Function _generate_init

lib/sqlalchemy/orm/instrumentation.py:704–745

Build an __init__ decorator that triggers ClassManager events.

(class_, class_manager, original_init)

def _generate_init(class_, class_manager, original_init):
    """Build an __init__ decorator that triggers ClassManager events."""

    # TODO: we should use the ClassManager's notion of the
    # original '__init__' method, once ClassManager is fixed
    # to always reference that.

    if original_init is None:
        original_init = class_.__init__

    # Go through some effort here and don't change the user's __init__
    # calling signature, including the unlikely case that it has
    # a return value.
    # FIXME: need to juggle local names to avoid constructor argument
    # clashes.
    func_body = """\
def __init__(%(apply_pos)s):
    new_state = class_manager._new_state_if_none(%(self_arg)s)
    if new_state:
        return new_state._initialize_instance(%(apply_kw)s)
    else:
        return original_init(%(apply_kw)s)
"""
    func_vars = util.format_argspec_init(original_init, grouped=False)
    func_text = func_body % func_vars

    func_defaults = getattr(original_init, "__defaults__", None)
    func_kw_defaults = getattr(original_init, "__kwdefaults__", None)

    env = locals().copy()
    env["__name__"] = __name__
    exec(func_text, env)
    __init__ = env["__init__"]
    __init__.__doc__ = original_init.__doc__
    __init__._sa_original_init = original_init

    if func_defaults:
        __init__.__defaults__ = func_defaults
    if func_kw_defaults:
        __init__.__kwdefaults__ = func_kw_defaults

    return __init__