openmedialibrary_platform_linux32/lib/python3.4/site-packages/sqlalchemy/sql/annotation.py

# sql/annotation.py
# Copyright (C) 2005-2016 the SQLAlchemy authors and contributors
# <see AUTHORS file>
#
# This module is part of SQLAlchemy and is released under
# the MIT License: http://www.opensource.org/licenses/mit-license.php

"""The :class:`.Annotated` class and related routines; creates hash-equivalent
copies of SQL constructs which contain context-specific markers and
associations.

"""

from .. import util
from . import operators


class Annotated(object):
    """clones a ClauseElement and applies an 'annotations' dictionary.

    Unlike regular clones, this clone also mimics __hash__() and
    __cmp__() of the original element so that it takes its place
    in hashed collections.

    A reference to the original element is maintained, for the important
    reason of keeping its hash value current.  When GC'ed, the
    hash value may be reused, causing conflicts.

    """

    def __new__(cls, *args):
        if not args:
            # clone constructor
            return object.__new__(cls)
        else:
            element, values = args
            # pull appropriate subclass from registry of annotated
            # classes
            try:
                cls = annotated_classes[element.__class__]
            except KeyError:
                cls = _new_annotation_type(element.__class__, cls)
            return object.__new__(cls)

    def __init__(self, element, values):
        self.__dict__ = element.__dict__.copy()
        self.__element = element
        self._annotations = values
        self._hash = hash(element)

    def _annotate(self, values):
        _values = self._annotations.copy()
        _values.update(values)
        return self._with_annotations(_values)

    def _with_annotations(self, values):
        clone = self.__class__.__new__(self.__class__)
        clone.__dict__ = self.__dict__.copy()
        clone._annotations = values
        return clone

    def _deannotate(self, values=None, clone=True):
        if values is None:
            return self.__element
        else:
            _values = self._annotations.copy()
            for v in values:
                _values.pop(v, None)
            return self._with_annotations(_values)

    def _compiler_dispatch(self, visitor, **kw):
        return self.__element.__class__._compiler_dispatch(
            self, visitor, **kw)

    @property
    def _constructor(self):
        return self.__element._constructor

    def _clone(self):
        clone = self.__element._clone()
        if clone is self.__element:
            # detect immutable, don't change anything
            return self
        else:
            # update the clone with any changes that have occurred
            # to this object's __dict__.
            clone.__dict__.update(self.__dict__)
            return self.__class__(clone, self._annotations)

    def __hash__(self):
        return self._hash

    def __eq__(self, other):
        if isinstance(self.__element, operators.ColumnOperators):
            return self.__element.__class__.__eq__(self, other)
        else:
            return hash(other) == hash(self)


# hard-generate Annotated subclasses.  this technique
# is used instead of on-the-fly types (i.e. type.__new__())
# so that the resulting objects are pickleable.
annotated_classes = {}


def _deep_annotate(element, annotations, exclude=None):
    """Deep copy the given ClauseElement, annotating each element
    with the given annotations dictionary.

    Elements within the exclude collection will be cloned but not annotated.

    """
    def clone(elem):
        if exclude and \
                hasattr(elem, 'proxy_set') and \
                elem.proxy_set.intersection(exclude):
            newelem = elem._clone()
        elif annotations != elem._annotations:
            newelem = elem._annotate(annotations)
        else:
            newelem = elem
        newelem._copy_internals(clone=clone)
        return newelem

    if element is not None:
        element = clone(element)
    return element


def _deep_deannotate(element, values=None):
    """Deep copy the given element, removing annotations."""

    cloned = util.column_dict()

    def clone(elem):
        # if a values dict is given,
        # the elem must be cloned each time it appears,
        # as there may be different annotations in source
        # elements that are remaining.  if totally
        # removing all annotations, can assume the same
        # slate...
        if values or elem not in cloned:
            newelem = elem._deannotate(values=values, clone=True)
            newelem._copy_internals(clone=clone)
            if not values:
                cloned[elem] = newelem
            return newelem
        else:
            return cloned[elem]

    if element is not None:
        element = clone(element)
    return element


def _shallow_annotate(element, annotations):
    """Annotate the given ClauseElement and copy its internals so that
    internal objects refer to the new annotated object.

    Basically used to apply a "dont traverse" annotation to a
    selectable, without digging throughout the whole
    structure wasting time.
    """
    element = element._annotate(annotations)
    element._copy_internals()
    return element


def _new_annotation_type(cls, base_cls):
    if issubclass(cls, Annotated):
        return cls
    elif cls in annotated_classes:
        return annotated_classes[cls]

    for super_ in cls.__mro__:
        # check if an Annotated subclass more specific than
        # the given base_cls is already registered, such
        # as AnnotatedColumnElement.
        if super_ in annotated_classes:
            base_cls = annotated_classes[super_]
            break

    annotated_classes[cls] = anno_cls = type(
        "Annotated%s" % cls.__name__,
        (base_cls, cls), {})
    globals()["Annotated%s" % cls.__name__] = anno_cls
    return anno_cls


def _prepare_annotations(target_hierarchy, base_cls):
    stack = [target_hierarchy]
    while stack:
        cls = stack.pop()
        stack.extend(cls.__subclasses__())

        _new_annotation_type(cls, base_cls)