Source code for traits.trait_errors

# (C) Copyright 2005-2023 Enthought, Inc., Austin, TX
# All rights reserved.
#
# This software is provided without warranty under the terms of the BSD
# license included in LICENSE.txt and may be redistributed only under
# the conditions described in the aforementioned license. The license
# is also available online at http://www.enthought.com/licenses/BSD.txt
#
# Thanks for using Enthought open source!

""" Defines the standard exceptions raised by the Traits package.
"""

from .trait_base import class_of


def repr_type(obj):
    """ Return a string representation of a value and its type for readable
    error messages.
    """
    the_type = type(obj)
    msg = "%r %r" % (obj, the_type)
    return msg


class TraitError(Exception):
    def __init__(self, args=None, name=None, info=None, value=None):
        if name is None:
            # If the given args is not a tuple then assume that the user
            # intended it to be the single item in a one-element tuple.
            if not isinstance(args, tuple):
                args = (args,)
            self.args = args
        else:
            # Save the information, in case the 'args' object is not the
            # correct one, and we need to regenerate the message later:
            self.name = name
            self.info = info
            self.value = value
            self.desc = None
            self.prefix = "The"
            self.set_desc(None, args)

    def set_desc(self, desc, object=None):
        if hasattr(self, "desc"):
            if desc is not None:
                self.desc = desc
            if object is not None:
                self.object = object
            self.set_args()

    def set_prefix(self, prefix):
        if hasattr(self, "prefix"):
            self.prefix = prefix
            self.set_args()

    def set_args(self):
        if self.desc is None:
            extra = ""
        else:
            extra = " specifies %s and" % self.desc
        obj = getattr(self, "object", None)

        # Note: self.args must be a tuple so be sure to leave the trailing
        # commas.
        if obj is not None:
            self.args = (
                (
                    "%s '%s' trait of %s instance%s must be %s, "
                    "but a value of %s was specified."
                    % (
                        self.prefix,
                        self.name,
                        class_of(obj),
                        extra,
                        self.info,
                        repr_type(self.value),
                    )
                ),
            )
        else:
            self.args = (
                (
                    "%s '%s' trait%s must be %s, but a value of %s was "
                    "specified."
                    % (
                        self.prefix,
                        self.name,
                        extra,
                        self.info,
                        repr_type(self.value),
                    )
                ),
            )


class TraitNotificationError(Exception):

    pass


class DelegationError(TraitError):
    def __init__(self, args):
        # .args must be a tuple.
        self.args = (args,)