PyLg/pylg/dummy.py

# -----------------------------------------------------------------------------
# PyLg: module to facilitate and automate the process of writing runtime logs.
# Copyright (C) 2017 Wojciech Kozlowski <wk@wojciechkozlowski.eu>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.
# -----------------------------------------------------------------------------

from functools import partial
from .pylg import TraceFunction


class TraceFunctionDummy(TraceFunction):

    """ Dummy implementation of TraceFunction.
    """

    def __init__(self, *args, **kwargs):

        """ Constructor for dummy TraceFunction.
        """

        # ---------------------------------------------------------------------
        # Rather than having an entirely empty dummy class, we call
        # the superclass constructor to have input verification even
        # when PyLg is disabled.
        # ---------------------------------------------------------------------
        super(TraceFunctionDummy, self).__init__(*args, **kwargs)

    def __call__(self, *args, **kwargs):

        """ The actual wrapper that is called when a call to a
            decorated function is made. It also handles extra
            initialisation when parameters are passed to
            TraceFunction.

            :return: The return value of the decorated function.
        """

        if self.function is None:
            # -----------------------------------------------------------------
            # For an explanation of the logic here, see the non-dummy
            # implementations in pylg.py.
            # -----------------------------------------------------------------
            self.init_function(*args, **kwargs)
            return self

        # ---------------------------------------------------------------------
        # The actual decorating. The dummy implementation doesn't do anything.
        # ---------------------------------------------------------------------
        return self.function(*args, **kwargs)

    def init_function(self, *args, **kwargs):

        """ Function to initialise the TraceFunctionStruct kept by the
            decorator.
        """

        # ---------------------------------------------------------------------
        # This function should only ever be called with one parameter
        # - the function to be decorated. These checks are done here,
        # rather than by the caller, as anything that calls this
        # function should also have been called with the decorated
        # function as its only parameter.
        # ---------------------------------------------------------------------
        assert not kwargs
        assert len(args) == 1
        assert callable(args[0])

        self.function = args[0]


def trace(message, function=None):
    pass