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# ext/declarative/base.py
# Copyright (C) 2005-2021 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
"""Internal implementation for declarative."""
import collections
import weakref
from sqlalchemy.orm import instrumentation
from . import clsregistry
from ... import event
from ... import exc
from ... import util
from ...orm import class_mapper
from ...orm import exc as orm_exc
from ...orm import mapper
from ...orm import mapperlib
from ...orm import synonym
from ...orm.attributes import QueryableAttribute
from ...orm.base import _is_mapped_class
from ...orm.base import InspectionAttr
from ...orm.interfaces import MapperProperty
from ...orm.properties import ColumnProperty
from ...orm.properties import CompositeProperty
from ...schema import Column
from ...schema import Table
from ...sql import expression
from ...util import topological
declared_attr = declarative_props = None
def _declared_mapping_info(cls):
# deferred mapping
if _DeferredMapperConfig.has_cls(cls):
return _DeferredMapperConfig.config_for_cls(cls)
# regular mapping
elif _is_mapped_class(cls):
return class_mapper(cls, configure=False)
else:
return None
def _resolve_for_abstract_or_classical(cls):
if cls is object:
return None
if _get_immediate_cls_attr(cls, "__abstract__", strict=True):
for sup in cls.__bases__:
sup = _resolve_for_abstract_or_classical(sup)
if sup is not None:
return sup
else:
return None
else:
classical = _dive_for_classically_mapped_class(cls)
if classical is not None:
return classical
else:
return cls
def _dive_for_classically_mapped_class(cls):
# support issue #4321
# if we are within a base hierarchy, don't
# search at all for classical mappings
if hasattr(cls, "_decl_class_registry"):
return None
manager = instrumentation.manager_of_class(cls)
if manager is not None:
return cls
else:
for sup in cls.__bases__:
mapper = _dive_for_classically_mapped_class(sup)
if mapper is not None:
return sup
else:
return None
def _get_immediate_cls_attr(cls, attrname, strict=False):
"""return an attribute of the class that is either present directly
on the class, e.g. not on a superclass, or is from a superclass but
this superclass is a non-mapped mixin, that is, not a descendant of
the declarative base and is also not classically mapped.
This is used to detect attributes that indicate something about
a mapped class independently from any mapped classes that it may
inherit from.
"""
if not issubclass(cls, object):
return None
for base in cls.__mro__:
_is_declarative_inherits = hasattr(base, "_decl_class_registry")
_is_classicial_inherits = (
not _is_declarative_inherits
and _dive_for_classically_mapped_class(base) is not None
)
if attrname in base.__dict__ and (
base is cls
or (
(base in cls.__bases__ if strict else True)
and not _is_declarative_inherits
and not _is_classicial_inherits
)
):
return getattr(base, attrname)
else:
return None
def _as_declarative(cls, classname, dict_):
global declared_attr, declarative_props
if declared_attr is None:
from .api import declared_attr
declarative_props = (declared_attr, util.classproperty)
if _get_immediate_cls_attr(cls, "__abstract__", strict=True):
return
_MapperConfig.setup_mapping(cls, classname, dict_)
def _check_declared_props_nocascade(obj, name, cls):
if isinstance(obj, declarative_props):
if getattr(obj, "_cascading", False):
util.warn(
"@declared_attr.cascading is not supported on the %s "
"attribute on class %s. This attribute invokes for "
"subclasses in any case." % (name, cls)
)
return True
else:
return False
class _MapperConfig(object):
@classmethod
def setup_mapping(cls, cls_, classname, dict_):
defer_map = _get_immediate_cls_attr(
cls_, "_sa_decl_prepare_nocascade", strict=True
) or hasattr(cls_, "_sa_decl_prepare")
if defer_map:
cfg_cls = _DeferredMapperConfig
else:
cfg_cls = _MapperConfig
cfg_cls(cls_, classname, dict_)
def __init__(self, cls_, classname, dict_):
self.cls = cls_
# dict_ will be a dictproxy, which we can't write to, and we need to!
self.dict_ = dict(dict_)
self.classname = classname
self.persist_selectable = None
self.properties = util.OrderedDict()
self.declared_columns = set()
self.column_copies = {}
self._setup_declared_events()
# temporary registry. While early 1.0 versions
# set up the ClassManager here, by API contract
# we can't do that until there's a mapper.
self.cls._sa_declared_attr_reg = {}
self._scan_attributes()
mapperlib._CONFIGURE_MUTEX.acquire()
try:
clsregistry.add_class(self.classname, self.cls)
self._extract_mappable_attributes()
self._extract_declared_columns()
self._setup_table()
self._setup_inheritance()
self._early_mapping()
finally:
mapperlib._CONFIGURE_MUTEX.release()
def _early_mapping(self):
self.map()
def _setup_declared_events(self):
if _get_immediate_cls_attr(self.cls, "__declare_last__"):
@event.listens_for(mapper, "after_configured")
def after_configured():
self.cls.__declare_last__()
if _get_immediate_cls_attr(self.cls, "__declare_first__"):
@event.listens_for(mapper, "before_configured")
def before_configured():
self.cls.__declare_first__()
def _scan_attributes(self):
cls = self.cls
dict_ = self.dict_
column_copies = self.column_copies
mapper_args_fn = None
table_args = inherited_table_args = None
tablename = None
for base in cls.__mro__:
class_mapped = (
base is not cls
and _declared_mapping_info(base) is not None
and not _get_immediate_cls_attr(
base, "_sa_decl_prepare_nocascade", strict=True
)
)
if not class_mapped and base is not cls:
self._produce_column_copies(base)
for name, obj in vars(base).items():
if name == "__mapper_args__":
check_decl = _check_declared_props_nocascade(
obj, name, cls
)
if not mapper_args_fn and (not class_mapped or check_decl):
# don't even invoke __mapper_args__ until
# after we've determined everything about the
# mapped table.
# make a copy of it so a class-level dictionary
# is not overwritten when we update column-based
# arguments.
def mapper_args_fn():
return dict(cls.__mapper_args__)
elif name == "__tablename__":
check_decl = _check_declared_props_nocascade(
obj, name, cls
)
if not tablename and (not class_mapped or check_decl):
tablename = cls.__tablename__
elif name == "__table_args__":
check_decl = _check_declared_props_nocascade(
obj, name, cls
)
if not table_args and (not class_mapped or check_decl):
table_args = cls.__table_args__
if not isinstance(
table_args, (tuple, dict, type(None))
):
raise exc.ArgumentError(
"__table_args__ value must be a tuple, "
"dict, or None"
)
if base is not cls:
inherited_table_args = True
elif class_mapped:
if isinstance(obj, declarative_props):
util.warn(
"Regular (i.e. not __special__) "
"attribute '%s.%s' uses @declared_attr, "
"but owning class %s is mapped - "
"not applying to subclass %s."
% (base.__name__, name, base, cls)
)
continue
elif base is not cls:
# we're a mixin, abstract base, or something that is
# acting like that for now.
if isinstance(obj, Column):
# already copied columns to the mapped class.
continue
elif isinstance(obj, MapperProperty):
raise exc.InvalidRequestError(
"Mapper properties (i.e. deferred,"
"column_property(), relationship(), etc.) must "
"be declared as @declared_attr callables "
"on declarative mixin classes."
)
elif isinstance(obj, declarative_props):
oldclassprop = isinstance(obj, util.classproperty)
if not oldclassprop and obj._cascading:
if name in dict_:
# unfortunately, while we can use the user-
# defined attribute here to allow a clean
# override, if there's another
# subclass below then it still tries to use
# this. not sure if there is enough
# information here to add this as a feature
# later on.
util.warn(
"Attribute '%s' on class %s cannot be "
"processed due to "
"@declared_attr.cascading; "
"skipping" % (name, cls)
)
dict_[name] = column_copies[
obj
] = ret = obj.__get__(obj, cls)
setattr(cls, name, ret)
else:
if oldclassprop:
util.warn_deprecated(
"Use of sqlalchemy.util.classproperty on "
"declarative classes is deprecated."
)
# access attribute using normal class access
ret = getattr(cls, name)
# correct for proxies created from hybrid_property
# or similar. note there is no known case that
# produces nested proxies, so we are only
# looking one level deep right now.
if (
isinstance(ret, InspectionAttr)
and ret._is_internal_proxy
and not isinstance(
ret.original_property, MapperProperty
)
):
ret = ret.descriptor
dict_[name] = column_copies[obj] = ret
if (
isinstance(ret, (Column, MapperProperty))
and ret.doc is None
):
ret.doc = obj.__doc__
# here, the attribute is some other kind of property that
# we assume is not part of the declarative mapping.
# however, check for some more common mistakes
else:
self._warn_for_decl_attributes(base, name, obj)
if inherited_table_args and not tablename:
table_args = None
self.table_args = table_args
self.tablename = tablename
self.mapper_args_fn = mapper_args_fn
def _warn_for_decl_attributes(self, cls, key, c):
if isinstance(c, expression.ColumnClause):
util.warn(
"Attribute '%s' on class %s appears to be a non-schema "
"'sqlalchemy.sql.column()' "
"object; this won't be part of the declarative mapping"
% (key, cls)
)
def _produce_column_copies(self, base):
cls = self.cls
dict_ = self.dict_
column_copies = self.column_copies
# copy mixin columns to the mapped class
for name, obj in vars(base).items():
if isinstance(obj, Column):
if getattr(cls, name) is not obj:
# if column has been overridden
# (like by the InstrumentedAttribute of the
# superclass), skip
continue
elif obj.foreign_keys:
raise exc.InvalidRequestError(
"Columns with foreign keys to other columns "
"must be declared as @declared_attr callables "
"on declarative mixin classes. "
)
elif name not in dict_ and not (
"__table__" in dict_
and (obj.name or name) in dict_["__table__"].c
):
column_copies[obj] = copy_ = obj.copy()
copy_._creation_order = obj._creation_order
setattr(cls, name, copy_)
dict_[name] = copy_
def _extract_mappable_attributes(self):
cls = self.cls
dict_ = self.dict_
our_stuff = self.properties
late_mapped = _get_immediate_cls_attr(
cls, "_sa_decl_prepare_nocascade", strict=True
)
for k in list(dict_):
if k in ("__table__", "__tablename__", "__mapper_args__"):
continue
value = dict_[k]
if isinstance(value, declarative_props):
if isinstance(value, declared_attr) and value._cascading:
util.warn(
"Use of @declared_attr.cascading only applies to "
"Declarative 'mixin' and 'abstract' classes. "
"Currently, this flag is ignored on mapped class "
"%s" % self.cls
)
value = getattr(cls, k)
elif (
isinstance(value, QueryableAttribute)
and value.class_ is not cls
and value.key != k
):
# detect a QueryableAttribute that's already mapped being
# assigned elsewhere in userland, turn into a synonym()
value = synonym(value.key)
setattr(cls, k, value)
if (
isinstance(value, tuple)
and len(value) == 1
and isinstance(value[0], (Column, MapperProperty))
):
util.warn(
"Ignoring declarative-like tuple value of attribute "
"'%s': possibly a copy-and-paste error with a comma "
"accidentally placed at the end of the line?" % k
)
continue
elif not isinstance(value, (Column, MapperProperty)):
# using @declared_attr for some object that
# isn't Column/MapperProperty; remove from the dict_
# and place the evaluated value onto the class.
if not k.startswith("__"):
dict_.pop(k)
self._warn_for_decl_attributes(cls, k, value)
if not late_mapped:
setattr(cls, k, value)
continue
# we expect to see the name 'metadata' in some valid cases;
# however at this point we see it's assigned to something trying
# to be mapped, so raise for that.
elif k == "metadata":
raise exc.InvalidRequestError(
"Attribute name 'metadata' is reserved "
"for the MetaData instance when using a "
"declarative base class."
)
prop = clsregistry._deferred_relationship(cls, value)
our_stuff[k] = prop
def _extract_declared_columns(self):
our_stuff = self.properties
# set up attributes in the order they were created
our_stuff.sort(key=lambda key: our_stuff[key]._creation_order)
# extract columns from the class dict
declared_columns = self.declared_columns
name_to_prop_key = collections.defaultdict(set)
for key, c in list(our_stuff.items()):
if isinstance(c, (ColumnProperty, CompositeProperty)):
for col in c.columns:
if isinstance(col, Column) and col.table is None:
_undefer_column_name(key, col)
if not isinstance(c, CompositeProperty):
name_to_prop_key[col.name].add(key)
declared_columns.add(col)
elif isinstance(c, Column):
_undefer_column_name(key, c)
name_to_prop_key[c.name].add(key)
declared_columns.add(c)
# if the column is the same name as the key,
# remove it from the explicit properties dict.
# the normal rules for assigning column-based properties
# will take over, including precedence of columns
# in multi-column ColumnProperties.
if key == c.key:
del our_stuff[key]
for name, keys in name_to_prop_key.items():
if len(keys) > 1:
util.warn(
"On class %r, Column object %r named "
"directly multiple times, "
"only one will be used: %s. "
"Consider using orm.synonym instead"
% (self.classname, name, (", ".join(sorted(keys))))
)
def _setup_table(self):
cls = self.cls
tablename = self.tablename
table_args = self.table_args
dict_ = self.dict_
declared_columns = self.declared_columns
declared_columns = self.declared_columns = sorted(
declared_columns, key=lambda c: c._creation_order
)
table = None
if hasattr(cls, "__table_cls__"):
table_cls = util.unbound_method_to_callable(cls.__table_cls__)
else:
table_cls = Table
if "__table__" not in dict_:
if tablename is not None:
args, table_kw = (), {}
if table_args:
if isinstance(table_args, dict):
table_kw = table_args
elif isinstance(table_args, tuple):
if isinstance(table_args[-1], dict):
args, table_kw = table_args[0:-1], table_args[-1]
else:
args = table_args
autoload = dict_.get("__autoload__")
if autoload:
table_kw["autoload"] = True
cls.__table__ = table = table_cls(
tablename,
cls.metadata,
*(tuple(declared_columns) + tuple(args)),
**table_kw
)
else:
table = cls.__table__
if declared_columns:
for c in declared_columns:
if not table.c.contains_column(c):
raise exc.ArgumentError(
"Can't add additional column %r when "
"specifying __table__" % c.key
)
self.local_table = table
def _setup_inheritance(self):
table = self.local_table
cls = self.cls
table_args = self.table_args
declared_columns = self.declared_columns
# since we search for classical mappings now, search for
# multiple mapped bases as well and raise an error.
inherits = []
for c in cls.__bases__:
c = _resolve_for_abstract_or_classical(c)
if c is None:
continue
if _declared_mapping_info(
c
) is not None and not _get_immediate_cls_attr(
c, "_sa_decl_prepare_nocascade", strict=True
):
inherits.append(c)
if inherits:
if len(inherits) > 1:
raise exc.InvalidRequestError(
"Class %s has multiple mapped bases: %r" % (cls, inherits)
)
self.inherits = inherits[0]
else:
self.inherits = None
if (
table is None
and self.inherits is None
and not _get_immediate_cls_attr(cls, "__no_table__")
):
raise exc.InvalidRequestError(
"Class %r does not have a __table__ or __tablename__ "
"specified and does not inherit from an existing "
"table-mapped class." % cls
)
elif self.inherits:
inherited_mapper = _declared_mapping_info(self.inherits)
inherited_table = inherited_mapper.local_table
inherited_persist_selectable = inherited_mapper.persist_selectable
if table is None:
# single table inheritance.
# ensure no table args
if table_args:
raise exc.ArgumentError(
"Can't place __table_args__ on an inherited class "
"with no table."
)
# add any columns declared here to the inherited table.
for c in declared_columns:
if c.name in inherited_table.c:
if inherited_table.c[c.name] is c:
continue
raise exc.ArgumentError(
"Column '%s' on class %s conflicts with "
"existing column '%s'"
% (c, cls, inherited_table.c[c.name])
)
if c.primary_key:
raise exc.ArgumentError(
"Can't place primary key columns on an inherited "
"class with no table."
)
inherited_table.append_column(c)
if (
inherited_persist_selectable is not None
and inherited_persist_selectable is not inherited_table
):
inherited_persist_selectable._refresh_for_new_column(c)
def _prepare_mapper_arguments(self):
properties = self.properties
if self.mapper_args_fn:
mapper_args = self.mapper_args_fn()
else:
mapper_args = {}
# make sure that column copies are used rather
# than the original columns from any mixins
for k in ("version_id_col", "polymorphic_on"):
if k in mapper_args:
v = mapper_args[k]
mapper_args[k] = self.column_copies.get(v, v)
assert (
"inherits" not in mapper_args
), "Can't specify 'inherits' explicitly with declarative mappings"
if self.inherits:
mapper_args["inherits"] = self.inherits
if self.inherits and not mapper_args.get("concrete", False):
# single or joined inheritance
# exclude any cols on the inherited table which are
# not mapped on the parent class, to avoid
# mapping columns specific to sibling/nephew classes
inherited_mapper = _declared_mapping_info(self.inherits)
inherited_table = inherited_mapper.local_table
if "exclude_properties" not in mapper_args:
mapper_args["exclude_properties"] = exclude_properties = set(
[
c.key
for c in inherited_table.c
if c not in inherited_mapper._columntoproperty
]
).union(inherited_mapper.exclude_properties or ())
exclude_properties.difference_update(
[c.key for c in self.declared_columns]
)
# look through columns in the current mapper that
# are keyed to a propname different than the colname
# (if names were the same, we'd have popped it out above,
# in which case the mapper makes this combination).
# See if the superclass has a similar column property.
# If so, join them together.
for k, col in list(properties.items()):
if not isinstance(col, expression.ColumnElement):
continue
if k in inherited_mapper._props:
p = inherited_mapper._props[k]
if isinstance(p, ColumnProperty):
# note here we place the subclass column
# first. See [ticket:1892] for background.
properties[k] = [col] + p.columns
result_mapper_args = mapper_args.copy()
result_mapper_args["properties"] = properties
self.mapper_args = result_mapper_args
def map(self):
self._prepare_mapper_arguments()
if hasattr(self.cls, "__mapper_cls__"):
mapper_cls = util.unbound_method_to_callable(
self.cls.__mapper_cls__
)
else:
mapper_cls = mapper
self.cls.__mapper__ = mp_ = mapper_cls(
self.cls, self.local_table, **self.mapper_args
)
del self.cls._sa_declared_attr_reg
return mp_
class _DeferredMapperConfig(_MapperConfig):
_configs = util.OrderedDict()
def _early_mapping(self):
pass
@property
def cls(self):
return self._cls()
@cls.setter
def cls(self, class_):
self._cls = weakref.ref(class_, self._remove_config_cls)
self._configs[self._cls] = self
@classmethod
def _remove_config_cls(cls, ref):
cls._configs.pop(ref, None)
@classmethod
def has_cls(cls, class_):
# 2.6 fails on weakref if class_ is an old style class
return isinstance(class_, type) and weakref.ref(class_) in cls._configs
@classmethod
def raise_unmapped_for_cls(cls, class_):
if hasattr(class_, "_sa_raise_deferred_config"):
class_._sa_raise_deferred_config()
raise orm_exc.UnmappedClassError(
class_,
msg="Class %s has a deferred mapping on it. It is not yet "
"usable as a mapped class." % orm_exc._safe_cls_name(class_),
)
@classmethod
def config_for_cls(cls, class_):
return cls._configs[weakref.ref(class_)]
@classmethod
def classes_for_base(cls, base_cls, sort=True):
classes_for_base = [
m
for m, cls_ in [(m, m.cls) for m in cls._configs.values()]
if cls_ is not None and issubclass(cls_, base_cls)
]
if not sort:
return classes_for_base
all_m_by_cls = dict((m.cls, m) for m in classes_for_base)
tuples = []
for m_cls in all_m_by_cls:
tuples.extend(
(all_m_by_cls[base_cls], all_m_by_cls[m_cls])
for base_cls in m_cls.__bases__
if base_cls in all_m_by_cls
)
return list(topological.sort(tuples, classes_for_base))
def map(self):
self._configs.pop(self._cls, None)
return super(_DeferredMapperConfig, self).map()
def _add_attribute(cls, key, value):
"""add an attribute to an existing declarative class.
This runs through the logic to determine MapperProperty,
adds it to the Mapper, adds a column to the mapped Table, etc.
"""
if "__mapper__" in cls.__dict__:
if isinstance(value, Column):
_undefer_column_name(key, value)
cls.__table__.append_column(value)
cls.__mapper__.add_property(key, value)
elif isinstance(value, ColumnProperty):
for col in value.columns:
if isinstance(col, Column) and col.table is None:
_undefer_column_name(key, col)
cls.__table__.append_column(col)
cls.__mapper__.add_property(key, value)
elif isinstance(value, MapperProperty):
cls.__mapper__.add_property(
key, clsregistry._deferred_relationship(cls, value)
)
elif isinstance(value, QueryableAttribute) and value.key != key:
# detect a QueryableAttribute that's already mapped being
# assigned elsewhere in userland, turn into a synonym()
value = synonym(value.key)
cls.__mapper__.add_property(
key, clsregistry._deferred_relationship(cls, value)
)
else:
type.__setattr__(cls, key, value)
cls.__mapper__._expire_memoizations()
else:
type.__setattr__(cls, key, value)
def _del_attribute(cls, key):
if (
"__mapper__" in cls.__dict__
and key in cls.__dict__
and not cls.__mapper__._dispose_called
):
value = cls.__dict__[key]
if isinstance(
value, (Column, ColumnProperty, MapperProperty, QueryableAttribute)
):
raise NotImplementedError(
"Can't un-map individual mapped attributes on a mapped class."
)
else:
type.__delattr__(cls, key)
cls.__mapper__._expire_memoizations()
else:
type.__delattr__(cls, key)
def _declarative_constructor(self, **kwargs):
"""A simple constructor that allows initialization from kwargs.
Sets attributes on the constructed instance using the names and
values in ``kwargs``.
Only keys that are present as
attributes of the instance's class are allowed. These could be,
for example, any mapped columns or relationships.
"""
cls_ = type(self)
for k in kwargs:
if not hasattr(cls_, k):
raise TypeError(
"%r is an invalid keyword argument for %s" % (k, cls_.__name__)
)
setattr(self, k, kwargs[k])
_declarative_constructor.__name__ = "__init__"
def _undefer_column_name(key, column):
if column.key is None:
column.key = key
if column.name is None:
column.name = key