# Source code for sqlalchemy.ext.declarative.api

    # ext/declarative/api.py
    # Copyright (C) 2005-2019 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
    """Public API functions and helpers for declarative."""

    import re
    import weakref

    from .base import _add_attribute
    from .base import _as_declarative
    from .base import _declarative_constructor
    from .base import _DeferredMapperConfig
    from .base import _del_attribute
    from .clsregistry import _class_resolver
    from ... import exc
    from ... import inspection
    from ... import util
    from ...orm import attributes
    from ...orm import comparable_property
    from ...orm import exc as orm_exc
    from ...orm import interfaces
    from ...orm import properties
    from ...orm import synonym as _orm_synonym
    from ...orm.base import _inspect_mapped_class
    from ...orm.base import _mapper_or_none
    from ...orm.util import polymorphic_union
    from ...schema import MetaData
    from ...schema import Table
    from ...util import hybridmethod
    from ...util import hybridproperty
    from ...util import OrderedDict

    def instrument_declarative(cls, registry, metadata):
        """Given a class, configure the class declaratively,
        using the given registry, which can be any dictionary, and
        MetaData object.

        """
        if "_decl_class_registry" in cls.__dict__:
            raise exc.InvalidRequestError(
                "Class %r already has been " "instrumented declaratively" % cls
            )
        cls._decl_class_registry = registry
        cls.metadata = metadata
        _as_declarative(cls, cls.__name__, cls.__dict__)

    def has_inherited_table(cls):
        """Given a class, return True if any of the classes it inherits from has a
        mapped table, otherwise return False.

        This is used in declarative mixins to build attributes that behave
        differently for the base class vs. a subclass in an inheritance
        hierarchy.

        .. seealso::

            :ref:`decl_mixin_inheritance`

        """
        for class_ in cls.__mro__[1:]:
            if getattr(class_, "__table__", None) is not None:
                return True
        return False

    class DeclarativeMeta(type):
        def __init__(cls, classname, bases, dict_):
            if "_decl_class_registry" not in cls.__dict__:
                _as_declarative(cls, classname, cls.__dict__)
            type.__init__(cls, classname, bases, dict_)

        def __setattr__(cls, key, value):
            _add_attribute(cls, key, value)

        def __delattr__(cls, key):
            _del_attribute(cls, key)

    def synonym_for(name, map_column=False):
        """Decorator that produces an :func:`.orm.synonym` attribute in conjunction
        with a Python descriptor.

        The function being decorated is passed to :func:`.orm.synonym` as the
        :paramref:`.orm.synonym.descriptor` parameter::

            class MyClass(Base):
                __tablename__ = 'my_table'

                id = Column(Integer, primary_key=True)
                _job_status = Column("job_status", String(50))

                @synonym_for("job_status")
                @property
                def job_status(self):
                    return "Status: %s" % self._job_status

        The :ref:`hybrid properties <mapper_hybrids>` feature of SQLAlchemy
        is typically preferred instead of synonyms, which is a more legacy
        feature.

        .. seealso::

            :ref:`synonyms` - Overview of synonyms

            :func:`.orm.synonym` - the mapper-level function

            :ref:`mapper_hybrids` - The Hybrid Attribute extension provides an
            updated approach to augmenting attribute behavior more flexibly than
            can be achieved with synonyms.

        """

        def decorate(fn):
            return _orm_synonym(name, map_column=map_column, descriptor=fn)

        return decorate

    def comparable_using(comparator_factory):
        """Decorator, allow a Python @property to be used in query criteria.

        This is a  decorator front end to
        :func:`~sqlalchemy.orm.comparable_property` that passes
        through the comparator_factory and the function being decorated::

          @comparable_using(MyComparatorType)
          @property
          def prop(self):
              return 'special sauce'

        The regular ``comparable_property()`` is also usable directly in a
        declarative setting and may be convenient for read/write properties::

          prop = comparable_property(MyComparatorType)

        """

        def decorate(fn):
            return comparable_property(comparator_factory, fn)

        return decorate

    class declared_attr(interfaces._MappedAttribute, property):
        """Mark a class-level method as representing the definition of
        a mapped property or special declarative member name.

        @declared_attr turns the attribute into a scalar-like
        property that can be invoked from the uninstantiated class.
        Declarative treats attributes specifically marked with
        @declared_attr as returning a construct that is specific
        to mapping or declarative table configuration.  The name
        of the attribute is that of what the non-dynamic version
        of the attribute would be.

        @declared_attr is more often than not applicable to mixins,
        to define relationships that are to be applied to different
        implementors of the class::

            class ProvidesUser(object):
                "A mixin that adds a 'user' relationship to classes."

                @declared_attr
                def user(self):
                    return relationship("User")

        It also can be applied to mapped classes, such as to provide
        a "polymorphic" scheme for inheritance::

            class Employee(Base):
                id = Column(Integer, primary_key=True)
                type = Column(String(50), nullable=False)

                @declared_attr
                def __tablename__(cls):
                    return cls.__name__.lower()

                @declared_attr
                def __mapper_args__(cls):
                    if cls.__name__ == 'Employee':
                        return {
                                "polymorphic_on":cls.type,
                                "polymorphic_identity":"Employee"
                        }
                    else:
                        return {"polymorphic_identity":cls.__name__}

        """

        def __init__(self, fget, cascading=False):
            super(declared_attr, self).__init__(fget)
            self.__doc__ = fget.__doc__
            self._cascading = cascading

        def __get__(desc, self, cls):
            reg = cls.__dict__.get("_sa_declared_attr_reg", None)
            if reg is None:
                if (
                    not re.match(r"^__.+__$", desc.fget.__name__)
                    and attributes.manager_of_class(cls) is None
                ):
                    util.warn(
                        "Unmanaged access of declarative attribute %s from "
                        "non-mapped class %s" % (desc.fget.__name__, cls.__name__)
                    )
                return desc.fget(cls)
            elif desc in reg:
                return reg[desc]
            else:
                reg[desc] = obj = desc.fget(cls)
                return obj

        @hybridmethod
        def _stateful(cls, **kw):
            return _stateful_declared_attr(**kw)

        @hybridproperty
        def cascading(cls):
            """Mark a :class:`.declared_attr` as cascading.

            This is a special-use modifier which indicates that a column
            or MapperProperty-based declared attribute should be configured
            distinctly per mapped subclass, within a mapped-inheritance scenario.

            .. warning::

                The :attr:`.declared_attr.cascading` modifier has several
                limitations:

                * The flag **only** applies to the use of :class:`.declared_attr`
                  on declarative mixin classes and ``__abstract__`` classes; it
                  currently has no effect when used on a mapped class directly.

                * The flag **only** applies to normally-named attributes, e.g.
                  not any special underscore attributes such as ``__tablename__``.
                  On these attributes it has **no** effect.

                * The flag currently **does not allow further overrides** down
                  the class hierarchy; if a subclass tries to override the
                  attribute, a warning is emitted and the overridden attribute
                  is skipped.  This is a limitation that it is hoped will be
                  resolved at some point.

            Below, both MyClass as well as MySubClass will have a distinct
            ``id`` Column object established::

                class HasIdMixin(object):
                    @declared_attr.cascading
                    def id(cls):
                        if has_inherited_table(cls):
                            return Column(
                                ForeignKey('myclass.id'), primary_key=True)
                        else:
                            return Column(Integer, primary_key=True)

                class MyClass(HasIdMixin, Base):
                    __tablename__ = 'myclass'
                    # ...

                class MySubClass(MyClass):
                    ""
                    # ...

            The behavior of the above configuration is that ``MySubClass``
            will refer to both its own ``id`` column as well as that of
            ``MyClass`` underneath the attribute named ``some_id``.

            .. seealso::

                :ref:`declarative_inheritance`

                :ref:`mixin_inheritance_columns`

            """
            return cls._stateful(cascading=True)

    class _stateful_declared_attr(declared_attr):
        def __init__(self, **kw):
            self.kw = kw

        def _stateful(self, **kw):
            new_kw = self.kw.copy()
            new_kw.update(kw)
            return _stateful_declared_attr(**new_kw)

        def __call__(self, fn):
            return declared_attr(fn, **self.kw)

    def declarative_base(
        bind=None,
        metadata=None,
        mapper=None,
        cls=object,
        name="Base",
        constructor=_declarative_constructor,
        class_registry=None,
        metaclass=DeclarativeMeta,
    ):
        r"""Construct a base class for declarative class definitions.

        The new base class will be given a metaclass that produces
        appropriate :class:`~sqlalchemy.schema.Table` objects and makes
        the appropriate :func:`~sqlalchemy.orm.mapper` calls based on the
        information provided declaratively in the class and any subclasses
        of the class.

        :param bind: An optional
          :class:`~sqlalchemy.engine.Connectable`, will be assigned
          the ``bind`` attribute on the :class:`~sqlalchemy.schema.MetaData`
          instance.

        :param metadata:
          An optional :class:`~sqlalchemy.schema.MetaData` instance.  All
          :class:`~sqlalchemy.schema.Table` objects implicitly declared by
          subclasses of the base will share this MetaData.  A MetaData instance
          will be created if none is provided.  The
          :class:`~sqlalchemy.schema.MetaData` instance will be available via the
          `metadata` attribute of the generated declarative base class.

        :param mapper:
          An optional callable, defaults to :func:`~sqlalchemy.orm.mapper`. Will
          be used to map subclasses to their Tables.

        :param cls:
          Defaults to :class:`object`. A type to use as the base for the generated
          declarative base class. May be a class or tuple of classes.

        :param name:
          Defaults to ``Base``.  The display name for the generated
          class.  Customizing this is not required, but can improve clarity in
          tracebacks and debugging.

        :param constructor:
          Defaults to
          :func:`~sqlalchemy.ext.declarative.base._declarative_constructor`, an
          __init__ implementation that assigns \**kwargs for declared
          fields and relationships to an instance.  If ``None`` is supplied,
          no __init__ will be provided and construction will fall back to
          cls.__init__ by way of the normal Python semantics.

        :param class_registry: optional dictionary that will serve as the
          registry of class names-> mapped classes when string names
          are used to identify classes inside of :func:`.relationship`
          and others.  Allows two or more declarative base classes
          to share the same registry of class names for simplified
          inter-base relationships.

        :param metaclass:
          Defaults to :class:`.DeclarativeMeta`.  A metaclass or __metaclass__
          compatible callable to use as the meta type of the generated
          declarative base class.

        .. versionchanged:: 1.1 if :paramref:`.declarative_base.cls` is a
             single class (rather than a tuple), the constructed base class will
             inherit its docstring.

        .. seealso::

            :func:`.as_declarative`

        """
        lcl_metadata = metadata or MetaData()
        if bind:
            lcl_metadata.bind = bind

        if class_registry is None:
            class_registry = weakref.WeakValueDictionary()

        bases = not isinstance(cls, tuple) and (cls,) or cls
        class_dict = dict(
            _decl_class_registry=class_registry, metadata=lcl_metadata
        )

        if isinstance(cls, type):
            class_dict["__doc__"] = cls.__doc__

        if constructor:
            class_dict["__init__"] = constructor
        if mapper:
            class_dict["__mapper_cls__"] = mapper

        return metaclass(name, bases, class_dict)

    def as_declarative(**kw):
        """
        Class decorator for :func:`.declarative_base`.

        Provides a syntactical shortcut to the ``cls`` argument
        sent to :func:`.declarative_base`, allowing the base class
        to be converted in-place to a "declarative" base::

            from sqlalchemy.ext.declarative import as_declarative

            @as_declarative()
            class Base(object):
                @declared_attr
                def __tablename__(cls):
                    return cls.__name__.lower()
                id = Column(Integer, primary_key=True)

            class MyMappedClass(Base):
                # ...

        All keyword arguments passed to :func:`.as_declarative` are passed
        along to :func:`.declarative_base`.

        .. seealso::

            :func:`.declarative_base`

        """

        def decorate(cls):
            kw["cls"] = cls
            kw["name"] = cls.__name__
            return declarative_base(**kw)

        return decorate

    class ConcreteBase(object):
        """A helper class for 'concrete' declarative mappings.

        :class:`.ConcreteBase` will use the :func:`.polymorphic_union`
        function automatically, against all tables mapped as a subclass
        to this class.   The function is called via the
        ``__declare_last__()`` function, which is essentially
        a hook for the :meth:`.after_configured` event.

        :class:`.ConcreteBase` produces a mapped
        table for the class itself.  Compare to :class:`.AbstractConcreteBase`,
        which does not.

        Example::

            from sqlalchemy.ext.declarative import ConcreteBase

            class Employee(ConcreteBase, Base):
                __tablename__ = 'employee'
                employee_id = Column(Integer, primary_key=True)
                name = Column(String(50))
                __mapper_args__ = {
                                'polymorphic_identity':'employee',
                                'concrete':True}

            class Manager(Employee):
                __tablename__ = 'manager'
                employee_id = Column(Integer, primary_key=True)
                name = Column(String(50))
                manager_data = Column(String(40))
                __mapper_args__ = {
                                'polymorphic_identity':'manager',
                                'concrete':True}

        .. seealso::

            :class:`.AbstractConcreteBase`

            :ref:`concrete_inheritance`

            :ref:`inheritance_concrete_helpers`

        """

        @classmethod
        def _create_polymorphic_union(cls, mappers):
            return polymorphic_union(
                OrderedDict(
                    (mp.polymorphic_identity, mp.local_table) for mp in mappers
                ),
                "type",
                "pjoin",
            )

        @classmethod
        def __declare_first__(cls):
            m = cls.__mapper__
            if m.with_polymorphic:
                return

            mappers = list(m.self_and_descendants)
            pjoin = cls._create_polymorphic_union(mappers)
            m._set_with_polymorphic(("*", pjoin))
            m._set_polymorphic_on(pjoin.c.type)

    class AbstractConcreteBase(ConcreteBase):
        """A helper class for 'concrete' declarative mappings.

        :class:`.AbstractConcreteBase` will use the :func:`.polymorphic_union`
        function automatically, against all tables mapped as a subclass
        to this class.   The function is called via the
        ``__declare_last__()`` function, which is essentially
        a hook for the :meth:`.after_configured` event.

        :class:`.AbstractConcreteBase` does produce a mapped class
        for the base class, however it is not persisted to any table; it
        is instead mapped directly to the "polymorphic" selectable directly
        and is only used for selecting.  Compare to :class:`.ConcreteBase`,
        which does create a persisted table for the base class.

        .. note::

            The :class:`.AbstractConcreteBase` class does not intend to set up  the
            mapping for the base class until all the subclasses have been defined,
            as it needs to create a mapping against a selectable that will include
            all subclass tables.  In order to achieve this, it waits for the
            **mapper configuration event** to occur, at which point it scans
            through all the configured subclasses and sets up a mapping that will
            query against all subclasses at once.

            While this event is normally invoked automatically, in the case of
            :class:`.AbstractConcreteBase`, it may be necessary to invoke it
            explicitly after **all** subclass mappings are defined, if the first
            operation is to be a query against this base class.  To do so, invoke
            :func:`.configure_mappers` once all the desired classes have been
            configured::

                from sqlalchemy.orm import configure_mappers

                configure_mappers()

            .. seealso::

                :func:`.orm.configure_mappers`

        Example::

            from sqlalchemy.ext.declarative import AbstractConcreteBase

            class Employee(AbstractConcreteBase, Base):
                pass

            class Manager(Employee):
                __tablename__ = 'manager'
                employee_id = Column(Integer, primary_key=True)
                name = Column(String(50))
                manager_data = Column(String(40))

                __mapper_args__ = {
                    'polymorphic_identity':'manager',
                    'concrete':True}

            configure_mappers()

        The abstract base class is handled by declarative in a special way;
        at class configuration time, it behaves like a declarative mixin
        or an ``__abstract__`` base class.   Once classes are configured
        and mappings are produced, it then gets mapped itself, but
        after all of its descendants.  This is a very unique system of mapping
        not found in any other SQLAlchemy system.

        Using this approach, we can specify columns and properties
        that will take place on mapped subclasses, in the way that
        we normally do as in :ref:`declarative_mixins`::

            class Company(Base):
                __tablename__ = 'company'
                id = Column(Integer, primary_key=True)

            class Employee(AbstractConcreteBase, Base):
                employee_id = Column(Integer, primary_key=True)

                @declared_attr
                def company_id(cls):
                    return Column(ForeignKey('company.id'))

                @declared_attr
                def company(cls):
                    return relationship("Company")

            class Manager(Employee):
                __tablename__ = 'manager'

                name = Column(String(50))
                manager_data = Column(String(40))

                __mapper_args__ = {
                    'polymorphic_identity':'manager',
                    'concrete':True}

            configure_mappers()

        When we make use of our mappings however, both ``Manager`` and
        ``Employee`` will have an independently usable ``.company`` attribute::

            session.query(Employee).filter(Employee.company.has(id=5))

        .. versionchanged:: 1.0.0 - The mechanics of :class:`.AbstractConcreteBase`
           have been reworked to support relationships established directly
           on the abstract base, without any special configurational steps.

        .. seealso::

            :class:`.ConcreteBase`

            :ref:`concrete_inheritance`

            :ref:`inheritance_concrete_helpers`

        """

        __no_table__ = True

        @classmethod
        def __declare_first__(cls):
            cls._sa_decl_prepare_nocascade()

        @classmethod
        def _sa_decl_prepare_nocascade(cls):
            if getattr(cls, "__mapper__", None):
                return

            to_map = _DeferredMapperConfig.config_for_cls(cls)

            # can't rely on 'self_and_descendants' here
            # since technically an immediate subclass
            # might not be mapped, but a subclass
            # may be.
            mappers = []
            stack = list(cls.__subclasses__())
            while stack:
                klass = stack.pop()
                stack.extend(klass.__subclasses__())
                mn = _mapper_or_none(klass)
                if mn is not None:
                    mappers.append(mn)
            pjoin = cls._create_polymorphic_union(mappers)

            # For columns that were declared on the class, these
            # are normally ignored with the "__no_table__" mapping,
            # unless they have a different attribute key vs. col name
            # and are in the properties argument.
            # In that case, ensure we update the properties entry
            # to the correct column from the pjoin target table.
            declared_cols = set(to_map.declared_columns)
            for k, v in list(to_map.properties.items()):
                if v in declared_cols:
                    to_map.properties[k] = pjoin.c[v.key]

            to_map.local_table = pjoin

            m_args = to_map.mapper_args_fn or dict

            def mapper_args():
                args = m_args()
                args["polymorphic_on"] = pjoin.c.type
                return args

            to_map.mapper_args_fn = mapper_args

            m = to_map.map()

            for scls in cls.__subclasses__():
                sm = _mapper_or_none(scls)
                if sm and sm.concrete and cls in scls.__bases__:
                    sm._set_concrete_base(m)

        @classmethod
        def _sa_raise_deferred_config(cls):
            raise orm_exc.UnmappedClassError(
                cls,
                msg="Class %s is a subclass of AbstractConcreteBase and "
                "has a mapping pending until all subclasses are defined. "
                "Call the sqlalchemy.orm.configure_mappers() function after "
                "all subclasses have been defined to "
                "complete the mapping of this class."
                % orm_exc._safe_cls_name(cls),
            )

    class DeferredReflection(object):
        """A helper class for construction of mappings based on
        a deferred reflection step.

        Normally, declarative can be used with reflection by
        setting a :class:`.Table` object using autoload=True
        as the ``__table__`` attribute on a declarative class.
        The caveat is that the :class:`.Table` must be fully
        reflected, or at the very least have a primary key column,
        at the point at which a normal declarative mapping is
        constructed, meaning the :class:`.Engine` must be available
        at class declaration time.

        The :class:`.DeferredReflection` mixin moves the construction
        of mappers to be at a later point, after a specific
        method is called which first reflects all :class:`.Table`
        objects created so far.   Classes can define it as such::

            from sqlalchemy.ext.declarative import declarative_base
            from sqlalchemy.ext.declarative import DeferredReflection
            Base = declarative_base()

            class MyClass(DeferredReflection, Base):
                __tablename__ = 'mytable'

        Above, ``MyClass`` is not yet mapped.   After a series of
        classes have been defined in the above fashion, all tables
        can be reflected and mappings created using
        :meth:`.prepare`::

            engine = create_engine("someengine://...")
            DeferredReflection.prepare(engine)

        The :class:`.DeferredReflection` mixin can be applied to individual
        classes, used as the base for the declarative base itself,
        or used in a custom abstract class.   Using an abstract base
        allows that only a subset of classes to be prepared for a
        particular prepare step, which is necessary for applications
        that use more than one engine.  For example, if an application
        has two engines, you might use two bases, and prepare each
        separately, e.g.::

            class ReflectedOne(DeferredReflection, Base):
                __abstract__ = True

            class ReflectedTwo(DeferredReflection, Base):
                __abstract__ = True

            class MyClass(ReflectedOne):
                __tablename__ = 'mytable'

            class MyOtherClass(ReflectedOne):
                __tablename__ = 'myothertable'

            class YetAnotherClass(ReflectedTwo):
                __tablename__ = 'yetanothertable'

            # ... etc.

        Above, the class hierarchies for ``ReflectedOne`` and
        ``ReflectedTwo`` can be configured separately::

            ReflectedOne.prepare(engine_one)
            ReflectedTwo.prepare(engine_two)

        """

        @classmethod
        def prepare(cls, engine):
            """Reflect all :class:`.Table` objects for all current
            :class:`.DeferredReflection` subclasses"""

            to_map = _DeferredMapperConfig.classes_for_base(cls)
            for thingy in to_map:
                cls._sa_decl_prepare(thingy.local_table, engine)
                thingy.map()
                mapper = thingy.cls.__mapper__
                metadata = mapper.class_.metadata
                for rel in mapper._props.values():
                    if (
                        isinstance(rel, properties.RelationshipProperty)
                        and rel.secondary is not None
                    ):
                        if isinstance(rel.secondary, Table):
                            cls._reflect_table(rel.secondary, engine)
                        elif isinstance(rel.secondary, _class_resolver):
                            rel.secondary._resolvers += (
                                cls._sa_deferred_table_resolver(engine, metadata),
                            )

        @classmethod
        def _sa_deferred_table_resolver(cls, engine, metadata):
            def _resolve(key):
                t1 = Table(key, metadata)
                cls._reflect_table(t1, engine)
                return t1

            return _resolve

        @classmethod
        def _sa_decl_prepare(cls, local_table, engine):
            # autoload Table, which is already
            # present in the metadata.  This
            # will fill in db-loaded columns
            # into the existing Table object.
            if local_table is not None:
                cls._reflect_table(local_table, engine)

        @classmethod
        def _sa_raise_deferred_config(cls):
            raise orm_exc.UnmappedClassError(
                cls,
                msg="Class %s is a subclass of DeferredReflection.  "
                "Mappings are not produced until the .prepare() "
                "method is called on the class hierarchy."
                % orm_exc._safe_cls_name(cls),
            )

        @classmethod
        def _reflect_table(cls, table, engine):
            Table(
                table.name,
                table.metadata,
                extend_existing=True,
                autoload_replace=False,
                autoload=True,
                autoload_with=engine,
                schema=table.schema,
            )

    @inspection._inspects(DeclarativeMeta)
    def _inspect_decl_meta(cls):
        mp = _inspect_mapped_class(cls)
        if mp is None:
            if _DeferredMapperConfig.has_cls(cls):
                _DeferredMapperConfig.raise_unmapped_for_cls(cls)
                raise orm_exc.UnmappedClassError(
                    cls,
                    msg="Class %s has a deferred mapping on it.  It is not yet "
                    "usable as a mapped class." % orm_exc._safe_cls_name(cls),
                )
        return mp