
+    output = stream.getvalue()
+
+    # Should look like:
+    # <IPython.lib.tests.test_pretty.<unknown type> at 0x7f7658ae07d0>
+    prefix = '<' + '.'.join([__name__, '<unknown type>']) + ' at 0x'
+    nt.assert_true(output.startswith(prefix))
+
+
 def test_collections_defaultdict():
     # Create defaultdicts with cycles
     a = defaultdict()

IPython/testing/decorators.py

@@ -48,7 +48,7 b' from .ipunittest import ipdoctest, ipdocstring'
 from IPython.external.decorators import *
 
 # For onlyif_cmd_exists decorator
-from IPython.utils.py3compat import string_types, which
+from IPython.utils.py3compat import string_types, which, PY2, PY3
 
 #-----------------------------------------------------------------------------
 # Classes and functions
@@ -336,6 +336,9 b" skip_known_failure = knownfailureif(True,'This test is known to fail')"
 known_failure_py3 = knownfailureif(sys.version_info[0] >= 3, 
                                     'This test is known to fail on Python 3.')
 
+py2_only = skipif(PY3, "This test only runs on Python 2.")
+py3_only = skipif(PY2, "This test only runs on Python 3.")
+
 # A null 'decorator', useful to make more readable code that needs to pick
 # between different decorators based on OS or other conditions
 null_deco = lambda f: f

IPython/utils/py3compat.py

@@ -289,6 +289,9 b' else:'
                 exec(compiler(scripttext, filename, 'exec'), glob, loc)
 
 
+PY2 = not PY3
+
+
 def annotate(**kwargs):
     """Python 3 compatible function annotation for Python 2."""
     if not kwargs: