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Filename : legacy.py
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# event/legacy.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

"""Routines to handle adaption of legacy call signatures,
generation of deprecation notes and docstrings.

"""

from .. import util


def _legacy_signature(since, argnames, converter=None):
    def leg(fn):
        if not hasattr(fn, "_legacy_signatures"):
            fn._legacy_signatures = []
        fn._legacy_signatures.append((since, argnames, converter))
        return fn

    return leg


def _wrap_fn_for_legacy(dispatch_collection, fn, argspec):
    for since, argnames, conv in dispatch_collection.legacy_signatures:
        if argnames[-1] == "**kw":
            has_kw = True
            argnames = argnames[0:-1]
        else:
            has_kw = False

        if len(argnames) == len(argspec.args) and has_kw is bool(
            argspec.varkw
        ):

            if conv:
                assert not has_kw

                def wrap_leg(*args):
                    return fn(*conv(*args))

            else:

                def wrap_leg(*args, **kw):
                    argdict = dict(zip(dispatch_collection.arg_names, args))
                    args = [argdict[name] for name in argnames]
                    if has_kw:
                        return fn(*args, **kw)
                    else:
                        return fn(*args)

            return wrap_leg
    else:
        return fn


def _indent(text, indent):
    return "\n".join(indent + line for line in text.split("\n"))


def _standard_listen_example(dispatch_collection, sample_target, fn):
    example_kw_arg = _indent(
        "\n".join(
            "%(arg)s = kw['%(arg)s']" % {"arg": arg}
            for arg in dispatch_collection.arg_names[0:2]
        ),
        "    ",
    )
    if dispatch_collection.legacy_signatures:
        current_since = max(
            since
            for since, args, conv in dispatch_collection.legacy_signatures
        )
    else:
        current_since = None
    text = (
        "from sqlalchemy import event\n\n"
        "# standard decorator style%(current_since)s\n"
        "@event.listens_for(%(sample_target)s, '%(event_name)s')\n"
        "def receive_%(event_name)s("
        "%(named_event_arguments)s%(has_kw_arguments)s):\n"
        "    \"listen for the '%(event_name)s' event\"\n"
        "\n    # ... (event handling logic) ...\n"
    )

    if len(dispatch_collection.arg_names) > 3:
        text += (
            "\n# named argument style (new in 0.9)\n"
            "@event.listens_for("
            "%(sample_target)s, '%(event_name)s', named=True)\n"
            "def receive_%(event_name)s(**kw):\n"
            "    \"listen for the '%(event_name)s' event\"\n"
            "%(example_kw_arg)s\n"
            "\n    # ... (event handling logic) ...\n"
        )

    text %= {
        "current_since": " (arguments as of %s)" % current_since
        if current_since
        else "",
        "event_name": fn.__name__,
        "has_kw_arguments": ", **kw" if dispatch_collection.has_kw else "",
        "named_event_arguments": ", ".join(dispatch_collection.arg_names),
        "example_kw_arg": example_kw_arg,
        "sample_target": sample_target,
    }
    return text


def _legacy_listen_examples(dispatch_collection, sample_target, fn):
    text = ""
    for since, args, conv in dispatch_collection.legacy_signatures:
        text += (
            "\n# DEPRECATED calling style (pre-%(since)s, "
            "will be removed in a future release)\n"
            "@event.listens_for(%(sample_target)s, '%(event_name)s')\n"
            "def receive_%(event_name)s("
            "%(named_event_arguments)s%(has_kw_arguments)s):\n"
            "    \"listen for the '%(event_name)s' event\"\n"
            "\n    # ... (event handling logic) ...\n"
            % {
                "since": since,
                "event_name": fn.__name__,
                "has_kw_arguments": " **kw"
                if dispatch_collection.has_kw
                else "",
                "named_event_arguments": ", ".join(args),
                "sample_target": sample_target,
            }
        )
    return text


def _version_signature_changes(parent_dispatch_cls, dispatch_collection):
    since, args, conv = dispatch_collection.legacy_signatures[0]
    return (
        "\n.. deprecated:: %(since)s\n"
        "    The :class:`.%(clsname)s.%(event_name)s` event now accepts the \n"
        "    arguments ``%(named_event_arguments)s%(has_kw_arguments)s``.\n"
        "    Support for listener functions which accept the previous \n"
        '    argument signature(s) listed above as "deprecated" will be \n'
        "    removed in a future release."
        % {
            "since": since,
            "clsname": parent_dispatch_cls.__name__,
            "event_name": dispatch_collection.name,
            "named_event_arguments": ", ".join(dispatch_collection.arg_names),
            "has_kw_arguments": ", **kw" if dispatch_collection.has_kw else "",
        }
    )


def _augment_fn_docs(dispatch_collection, parent_dispatch_cls, fn):
    header = (
        ".. container:: event_signatures\n\n"
        "     Example argument forms::\n"
        "\n"
    )

    sample_target = getattr(parent_dispatch_cls, "_target_class_doc", "obj")
    text = header + _indent(
        _standard_listen_example(dispatch_collection, sample_target, fn),
        " " * 8,
    )
    if dispatch_collection.legacy_signatures:
        text += _indent(
            _legacy_listen_examples(dispatch_collection, sample_target, fn),
            " " * 8,
        )

        text += _version_signature_changes(
            parent_dispatch_cls, dispatch_collection
        )

    return util.inject_docstring_text(fn.__doc__, text, 1)