94 lines
3.0 KiB
Python
94 lines
3.0 KiB
Python
|
# sqlalchemy/inspect.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
|
||
|
|
|
||
|
|
"""The inspection module provides the :func:`_sa.inspect` function,
|
||
|
|
which delivers runtime information about a wide variety
|
||
|
|
of SQLAlchemy objects, both within the Core as well as the
|
||
|
|
ORM.
|
||
|
|
|
||
|
|
The :func:`_sa.inspect` function is the entry point to SQLAlchemy's
|
||
|
|
public API for viewing the configuration and construction
|
||
|
|
of in-memory objects. Depending on the type of object
|
||
|
|
passed to :func:`_sa.inspect`, the return value will either be
|
||
|
|
a related object which provides a known interface, or in many
|
||
|
|
cases it will return the object itself.
|
||
|
|
|
||
|
|
The rationale for :func:`_sa.inspect` is twofold. One is that
|
||
|
|
it replaces the need to be aware of a large variety of "information
|
||
|
|
getting" functions in SQLAlchemy, such as
|
||
|
|
:meth:`_reflection.Inspector.from_engine` (deprecated in 1.4),
|
||
|
|
:func:`.orm.attributes.instance_state`, :func:`_orm.class_mapper`,
|
||
|
|
and others. The other is that the return value of :func:`_sa.inspect`
|
||
|
|
is guaranteed to obey a documented API, thus allowing third party
|
||
|
|
tools which build on top of SQLAlchemy configurations to be constructed
|
||
|
|
in a forwards-compatible way.
|
||
|
|
|
||
|
|
"""
|
||
|
|
|
||
|
|
from . import exc
|
||
|
|
from . import util
|
||
|
|
|
||
|
|
|
||
|
|
_registrars = util.defaultdict(list)
|
||
|
|
|
||
|
|
|
||
|
|
def inspect(subject, raiseerr=True):
|
||
|
|
"""Produce an inspection object for the given target.
|
||
|
|
|
||
|
|
The returned value in some cases may be the
|
||
|
|
same object as the one given, such as if a
|
||
|
|
:class:`_orm.Mapper` object is passed. In other
|
||
|
|
cases, it will be an instance of the registered
|
||
|
|
inspection type for the given object, such as
|
||
|
|
if an :class:`_engine.Engine` is passed, an
|
||
|
|
:class:`_reflection.Inspector` object is returned.
|
||
|
|
|
||
|
|
:param subject: the subject to be inspected.
|
||
|
|
:param raiseerr: When ``True``, if the given subject
|
||
|
|
does not
|
||
|
|
correspond to a known SQLAlchemy inspected type,
|
||
|
|
:class:`sqlalchemy.exc.NoInspectionAvailable`
|
||
|
|
is raised. If ``False``, ``None`` is returned.
|
||
|
|
|
||
|
|
"""
|
||
|
|
type_ = type(subject)
|
||
|
|
for cls in type_.__mro__:
|
||
|
|
if cls in _registrars:
|
||
|
|
reg = _registrars[cls]
|
||
|
|
if reg is True:
|
||
|
|
return subject
|
||
|
|
ret = reg(subject)
|
||
|
|
if ret is not None:
|
||
|
|
break
|
||
|
|
else:
|
||
|
|
reg = ret = None
|
||
|
|
|
||
|
|
if raiseerr and (reg is None or ret is None):
|
||
|
|
raise exc.NoInspectionAvailable(
|
||
|
|
"No inspection system is "
|
||
|
|
"available for object of type %s" % type_
|
||
|
|
)
|
||
|
|
return ret
|
||
|
|
|
||
|
|
|
||
|
|
def _inspects(*types):
|
||
|
|
def decorate(fn_or_cls):
|
||
|
|
for type_ in types:
|
||
|
|
if type_ in _registrars:
|
||
|
|
raise AssertionError(
|
||
|
|
"Type %s is already " "registered" % type_
|
||
|
|
)
|
||
|
|
_registrars[type_] = fn_or_cls
|
||
|
|
return fn_or_cls
|
||
|
|
|
||
|
|
return decorate
|
||
|
|
|
||
|
|
|
||
|
|
def _self_inspects(cls):
|
||
|
|
_inspects(cls)(True)
|
||
|
|
return cls
|