decorators.py

from pandas.compat import StringIO, callable, signature
from pandas.lib import cache_readonly  # noqa
import sys
import warnings
from textwrap import dedent
from functools import wraps


def deprecate(name, alternative, alt_name=None):
    alt_name = alt_name or alternative.__name__

    def wrapper(*args, **kwargs):
        warnings.warn("%s is deprecated. Use %s instead" % (name, alt_name),
                      FutureWarning, stacklevel=2)
        return alternative(*args, **kwargs)
    return wrapper


def deprecate_kwarg(old_arg_name, new_arg_name, mapping=None, stacklevel=2):
    """Decorator to deprecate a keyword argument of a function

    Parameters
    ----------
    old_arg_name : str
        Name of argument in function to deprecate
    new_arg_name : str
        Name of prefered argument in function
    mapping : dict or callable
        If mapping is present, use it to translate old arguments to
        new arguments. A callable must do its own value checking;
        values not found in a dict will be forwarded unchanged.

    Examples
    --------
    The following deprecates 'cols', using 'columns' instead

    >>> @deprecate_kwarg(old_arg_name='cols', new_arg_name='columns')
    ... def f(columns=''):
    ...     print(columns)
    ...
    >>> f(columns='should work ok')
    should work ok
    >>> f(cols='should raise warning')
    FutureWarning: cols is deprecated, use columns instead
      warnings.warn(msg, FutureWarning)
    should raise warning
    >>> f(cols='should error', columns="can\'t pass do both")
    TypeError: Can only specify 'cols' or 'columns', not both
    >>> @deprecate_kwarg('old', 'new', {'yes': True, 'no': False})
    ... def f(new=False):
    ...     print('yes!' if new else 'no!')
    ...
    >>> f(old='yes')
    FutureWarning: old='yes' is deprecated, use new=True instead
      warnings.warn(msg, FutureWarning)
    yes!

    """
    if mapping is not None and not hasattr(mapping, 'get') and \
            not callable(mapping):
        raise TypeError("mapping from old to new argument values "
                        "must be dict or callable!")

    def _deprecate_kwarg(func):
        @wraps(func)
        def wrapper(*args, **kwargs):
            old_arg_value = kwargs.pop(old_arg_name, None)
            if old_arg_value is not None:
                if mapping is not None:
                    if hasattr(mapping, 'get'):
                        new_arg_value = mapping.get(old_arg_value,
                                                    old_arg_value)
                    else:
                        new_arg_value = mapping(old_arg_value)
                    msg = "the %s=%r keyword is deprecated, " \
                          "use %s=%r instead" % \
                          (old_arg_name, old_arg_value,
                           new_arg_name, new_arg_value)
                else:
                    new_arg_value = old_arg_value
                    msg = "the '%s' keyword is deprecated, " \
                          "use '%s' instead" % (old_arg_name, new_arg_name)

                warnings.warn(msg, FutureWarning, stacklevel=stacklevel)
                if kwargs.get(new_arg_name, None) is not None:
                    msg = ("Can only specify '%s' or '%s', not both" %
                           (old_arg_name, new_arg_name))
                    raise TypeError(msg)
                else:
                    kwargs[new_arg_name] = new_arg_value
            return func(*args, **kwargs)
        return wrapper
    return _deprecate_kwarg


# Substitution and Appender are derived from matplotlib.docstring (1.1.0)
# module http://matplotlib.org/users/license.html


class Substitution(object):
    """
    A decorator to take a function's docstring and perform string
    substitution on it.

    This decorator should be robust even if func.__doc__ is None
    (for example, if -OO was passed to the interpreter)

    Usage: construct a docstring.Substitution with a sequence or
    dictionary suitable for performing substitution; then
    decorate a suitable function with the constructed object. e.g.

    sub_author_name = Substitution(author='Jason')

    @sub_author_name
    def some_function(x):
        "%(author)s wrote this function"

    # note that some_function.__doc__ is now "Jason wrote this function"

    One can also use positional arguments.

    sub_first_last_names = Substitution('Edgar Allen', 'Poe')

    @sub_first_last_names
    def some_function(x):
        "%s %s wrote the Raven"
    """
    def __init__(self, *args, **kwargs):
        if (args and kwargs):
            raise AssertionError("Only positional or keyword args are allowed")

        self.params = args or kwargs

    def __call__(self, func):
        func.__doc__ = func.__doc__ and func.__doc__ % self.params
        return func

    def update(self, *args, **kwargs):
        "Assume self.params is a dict and update it with supplied args"
        self.params.update(*args, **kwargs)

    @classmethod
    def from_params(cls, params):
        """
        In the case where the params is a mutable sequence (list or dictionary)
        and it may change before this class is called, one may explicitly use a
        reference to the params rather than using *args or **kwargs which will
        copy the values and not reference them.
        """
        result = cls()
        result.params = params
        return result


class Appender(object):
    """
    A function decorator that will append an addendum to the docstring
    of the target function.

    This decorator should be robust even if func.__doc__ is None
    (for example, if -OO was passed to the interpreter).

    Usage: construct a docstring.Appender with a string to be joined to
    the original docstring. An optional 'join' parameter may be supplied
    which will be used to join the docstring and addendum. e.g.

    add_copyright = Appender("Copyright (c) 2009", join='\n')

    @add_copyright
    def my_dog(has='fleas'):
        "This docstring will have a copyright below"
        pass
    """
    def __init__(self, addendum, join='', indents=0):
        if indents > 0:
            self.addendum = indent(addendum, indents=indents)
        else:
            self.addendum = addendum
        self.join = join

    def __call__(self, func):
        func.__doc__ = func.__doc__ if func.__doc__ else ''
        self.addendum = self.addendum if self.addendum else ''
        docitems = [func.__doc__, self.addendum]
        func.__doc__ = dedent(self.join.join(docitems))
        return func


def indent(text, indents=1):
    if not text or not isinstance(text, str):
        return ''
    jointext = ''.join(['\n'] + ['    '] * indents)
    return jointext.join(text.split('\n'))


def suppress_stdout(f):
    def wrapped(*args, **kwargs):
        try:
            sys.stdout = StringIO()
            f(*args, **kwargs)
        finally:
            sys.stdout = sys.__stdout__

    return wrapped


class KnownFailureTest(Exception):
    """Raise this exception to mark a test as a known failing test."""
    pass


def knownfailureif(fail_condition, msg=None):
    """
    Make function raise KnownFailureTest exception if given condition is true.

    If the condition is a callable, it is used at runtime to dynamically
    make the decision. This is useful for tests that may require costly
    imports, to delay the cost until the test suite is actually executed.

    Parameters
    ----------
    fail_condition : bool or callable
        Flag to determine whether to mark the decorated test as a known
        failure (if True) or not (if False).
    msg : str, optional
        Message to give on raising a KnownFailureTest exception.
        Default is None.

    Returns
    -------
    decorator : function
        Decorator, which, when applied to a function, causes SkipTest
        to be raised when `skip_condition` is True, and the function
        to be called normally otherwise.

    Notes
    -----
    The decorator itself is decorated with the ``nose.tools.make_decorator``
    function in order to transmit function name, and various other metadata.

    """
    if msg is None:
        msg = 'Test skipped due to known failure'

    # Allow for both boolean or callable known failure conditions.
    if callable(fail_condition):
        fail_val = fail_condition
    else:
        fail_val = lambda: fail_condition

    def knownfail_decorator(f):
        # Local import to avoid a hard nose dependency and only incur the
        # import time overhead at actual test-time.
        import nose

        def knownfailer(*args, **kwargs):
            if fail_val():
                raise KnownFailureTest(msg)
            else:
                return f(*args, **kwargs)
        return nose.tools.make_decorator(f)(knownfailer)

    return knownfail_decorator


def make_signature(func):
    """
    Returns a string repr of the arg list of a func call, with any defaults

    Examples
    --------

    >>> def f(a,b,c=2) :
    >>>     return a*b*c
    >>> print(_make_signature(f))
    a,b,c=2
    """
    spec = signature(func)
    if spec.defaults is None:
        n_wo_defaults = len(spec.args)
        defaults = ('',) * n_wo_defaults
    else:
        n_wo_defaults = len(spec.args) - len(spec.defaults)
        defaults = ('',) * n_wo_defaults + spec.defaults
    args = []
    for i, (var, default) in enumerate(zip(spec.args, defaults)):
        args.append(var if default == '' else var + '=' + repr(default))
    if spec.varargs:
        args.append('*' + spec.varargs)
    if spec.keywords:
        args.append('**' + spec.keywords)
    return args, spec.args