For doctests, globals must now be a real dictionary.

IPython/testing/globalipapp.py

@@ -1,238 +1,176 b''
 """Global IPython app to support test running.
 
 We must start our own ipython object and heavily muck with it so that all the
 modifications IPython makes to system behavior don't send the doctest machinery
 into a fit.  This code should be considered a gross hack, but it gets the job
 done.
 """
 from __future__ import absolute_import
 from __future__ import print_function
 
 #-----------------------------------------------------------------------------
 #  Copyright (C) 2009-2011  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.
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 
 # stdlib
 import __builtin__ as builtin_mod
 import os
 import sys
 
 # our own
 from . import tools
 
 from IPython.core import page
 from IPython.utils import io
 from IPython.utils import py3compat
 from IPython.frontend.terminal.interactiveshell import TerminalInteractiveShell
 
 #-----------------------------------------------------------------------------
 # Functions
 #-----------------------------------------------------------------------------
 
 class StreamProxy(io.IOStream):
     """Proxy for sys.stdout/err.  This will request the stream *at call time*
     allowing for nose's Capture plugin's redirection of sys.stdout/err.
 
     Parameters
     ----------
     name : str
         The name of the stream. This will be requested anew at every call
     """
 
     def __init__(self, name):
         self.name=name
 
     @property
     def stream(self):
         return getattr(sys, self.name)
 
     def flush(self):
         self.stream.flush()
 
 # Hack to modify the %run command so we can sync the user's namespace with the
 # test globals.  Once we move over to a clean magic system, this will be done
 # with much less ugliness.
 
 class py_file_finder(object):
     def __init__(self,test_filename):
         self.test_filename = test_filename
 
     def __call__(self,name,win32=False):
         from IPython.utils.path import get_py_filename
         try:
             return get_py_filename(name,win32=win32)
         except IOError:
             test_dir = os.path.dirname(self.test_filename)
             new_path = os.path.join(test_dir,name)
             return get_py_filename(new_path,win32=win32)
 
 
 def _run_ns_sync(self,arg_s,runner=None):
     """Modified version of %run that syncs testing namespaces.
 
     This is strictly needed for running doctests that call %run.
     """
     #print('in run_ns_sync', arg_s, file=sys.stderr)  # dbg
     finder = py_file_finder(arg_s)
     return get_ipython().magic_run_ori(arg_s, runner, finder)
 
 
-class ipnsdict(dict):
-    """A special subclass of dict for use as an IPython namespace in doctests.
-
-    This subclass adds a simple checkpointing capability so that when testing
-    machinery clears it (we use it as the test execution context), it doesn't
-    get completely destroyed.
-
-    In addition, it can handle the presence of the '_' key in a special manner,
-    which is needed because of how Python's doctest machinery operates with
-    '_'.  See constructor and :meth:`update` for details.
-    """
-
-    def __init__(self,*a):
-        dict.__init__(self,*a)
-        self._savedict = {}
-        # If this flag is True, the .update() method will unconditionally
-        # remove a key named '_'.  This is so that such a dict can be used as a
-        # namespace in doctests that call '_'.
-        self.protect_underscore = False
-
-    def clear(self):
-        dict.clear(self)
-        self.update(self._savedict)
-
-    def _checkpoint(self):
-        self._savedict.clear()
-        self._savedict.update(self)
-
-    def update(self,other):
-        self._checkpoint()
-        dict.update(self,other)
-
-        if self.protect_underscore:
-            # If '_' is in the namespace, python won't set it when executing
-            # code *in doctests*, and we have multiple doctests that use '_'.
-            # So we ensure that the namespace is always 'clean' of it before
-            # it's used for test code execution.
-            # This flag is only turned on by the doctest machinery, so that
-            # normal test code can assume the _ key is updated like any other
-            # key and can test for its presence after cell executions.
-            self.pop('_', None)
-
-        # The builtins namespace must *always* be the real __builtin__ module,
-        # else weird stuff happens.  The main ipython code does have provisions
-        # to ensure this after %run, but since in this class we do some
-        # aggressive low-level cleaning of the execution namespace, we need to
-        # correct for that ourselves, to ensure consitency with the 'real'
-        # ipython.
-        self['__builtins__'] = builtin_mod
-
-    def __delitem__(self, key):
-        """Part of the test suite checks that we can release all
-        references to an object. So we need to make sure that we're not
-        keeping a reference in _savedict."""
-        dict.__delitem__(self, key)
-        try:
-            del self._savedict[key]
-        except KeyError:
-            pass
-
-
 def get_ipython():
     # This will get replaced by the real thing once we start IPython below
     return start_ipython()
 
 
 # A couple of methods to override those in the running IPython to interact
 # better with doctest (doctest captures on raw stdout, so we need to direct
 # various types of output there otherwise it will miss them).
 
 def xsys(self, cmd):
     """Replace the default system call with a capturing one for doctest.
     """
     # We use getoutput, but we need to strip it because pexpect captures
     # the trailing newline differently from commands.getoutput
     print(self.getoutput(cmd, split=False).rstrip(), end='', file=sys.stdout)
     sys.stdout.flush()
 
 
 def _showtraceback(self, etype, evalue, stb):
     """Print the traceback purely on stdout for doctest to capture it.
     """
     print(self.InteractiveTB.stb2text(stb), file=sys.stdout)
 
 
 def start_ipython():
     """Start a global IPython shell, which we need for IPython-specific syntax.
     """
     global get_ipython
 
     # This function should only ever run once!
     if hasattr(start_ipython, 'already_called'):
         return
     start_ipython.already_called = True
 
     # Store certain global objects that IPython modifies
     _displayhook = sys.displayhook
     _excepthook = sys.excepthook
     _main = sys.modules.get('__main__')
 
     # Create custom argv and namespaces for our IPython to be test-friendly
     config = tools.default_config()
 
     # Create and initialize our test-friendly IPython instance.
     shell = TerminalInteractiveShell.instance(config=config,
-                                              user_ns=ipnsdict(),
                                               )
 
     # A few more tweaks needed for playing nicely with doctests...
 
     # remove history file
     shell.tempfiles.append(config.HistoryManager.hist_file)
 
     # These traps are normally only active for interactive use, set them
     # permanently since we'll be mocking interactive sessions.
     shell.builtin_trap.activate()
 
     # Modify the IPython system call with one that uses getoutput, so that we
     # can capture subcommands and print them to Python's stdout, otherwise the
     # doctest machinery would miss them.
     shell.system = py3compat.MethodType(xsys, shell)
     
     shell._showtraceback = py3compat.MethodType(_showtraceback, shell)
 
     # IPython is ready, now clean up some global state...
 
     # Deactivate the various python system hooks added by ipython for
     # interactive convenience so we don't confuse the doctest system
     sys.modules['__main__'] = _main
     sys.displayhook = _displayhook
     sys.excepthook = _excepthook
 
     # So that ipython magics and aliases can be doctested (they work by making
     # a call into a global _ip object).  Also make the top-level get_ipython
     # now return this without recursively calling here again.
     _ip = shell
     get_ipython = _ip.get_ipython
     builtin_mod._ip = _ip
     builtin_mod.get_ipython = get_ipython
 
     # To avoid extra IPython messages during testing, suppress io.stdout/stderr
     io.stdout = StreamProxy('stdout')
     io.stderr = StreamProxy('stderr')
     
     # Override paging, so we don't require user interaction during the tests.
     def nopage(strng, start=0, screen_lines=0, pager_cmd=None):
         print(strng)
     
     page.orig_page = page.page
     page.page = nopage
 
     return _ip

IPython/testing/plugin/ipdoctest.py

@@ -1,814 +1,811 b''
 """Nose Plugin that supports IPython doctests.
 
 Limitations:
 
 - When generating examples for use as doctests, make sure that you have
   pretty-printing OFF.  This can be done either by setting the
   ``PlainTextFormatter.pprint`` option in your configuration file to  False, or
   by interactively disabling it with  %Pprint.  This is required so that IPython
   output matches that of normal Python, which is used by doctest for internal
   execution.
 
 - Do not rely on specific prompt numbers for results (such as using
   '_34==True', for example).  For IPython tests run via an external process the
   prompt numbers may be different, and IPython tests run as normal python code
   won't even have these special _NN variables set at all.
 """
 
 #-----------------------------------------------------------------------------
 # Module imports
 
 # From the standard library
-import __builtin__
+import __builtin__ as builtin_mod
 import commands
 import doctest
 import inspect
 import logging
 import os
 import re
 import sys
 import traceback
 import unittest
 
 from inspect import getmodule
 from StringIO import StringIO
 
 # We are overriding the default doctest runner, so we need to import a few
 # things from doctest directly
 from doctest import (REPORTING_FLAGS, REPORT_ONLY_FIRST_FAILURE,
                      _unittest_reportflags, DocTestRunner,
                      _extract_future_flags, pdb, _OutputRedirectingPdb,
                      _exception_traceback,
                      linecache)
 
 # Third-party modules
 import nose.core
 
 from nose.plugins import doctests, Plugin
 from nose.util import anyp, getpackage, test_address, resolve_name, tolist
 
 #-----------------------------------------------------------------------------
 # Module globals and other constants
 #-----------------------------------------------------------------------------
 
 log = logging.getLogger(__name__)
 
 
 #-----------------------------------------------------------------------------
 # Classes and functions
 #-----------------------------------------------------------------------------
 
 def is_extension_module(filename):
     """Return whether the given filename is an extension module.
 
     This simply checks that the extension is either .so or .pyd.
     """
     return os.path.splitext(filename)[1].lower() in ('.so','.pyd')
 
 
 class DocTestSkip(object):
     """Object wrapper for doctests to be skipped."""
 
     ds_skip = """Doctest to skip.
     >>> 1 #doctest: +SKIP
     """
 
     def __init__(self,obj):
         self.obj = obj
 
     def __getattribute__(self,key):
         if key == '__doc__':
             return DocTestSkip.ds_skip
         else:
             return getattr(object.__getattribute__(self,'obj'),key)
 
 # Modified version of the one in the stdlib, that fixes a python bug (doctests
 # not found in extension modules, http://bugs.python.org/issue3158)
 class DocTestFinder(doctest.DocTestFinder):
 
     def _from_module(self, module, object):
         """
         Return true if the given object is defined in the given
         module.
         """
         if module is None:
             return True
         elif inspect.isfunction(object):
             return module.__dict__ is object.func_globals
         elif inspect.isbuiltin(object):
             return module.__name__ == object.__module__
         elif inspect.isclass(object):
             return module.__name__ == object.__module__
         elif inspect.ismethod(object):
             # This one may be a bug in cython that fails to correctly set the
             # __module__ attribute of methods, but since the same error is easy
             # to make by extension code writers, having this safety in place
             # isn't such a bad idea
             return module.__name__ == object.im_class.__module__
         elif inspect.getmodule(object) is not None:
             return module is inspect.getmodule(object)
         elif hasattr(object, '__module__'):
             return module.__name__ == object.__module__
         elif isinstance(object, property):
             return True # [XX] no way not be sure.
         else:
             raise ValueError("object must be a class or function")
 
     def _find(self, tests, obj, name, module, source_lines, globs, seen):
         """
         Find tests for the given object and any contained objects, and
         add them to `tests`.
         """
         #print '_find for:', obj, name, module  # dbg
         if hasattr(obj,"skip_doctest"):
             #print 'SKIPPING DOCTEST FOR:',obj  # dbg
             obj = DocTestSkip(obj)
 
         doctest.DocTestFinder._find(self,tests, obj, name, module,
                                     source_lines, globs, seen)
 
         # Below we re-run pieces of the above method with manual modifications,
         # because the original code is buggy and fails to correctly identify
         # doctests in extension modules.
 
         # Local shorthands
         from inspect import isroutine, isclass, ismodule
 
         # Look for tests in a module's contained objects.
         if inspect.ismodule(obj) and self._recurse:
             for valname, val in obj.__dict__.items():
                 valname1 = '%s.%s' % (name, valname)
                 if ( (isroutine(val) or isclass(val))
                      and self._from_module(module, val) ):
 
                     self._find(tests, val, valname1, module, source_lines,
                                globs, seen)
 
         # Look for tests in a class's contained objects.
         if inspect.isclass(obj) and self._recurse:
             #print 'RECURSE into class:',obj  # dbg
             for valname, val in obj.__dict__.items():
                 # Special handling for staticmethod/classmethod.
                 if isinstance(val, staticmethod):
                     val = getattr(obj, valname)
                 if isinstance(val, classmethod):
                     val = getattr(obj, valname).im_func
 
                 # Recurse to methods, properties, and nested classes.
                 if ((inspect.isfunction(val) or inspect.isclass(val) or
                      inspect.ismethod(val) or
                       isinstance(val, property)) and
                       self._from_module(module, val)):
                     valname = '%s.%s' % (name, valname)
                     self._find(tests, val, valname, module, source_lines,
                                globs, seen)
 
 
 class IPDoctestOutputChecker(doctest.OutputChecker):
     """Second-chance checker with support for random tests.
 
     If the default comparison doesn't pass, this checker looks in the expected
     output string for flags that tell us to ignore the output.
     """
 
     random_re = re.compile(r'#\s*random\s+')
 
     def check_output(self, want, got, optionflags):
         """Check output, accepting special markers embedded in the output.
 
         If the output didn't pass the default validation but the special string
         '#random' is included, we accept it."""
 
         # Let the original tester verify first, in case people have valid tests
         # that happen to have a comment saying '#random' embedded in.
         ret = doctest.OutputChecker.check_output(self, want, got,
                                                  optionflags)
         if not ret and self.random_re.search(want):
             #print >> sys.stderr, 'RANDOM OK:',want  # dbg
             return True
 
         return ret
 
 
 class DocTestCase(doctests.DocTestCase):
     """Proxy for DocTestCase: provides an address() method that
     returns the correct address for the doctest case. Otherwise
     acts as a proxy to the test case. To provide hints for address(),
     an obj may also be passed -- this will be used as the test object
     for purposes of determining the test address, if it is provided.
     """
 
     # Note: this method was taken from numpy's nosetester module.
 
     # Subclass nose.plugins.doctests.DocTestCase to work around a bug in
     # its constructor that blocks non-default arguments from being passed
     # down into doctest.DocTestCase
 
     def __init__(self, test, optionflags=0, setUp=None, tearDown=None,
                  checker=None, obj=None, result_var='_'):
         self._result_var = result_var
         doctests.DocTestCase.__init__(self, test,
                                       optionflags=optionflags,
                                       setUp=setUp, tearDown=tearDown,
                                       checker=checker)
         # Now we must actually copy the original constructor from the stdlib
         # doctest class, because we can't call it directly and a bug in nose
         # means it never gets passed the right arguments.
 
         self._dt_optionflags = optionflags
         self._dt_checker = checker
         self._dt_test = test
         self._dt_test_globs_ori = test.globs
         self._dt_setUp = setUp
         self._dt_tearDown = tearDown
 
         # XXX - store this runner once in the object!
         runner = IPDocTestRunner(optionflags=optionflags,
                                  checker=checker, verbose=False)
         self._dt_runner = runner
 
 
         # Each doctest should remember the directory it was loaded from, so
         # things like %run work without too many contortions
         self._ori_dir = os.path.dirname(test.filename)
 
     # Modified runTest from the default stdlib
     def runTest(self):
         test = self._dt_test
         runner = self._dt_runner
 
         old = sys.stdout
         new = StringIO()
         optionflags = self._dt_optionflags
 
         if not (optionflags & REPORTING_FLAGS):
             # The option flags don't include any reporting flags,
             # so add the default reporting flags
             optionflags |= _unittest_reportflags
 
         try:
             # Save our current directory and switch out to the one where the
             # test was originally created, in case another doctest did a
             # directory change.  We'll restore this in the finally clause.
             curdir = os.getcwdu()
             #print 'runTest in dir:', self._ori_dir  # dbg
             os.chdir(self._ori_dir)
 
             runner.DIVIDER = "-"*70
             failures, tries = runner.run(test,out=new.write,
                                          clear_globs=False)
         finally:
             sys.stdout = old
             os.chdir(curdir)
 
         if failures:
             raise self.failureException(self.format_failure(new.getvalue()))
 
     def setUp(self):
         """Modified test setup that syncs with ipython namespace"""
         #print "setUp test", self._dt_test.examples # dbg
-        if isinstance(self._dt_test.examples[0],IPExample):
+        if isinstance(self._dt_test.examples[0], IPExample):
             # for IPython examples *only*, we swap the globals with the ipython
             # namespace, after updating it with the globals (which doctest
             # fills with the necessary info from the module being tested).
             self.user_ns_orig = {}
             self.user_ns_orig.update(_ip.user_ns)
             _ip.user_ns.update(self._dt_test.globs)
+            # We must remove the _ key in the namespace, so that Python's
+            # doctest code sets it naturally
+            _ip.user_ns.pop('_', None)
+            _ip.user_ns['__builtins__'] = builtin_mod
             self._dt_test.globs = _ip.user_ns
-            # IPython must protect the _ key in the namespace (it can't exist)
-            # so that Python's doctest code sets it naturally, so we enable
-            # this feature of our testing namespace.
-            _ip.user_ns.protect_underscore = True
 
         super(DocTestCase, self).setUp()
 
     def tearDown(self):
 
         # Undo the test.globs reassignment we made, so that the parent class
         # teardown doesn't destroy the ipython namespace
-        if isinstance(self._dt_test.examples[0],IPExample):
+        if isinstance(self._dt_test.examples[0], IPExample):
             self._dt_test.globs = self._dt_test_globs_ori
             _ip.user_ns.clear()
             _ip.user_ns.update(self.user_ns_orig)
-            # Restore the behavior of the '_' key in the user namespace to
-            # normal after each doctest, so that unittests behave normally
-            _ip.user_ns.protect_underscore = False
 
         # XXX - fperez: I am not sure if this is truly a bug in nose 0.11, but
         # it does look like one to me: its tearDown method tries to run
         #
         # delattr(__builtin__, self._result_var)
         #
         # without checking that the attribute really is there; it implicitly
         # assumes it should have been set via displayhook.  But if the
         # displayhook was never called, this doesn't necessarily happen.  I
         # haven't been able to find a little self-contained example outside of
         # ipython that would show the problem so I can report it to the nose
         # team, but it does happen a lot in our code.
         #
         # So here, we just protect as narrowly as possible by trapping an
         # attribute error whose message would be the name of self._result_var,
         # and letting any other error propagate.
         try:
             super(DocTestCase, self).tearDown()
         except AttributeError, exc:
             if exc.args[0] != self._result_var:
                 raise
 
 
 # A simple subclassing of the original with a different class name, so we can
 # distinguish and treat differently IPython examples from pure python ones.
 class IPExample(doctest.Example): pass
 
 
 class IPExternalExample(doctest.Example):
     """Doctest examples to be run in an external process."""
 
     def __init__(self, source, want, exc_msg=None, lineno=0, indent=0,
                  options=None):
         # Parent constructor
         doctest.Example.__init__(self,source,want,exc_msg,lineno,indent,options)
 
         # An EXTRA newline is needed to prevent pexpect hangs
         self.source += '\n'
 
 
 class IPDocTestParser(doctest.DocTestParser):
     """
     A class used to parse strings containing doctest examples.
 
     Note: This is a version modified to properly recognize IPython input and
     convert any IPython examples into valid Python ones.
     """
     # This regular expression is used to find doctest examples in a
     # string.  It defines three groups: `source` is the source code
     # (including leading indentation and prompts); `indent` is the
     # indentation of the first (PS1) line of the source code; and
     # `want` is the expected output (including leading indentation).
 
     # Classic Python prompts or default IPython ones
     _PS1_PY = r'>>>'
     _PS2_PY = r'\.\.\.'
 
     _PS1_IP = r'In\ \[\d+\]:'
     _PS2_IP = r'\ \ \ \.\.\.+:'
 
     _RE_TPL = r'''
         # Source consists of a PS1 line followed by zero or more PS2 lines.
         (?P<source>
             (?:^(?P<indent> [ ]*) (?P<ps1> %s) .*)    # PS1 line
             (?:\n           [ ]*  (?P<ps2> %s) .*)*)  # PS2 lines
         \n? # a newline
         # Want consists of any non-blank lines that do not start with PS1.
         (?P<want> (?:(?![ ]*$)    # Not a blank line
                      (?![ ]*%s)   # Not a line starting with PS1
                      (?![ ]*%s)   # Not a line starting with PS2
                      .*$\n?       # But any other line
                   )*)
                   '''
 
     _EXAMPLE_RE_PY = re.compile( _RE_TPL % (_PS1_PY,_PS2_PY,_PS1_PY,_PS2_PY),
                                  re.MULTILINE | re.VERBOSE)
 
     _EXAMPLE_RE_IP = re.compile( _RE_TPL % (_PS1_IP,_PS2_IP,_PS1_IP,_PS2_IP),
                                  re.MULTILINE | re.VERBOSE)
 
     # Mark a test as being fully random.  In this case, we simply append the
     # random marker ('#random') to each individual example's output.  This way
     # we don't need to modify any other code.
     _RANDOM_TEST = re.compile(r'#\s*all-random\s+')
 
     # Mark tests to be executed in an external process - currently unsupported.
     _EXTERNAL_IP = re.compile(r'#\s*ipdoctest:\s*EXTERNAL')
 
     def ip2py(self,source):
         """Convert input IPython source into valid Python."""
         out = []
         newline = out.append
         #print 'IPSRC:\n',source,'\n###'  # dbg
         # The input source must be first stripped of all bracketing whitespace
         # and turned into lines, so it looks to the parser like regular user
         # input
         for lnum,line in enumerate(source.strip().splitlines()):
             newline(_ip.prefilter(line,lnum>0))
         newline('')  # ensure a closing newline, needed by doctest
         #print "PYSRC:", '\n'.join(out)  # dbg
         return '\n'.join(out)
 
     def parse(self, string, name='<string>'):
         """
         Divide the given string into examples and intervening text,
         and return them as a list of alternating Examples and strings.
         Line numbers for the Examples are 0-based.  The optional
         argument `name` is a name identifying this string, and is only
         used for error messages.
         """
 
         #print 'Parse string:\n',string # dbg
 
         string = string.expandtabs()
         # If all lines begin with the same indentation, then strip it.
         min_indent = self._min_indent(string)
         if min_indent > 0:
             string = '\n'.join([l[min_indent:] for l in string.split('\n')])
 
         output = []
         charno, lineno = 0, 0
 
         # We make 'all random' tests by adding the '# random' mark to every
         # block of output in the test.
         if self._RANDOM_TEST.search(string):
             random_marker = '\n# random'
         else:
             random_marker = ''
 
         # Whether to convert the input from ipython to python syntax
         ip2py = False
         # Find all doctest examples in the string.  First, try them as Python
         # examples, then as IPython ones
         terms = list(self._EXAMPLE_RE_PY.finditer(string))
         if terms:
             # Normal Python example
             #print '-'*70  # dbg
             #print 'PyExample, Source:\n',string  # dbg
             #print '-'*70  # dbg
             Example = doctest.Example
         else:
             # It's an ipython example.  Note that IPExamples are run
             # in-process, so their syntax must be turned into valid python.
             # IPExternalExamples are run out-of-process (via pexpect) so they
             # don't need any filtering (a real ipython will be executing them).
             terms = list(self._EXAMPLE_RE_IP.finditer(string))
             if self._EXTERNAL_IP.search(string):
                 #print '-'*70  # dbg
                 #print 'IPExternalExample, Source:\n',string  # dbg
                 #print '-'*70  # dbg
                 Example = IPExternalExample
             else:
                 #print '-'*70  # dbg
                 #print 'IPExample, Source:\n',string  # dbg
                 #print '-'*70  # dbg
                 Example = IPExample
                 ip2py = True
 
         for m in terms:
             # Add the pre-example text to `output`.
             output.append(string[charno:m.start()])
             # Update lineno (lines before this example)
             lineno += string.count('\n', charno, m.start())
             # Extract info from the regexp match.
             (source, options, want, exc_msg) = \
                      self._parse_example(m, name, lineno,ip2py)
 
             # Append the random-output marker (it defaults to empty in most
             # cases, it's only non-empty for 'all-random' tests):
             want += random_marker
 
             if Example is IPExternalExample:
                 options[doctest.NORMALIZE_WHITESPACE] = True
                 want += '\n'
 
             # Create an Example, and add it to the list.
             if not self._IS_BLANK_OR_COMMENT(source):
                 output.append(Example(source, want, exc_msg,
                                       lineno=lineno,
                                       indent=min_indent+len(m.group('indent')),
                                       options=options))
             # Update lineno (lines inside this example)
             lineno += string.count('\n', m.start(), m.end())
             # Update charno.
             charno = m.end()
         # Add any remaining post-example text to `output`.
         output.append(string[charno:])
         return output
 
     def _parse_example(self, m, name, lineno,ip2py=False):
         """
         Given a regular expression match from `_EXAMPLE_RE` (`m`),
         return a pair `(source, want)`, where `source` is the matched
         example's source code (with prompts and indentation stripped);
         and `want` is the example's expected output (with indentation
         stripped).
 
         `name` is the string's name, and `lineno` is the line number
         where the example starts; both are used for error messages.
 
         Optional:
         `ip2py`: if true, filter the input via IPython to convert the syntax
         into valid python.
         """
 
         # Get the example's indentation level.
         indent = len(m.group('indent'))
 
         # Divide source into lines; check that they're properly
         # indented; and then strip their indentation & prompts.
         source_lines = m.group('source').split('\n')
 
         # We're using variable-length input prompts
         ps1 = m.group('ps1')
         ps2 = m.group('ps2')
         ps1_len = len(ps1)
 
         self._check_prompt_blank(source_lines, indent, name, lineno,ps1_len)
         if ps2:
             self._check_prefix(source_lines[1:], ' '*indent + ps2, name, lineno)
 
         source = '\n'.join([sl[indent+ps1_len+1:] for sl in source_lines])
 
         if ip2py:
             # Convert source input from IPython into valid Python syntax
             source = self.ip2py(source)
 
         # Divide want into lines; check that it's properly indented; and
         # then strip the indentation.  Spaces before the last newline should
         # be preserved, so plain rstrip() isn't good enough.
         want = m.group('want')
         want_lines = want.split('\n')
         if len(want_lines) > 1 and re.match(r' *$', want_lines[-1]):
             del want_lines[-1]  # forget final newline & spaces after it
         self._check_prefix(want_lines, ' '*indent, name,
                            lineno + len(source_lines))
 
         # Remove ipython output prompt that might be present in the first line
         want_lines[0] = re.sub(r'Out\[\d+\]: \s*?\n?','',want_lines[0])
 
         want = '\n'.join([wl[indent:] for wl in want_lines])
 
         # If `want` contains a traceback message, then extract it.
         m = self._EXCEPTION_RE.match(want)
         if m:
             exc_msg = m.group('msg')
         else:
             exc_msg = None
 
         # Extract options from the source.
         options = self._find_options(source, name, lineno)
 
         return source, options, want, exc_msg
 
     def _check_prompt_blank(self, lines, indent, name, lineno, ps1_len):
         """
         Given the lines of a source string (including prompts and
         leading indentation), check to make sure that every prompt is
         followed by a space character.  If any line is not followed by
         a space character, then raise ValueError.
 
         Note: IPython-modified version which takes the input prompt length as a
         parameter, so that prompts of variable length can be dealt with.
         """
         space_idx = indent+ps1_len
         min_len = space_idx+1
         for i, line in enumerate(lines):
             if len(line) >=  min_len and line[space_idx] != ' ':
                 raise ValueError('line %r of the docstring for %s '
                                  'lacks blank after %s: %r' %
                                  (lineno+i+1, name,
                                   line[indent:space_idx], line))
 
 
 SKIP = doctest.register_optionflag('SKIP')
 
 
 class IPDocTestRunner(doctest.DocTestRunner,object):
     """Test runner that synchronizes the IPython namespace with test globals.
     """
 
     def run(self, test, compileflags=None, out=None, clear_globs=True):
 
         # Hack: ipython needs access to the execution context of the example,
         # so that it can propagate user variables loaded by %run into
         # test.globs.  We put them here into our modified %run as a function
         # attribute.  Our new %run will then only make the namespace update
         # when called (rather than unconconditionally updating test.globs here
         # for all examples, most of which won't be calling %run anyway).
         #_ip._ipdoctest_test_globs = test.globs
         #_ip._ipdoctest_test_filename = test.filename
 
         test.globs.update(_ip.user_ns)
 
         return super(IPDocTestRunner,self).run(test,
                                                compileflags,out,clear_globs)
 
 
 class DocFileCase(doctest.DocFileCase):
     """Overrides to provide filename
     """
     def address(self):
         return (self._dt_test.filename, None, None)
 
 
 class ExtensionDoctest(doctests.Doctest):
     """Nose Plugin that supports doctests in extension modules.
     """
     name = 'extdoctest'   # call nosetests with --with-extdoctest
     enabled = True
 
     def __init__(self,exclude_patterns=None):
         """Create a new ExtensionDoctest plugin.
 
         Parameters
         ----------
 
         exclude_patterns : sequence of strings, optional
           These patterns are compiled as regular expressions, subsequently used
           to exclude any filename which matches them from inclusion in the test
           suite (using pattern.search(), NOT pattern.match() ).
         """
 
         if exclude_patterns is None:
             exclude_patterns = []
         self.exclude_patterns = map(re.compile,exclude_patterns)
         doctests.Doctest.__init__(self)
 
     def options(self, parser, env=os.environ):
         Plugin.options(self, parser, env)
         parser.add_option('--doctest-tests', action='store_true',
                           dest='doctest_tests',
                           default=env.get('NOSE_DOCTEST_TESTS',True),
                           help="Also look for doctests in test modules. "
                           "Note that classes, methods and functions should "
                           "have either doctests or non-doctest tests, "
                           "not both. [NOSE_DOCTEST_TESTS]")
         parser.add_option('--doctest-extension', action="append",
                           dest="doctestExtension",
                           help="Also look for doctests in files with "
                           "this extension [NOSE_DOCTEST_EXTENSION]")
         # Set the default as a list, if given in env; otherwise
         # an additional value set on the command line will cause
         # an error.
         env_setting = env.get('NOSE_DOCTEST_EXTENSION')
         if env_setting is not None:
             parser.set_defaults(doctestExtension=tolist(env_setting))
 
 
     def configure(self, options, config):
         Plugin.configure(self, options, config)
         # Pull standard doctest plugin out of config; we will do doctesting
         config.plugins.plugins = [p for p in config.plugins.plugins
                                   if p.name != 'doctest']
         self.doctest_tests = options.doctest_tests
         self.extension = tolist(options.doctestExtension)
 
         self.parser = doctest.DocTestParser()
         self.finder = DocTestFinder()
         self.checker = IPDoctestOutputChecker()
         self.globs = None
         self.extraglobs = None
 
 
     def loadTestsFromExtensionModule(self,filename):
         bpath,mod = os.path.split(filename)
         modname = os.path.splitext(mod)[0]
         try:
             sys.path.append(bpath)
             module = __import__(modname)
             tests = list(self.loadTestsFromModule(module))
         finally:
             sys.path.pop()
         return tests
 
     # NOTE: the method below is almost a copy of the original one in nose, with
     # a  few modifications to control output checking.
 
     def loadTestsFromModule(self, module):
         #print '*** ipdoctest - lTM',module  # dbg
 
         if not self.matches(module.__name__):
             log.debug("Doctest doesn't want module %s", module)
             return
 
         tests = self.finder.find(module,globs=self.globs,
                                  extraglobs=self.extraglobs)
         if not tests:
             return
 
         # always use whitespace and ellipsis options
         optionflags = doctest.NORMALIZE_WHITESPACE | doctest.ELLIPSIS
 
         tests.sort()
         module_file = module.__file__
         if module_file[-4:] in ('.pyc', '.pyo'):
             module_file = module_file[:-1]
         for test in tests:
             if not test.examples:
                 continue
             if not test.filename:
                 test.filename = module_file
 
             yield DocTestCase(test,
                               optionflags=optionflags,
                               checker=self.checker)
 
 
     def loadTestsFromFile(self, filename):
         #print "ipdoctest - from file", filename # dbg
         if is_extension_module(filename):
             for t in self.loadTestsFromExtensionModule(filename):
                 yield t
         else:
             if self.extension and anyp(filename.endswith, self.extension):
                 name = os.path.basename(filename)
                 dh = open(filename)
                 try:
                     doc = dh.read()
                 finally:
                     dh.close()
                 test = self.parser.get_doctest(
                     doc, globs={'__file__': filename}, name=name,
                     filename=filename, lineno=0)
                 if test.examples:
                     #print 'FileCase:',test.examples  # dbg
                     yield DocFileCase(test)
                 else:
                     yield False # no tests to load
 
     def wantFile(self,filename):
         """Return whether the given filename should be scanned for tests.
 
         Modified version that accepts extension modules as valid containers for
         doctests.
         """
         #print '*** ipdoctest- wantFile:',filename  # dbg
 
         for pat in self.exclude_patterns:
             if pat.search(filename):
                 # print '###>>> SKIP:',filename  # dbg
                 return False
 
         if is_extension_module(filename):
             return True
         else:
             return doctests.Doctest.wantFile(self,filename)
 
     def wantDirectory(self, directory):
         """Return whether the given directory should be scanned for tests.
 
         Modified version that supports exclusions.
         """
 
         for pat in self.exclude_patterns:
             if pat.search(directory):
                 return False
         return True
 
 
 class IPythonDoctest(ExtensionDoctest):
     """Nose Plugin that supports doctests in extension modules.
     """
     name = 'ipdoctest'   # call nosetests with --with-ipdoctest
     enabled = True
 
     def makeTest(self, obj, parent):
         """Look for doctests in the given object, which will be a
         function, method or class.
         """
         #print 'Plugin analyzing:', obj, parent  # dbg
         # always use whitespace and ellipsis options
         optionflags = doctest.NORMALIZE_WHITESPACE | doctest.ELLIPSIS
 
         doctests = self.finder.find(obj, module=getmodule(parent))
         if doctests:
             for test in doctests:
                 if len(test.examples) == 0:
                     continue
 
                 yield DocTestCase(test, obj=obj,
                                   optionflags=optionflags,
                                   checker=self.checker)
 
     def options(self, parser, env=os.environ):
         #print "Options for nose plugin:", self.name # dbg
         Plugin.options(self, parser, env)
         parser.add_option('--ipdoctest-tests', action='store_true',
                           dest='ipdoctest_tests',
                           default=env.get('NOSE_IPDOCTEST_TESTS',True),
                           help="Also look for doctests in test modules. "
                           "Note that classes, methods and functions should "
                           "have either doctests or non-doctest tests, "
                           "not both. [NOSE_IPDOCTEST_TESTS]")
         parser.add_option('--ipdoctest-extension', action="append",
                           dest="ipdoctest_extension",
                           help="Also look for doctests in files with "
                           "this extension [NOSE_IPDOCTEST_EXTENSION]")
         # Set the default as a list, if given in env; otherwise
         # an additional value set on the command line will cause
         # an error.
         env_setting = env.get('NOSE_IPDOCTEST_EXTENSION')
         if env_setting is not None:
             parser.set_defaults(ipdoctest_extension=tolist(env_setting))
 
     def configure(self, options, config):
         #print "Configuring nose plugin:", self.name # dbg
         Plugin.configure(self, options, config)
         # Pull standard doctest plugin out of config; we will do doctesting
         config.plugins.plugins = [p for p in config.plugins.plugins
                                   if p.name != 'doctest']
         self.doctest_tests = options.ipdoctest_tests
         self.extension = tolist(options.ipdoctest_extension)
 
         self.parser = IPDocTestParser()
         self.finder = DocTestFinder(parser=self.parser)
         self.checker = IPDoctestOutputChecker()
         self.globs = None
         self.extraglobs = None