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"""utilities for testing IPython kernels"""

#-------------------------------------------------------------------------------

# Copyright (C) 2013 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

#-------------------------------------------------------------------------------

import atexit

from contextlib import contextmanager

from subprocess import PIPE, STDOUT

try:

from queue import Empty # Py 3

except ImportError:

from Queue import Empty # Py 2

import nose

import nose.tools as nt

from IPython.kernel import KernelManager

#-------------------------------------------------------------------------------

# Globals

#-------------------------------------------------------------------------------

STARTUP_TIMEOUT = 60

TIMEOUT = 15

KM = None

KC = None

#-------------------------------------------------------------------------------

# code

#-------------------------------------------------------------------------------

def start_new_kernel(argv=None):

"""start a new kernel, and return its Manager and Client"""

km = KernelManager()

kwargs = dict(stdout=PIPE, stderr=STDOUT)

if argv:

kwargs['extra_arguments'] = argv

km.start_kernel(**kwargs)

nose.ipy_stream_capturer.add_stream(km.kernel.stdout.fileno())

nose.ipy_stream_capturer.ensure_started()

kc = km.client()

kc.start_channels()

msg_id = kc.kernel_info()

kc.get_shell_msg(block=True, timeout=STARTUP_TIMEOUT)

flush_channels(kc)

return km, kc

def flush_channels(kc=None):

"""flush any messages waiting on the queue"""

from .test_message_spec import validate_message

if kc is None:

kc = KC

for channel in (kc.shell_channel, kc.iopub_channel):

while True:

try:

msg = channel.get_msg(block=True, timeout=0.1)

except Empty:

break

else:

validate_message(msg)

def execute(code='', kc=None, **kwargs):

"""wrapper for doing common steps for validating an execution request"""

from .test_message_spec import validate_message

if kc is None:

kc = KC

msg_id = kc.execute(code=code, **kwargs)

reply = kc.get_shell_msg(timeout=TIMEOUT)

validate_message(reply, 'execute_reply', msg_id)

busy = kc.get_iopub_msg(timeout=TIMEOUT)

validate_message(busy, 'status', msg_id)

nt.assert_equal(busy['content']['execution_state'], 'busy')

if not kwargs.get('silent'):

pyin = kc.get_iopub_msg(timeout=TIMEOUT)

validate_message(pyin, 'pyin', msg_id)

nt.assert_equal(pyin['content']['code'], code)

return msg_id, reply['content']

def start_global_kernel():

"""start the global kernel (if it isn't running) and return its client"""

global KM, KC

if KM is None:

KM, KC = start_new_kernel()

atexit.register(stop_global_kernel)

return KC

@contextmanager

def kernel():

"""Context manager for the global kernel instance

Should be used for most kernel tests

Returns

-------

kernel_client: connected KernelClient instance

"""

yield start_global_kernel()

def uses_kernel(test_f):

"""Decorator for tests that use the global kernel"""

def wrapped_test():

with kernel() as kc:

test_f(kc)

wrapped_test.__doc__ = test_f.__doc__

wrapped_test.__name__ = test_f.__name__

return wrapped_test

def stop_global_kernel():

"""Stop the global shared kernel instance, if it exists"""

global KM, KC

KC.stop_channels()

KC = None

if KM is None:

return

KM.shutdown_kernel(now=True)

KM = None

@contextmanager

def new_kernel(argv=None):

"""Context manager for a new kernel in a subprocess

Should only be used for tests where the kernel must not be re-used.

Returns

-------

kernel_client: connected KernelClient instance

"""

km, kc = start_new_kernel(argv)

try:

yield kc

finally:

kc.stop_channels()

km.shutdown_kernel(now=True)

def assemble_output(iopub):

"""assemble stdout/err from an execution"""

stdout = ''

stderr = ''

while True:

msg = iopub.get_msg(block=True, timeout=1)

msg_type = msg['msg_type']

content = msg['content']

if msg_type == 'status' and content['execution_state'] == 'idle':

# idle message signals end of output

break

elif msg['msg_type'] == 'stream':

if content['name'] == 'stdout':

stdout += content['data']

elif content['name'] == 'stderr':

stderr += content['data']

else:

raise KeyError("bad stream: %r" % content['name'])

else:

# other output, ignored

pass

return stdout, stderr