Fix problems with side effects and python 2.6.

The isolation decorator wasn't working correctly (side effects were leaking
into other tests by breaking the user namespace).  Rewrote it to instead use a
simpler but more robust strategy (that is also faster).  See detailed comment
in source for more.

I discovered that some tests were failing when running with python 2.6 because
of changes in the behavior of int and the new print-as-a-function that Wx seems
to activate.  Updated the code to cope with both 2.5 and 2.6.

IPython/frontend/tests/test_prefilterfrontend.py

@@ -1,252 +1,266 b''
 # encoding: utf-8
 """
 Test process execution and IO redirection.
 """
 
 __docformat__ = "restructuredtext en"
 
 #-------------------------------------------------------------------------------
 #  Copyright (C) 2008  The IPython Development Team
 #
 #  Distributed under the terms of the BSD License.  The full license is
 #  in the file COPYING, distributed as part of this software.
 #-------------------------------------------------------------------------------
 
 from copy import copy, deepcopy
 from cStringIO import StringIO
 import string
+import sys
 
 from nose.tools import assert_equal
 
 from IPython.frontend.prefilterfrontend import PrefilterFrontEnd
 from IPython.ipapi import get as get_ipython0
 from IPython.testing.plugin.ipdoctest import default_argv
 
 
-def safe_deepcopy(d):
-    """ Deep copy every key of the given dict, when possible. Elsewhere
-        do a copy.
-    """
-    copied_d = dict()
-    for key, value in d.iteritems():
-        try:
-            copied_d[key] = deepcopy(value)
-        except:
-            try:
-                copied_d[key] = copy(value)
-            except:
-                copied_d[key] = value
-    return copied_d
-
-
 class TestPrefilterFrontEnd(PrefilterFrontEnd):
     
     input_prompt_template = string.Template('')
     output_prompt_template = string.Template('')
     banner = ''
 
     def __init__(self):
         self.out = StringIO()
         PrefilterFrontEnd.__init__(self,argv=default_argv())
         # Some more code for isolation (yeah, crazy)
         self._on_enter()
         self.out.flush()
         self.out.reset()
         self.out.truncate()
 
     def write(self, string, *args, **kwargs):
        self.out.write(string) 
 
     def _on_enter(self):
         self.input_buffer += '\n'
         PrefilterFrontEnd._on_enter(self)
 
 
 def isolate_ipython0(func):
     """ Decorator to isolate execution that involves an iptyhon0.
 
         Notes
         -----
 
         Apply only to functions with no arguments. Nose skips functions
         with arguments.
     """
     def my_func():
-        iplib = get_ipython0()
-        if iplib is None:
+        ip0 = get_ipython0()
+        if ip0 is None:
             return func()
-        ipython0 = iplib.IP
-        global_ns = safe_deepcopy(ipython0.user_global_ns)
-        user_ns = safe_deepcopy(ipython0.user_ns)
+        # We have a real ipython running...
+        user_ns = ip0.IP.user_ns
+        user_global_ns = ip0.IP.user_global_ns
+
+        # Previously the isolation was attempted with a deep copy of the user
+        # dicts, but we found cases where this didn't work correctly. I'm not
+        # quite sure why, but basically it did damage the user namespace, such
+        # that later tests stopped working correctly.  Instead we use a simpler
+        # approach, just computing the list of added keys to the namespace and
+        # eliminating those afterwards.  Existing keys that may have been
+        # modified remain modified.  So far this has proven to be robust.
+
+        # Compute set of old local/global keys
+        old_locals = set(user_ns.keys())
+        old_globals = set(user_global_ns.keys())
         try:
             out = func()
         finally:
-            ipython0.user_ns = user_ns
-            ipython0.user_global_ns = global_ns
+            # Find new keys, and if any, remove them
+            new_locals = set(user_ns.keys()) - old_locals
+            new_globals = set(user_global_ns.keys()) - old_globals
+            for k in new_locals:
+                del user_ns[k]
+            for k in new_globals:
+                del user_global_ns[k]
         # Undo the hack at creation of PrefilterFrontEnd
         from IPython import iplib
         iplib.InteractiveShell.isthreaded = False
         return out
 
     my_func.__name__ = func.__name__
     return my_func
 
 
 @isolate_ipython0
 def test_execution():
     """ Test execution of a command.
     """
     f = TestPrefilterFrontEnd()
-    f.input_buffer = 'print 1'
+    f.input_buffer = 'print(1)'
     f._on_enter()
     out_value = f.out.getvalue()
     assert_equal(out_value, '1\n')
 
 
 @isolate_ipython0
 def test_multiline():
     """ Test execution of a multiline command.
     """
     f = TestPrefilterFrontEnd()
     f.input_buffer = 'if True:'
     f._on_enter()
     f.input_buffer += 'print 1'
     f._on_enter()
     out_value = f.out.getvalue()
     yield assert_equal, out_value, ''
     f._on_enter()
     out_value = f.out.getvalue()
     yield assert_equal, out_value, '1\n'
     f = TestPrefilterFrontEnd()
     f.input_buffer='(1 +'
     f._on_enter()
     f.input_buffer += '0)'
     f._on_enter()
     out_value = f.out.getvalue()
     yield assert_equal, out_value, ''
     f._on_enter()
     out_value = f.out.getvalue()
     yield assert_equal, out_value, '1\n'
 
 
 @isolate_ipython0
 def test_capture():
     """ Test the capture of output in different channels.
     """
     # Test on the OS-level stdout, stderr.
     f = TestPrefilterFrontEnd()
     f.input_buffer = \
             'import os; out=os.fdopen(1, "w"); out.write("1") ; out.flush()'
     f._on_enter()
     out_value = f.out.getvalue()
     yield assert_equal, out_value, '1'
     f = TestPrefilterFrontEnd()
     f.input_buffer = \
             'import os; out=os.fdopen(2, "w"); out.write("1") ; out.flush()'
     f._on_enter()
     out_value = f.out.getvalue()
     yield assert_equal, out_value, '1'
 
      
 @isolate_ipython0
 def test_magic():
     """ Test the magic expansion and history.
     
         This test is fairly fragile and will break when magics change.
     """
     f = TestPrefilterFrontEnd()
     # Before checking the interactive namespace, make sure it's clear (it can
     # otherwise pick up things stored in the user's local db)
     f.input_buffer += '%reset -f'
     f._on_enter()
     f.complete_current_input()
     # Now, run the %who magic and check output
     f.input_buffer += '%who'
     f._on_enter()
     out_value = f.out.getvalue()
     assert_equal(out_value, 'Interactive namespace is empty.\n')
 
 
 @isolate_ipython0
 def test_help():
     """ Test object inspection.
     """
     f = TestPrefilterFrontEnd()
     f.input_buffer += "def f():"
     f._on_enter()
     f.input_buffer += "'foobar'"
     f._on_enter()
     f.input_buffer += "pass"
     f._on_enter()
     f._on_enter()
     f.input_buffer += "f?"
     f._on_enter()
     assert 'traceback' not in f.last_result
     ## XXX: ipython doctest magic breaks this. I have no clue why
     #out_value = f.out.getvalue()
     #assert out_value.split()[-1] == 'foobar' 
 
 
 @isolate_ipython0
 def test_completion_simple():
     """ Test command-line completion on trivial examples.
     """
     f = TestPrefilterFrontEnd()
     f.input_buffer = 'zzza = 1'
     f._on_enter()
     f.input_buffer = 'zzzb = 2'
     f._on_enter()
     f.input_buffer = 'zz'
     f.complete_current_input()
     out_value = f.out.getvalue()
     yield assert_equal, out_value, '\nzzza zzzb '
     yield assert_equal, f.input_buffer, 'zzz'
 
 
 @isolate_ipython0
 def test_completion_parenthesis():
     """ Test command-line completion when a parenthesis is open.
     """
     f = TestPrefilterFrontEnd()
     f.input_buffer = 'zzza = 1'
     f._on_enter()
     f.input_buffer = 'zzzb = 2'
     f._on_enter()
     f.input_buffer = 'map(zz'
     f.complete_current_input()
     out_value = f.out.getvalue()
     yield assert_equal, out_value, '\nzzza zzzb '
     yield assert_equal, f.input_buffer, 'map(zzz'
 
 
 @isolate_ipython0
 def test_completion_indexing():
     """ Test command-line completion when indexing on objects.
     """
     f = TestPrefilterFrontEnd()
     f.input_buffer = 'a = [0]'
     f._on_enter()
     f.input_buffer = 'a[0].'
     f.complete_current_input()
-    assert_equal(f.input_buffer, 'a[0].__')
+
+    if sys.version_info[:2] >= (2,6):
+        # In Python 2.6, ints picked up a few non __ methods, so now there are
+        # no completions.
+        assert_equal(f.input_buffer, 'a[0].')
+    else:
+        # Right answer for 2.4/2.5
+        assert_equal(f.input_buffer, 'a[0].__')
 
 
 @isolate_ipython0
 def test_completion_equal():
     """ Test command-line completion when the delimiter is "=", not " ".
     """
     f = TestPrefilterFrontEnd()
     f.input_buffer = 'a=1.'
     f.complete_current_input()
-    assert_equal(f.input_buffer, 'a=1.__')
-
+    if sys.version_info[:2] >= (2,6):
+        # In Python 2.6, ints picked up a few non __ methods, so now there are
+        # no completions.
+        assert_equal(f.input_buffer, 'a=1.')
+    else:
+        # Right answer for 2.4/2.5
+        assert_equal(f.input_buffer, 'a=1.__')
 
 
 if __name__ == '__main__':
     test_magic()
     test_help()
     test_execution()
     test_multiline()
     test_capture()
     test_completion_simple()
     test_completion_complex()