globalipapp.py

"""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 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.utils.py3compat import builtin_mod
from IPython.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()


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, depth=1).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,
                                              )

    # 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.pager_page
    page.pager_page = nopage

    return _ip