kallithea Files · rhodecode/lib/dbmigrate/migrate/versioning/util/keyedinstance.py

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Zachary Auclair

Allowing multiple issue servers to be autolinked in the changeset view;
linking is now contingent on issue_server_link, issue_pat and issue_prefix
being defined; multiple servers can be used by specifying a common suffix on all
the above variables, ie ..

issue_server_link_1
issue_pat_1
issue_prefix_1

.. and ..

issue_server_link_other
issue_pat_other
issue_prefix_other

.. would be treated as two distinct servers, but ..

issue_pat_thing

.. would be ignored (since the other two requisite vars aren't present).

This patch is backwards compatible with existing variables (as a suffix
isn't needed).

#!/usr/bin/env python
# -*- coding: utf-8 -*-

class KeyedInstance(object):
    """A class whose instances have a unique identifier of some sort
    No two instances with the same unique ID should exist - if we try to create
    a second instance, the first should be returned.
    """

    _instances = dict()

    def __new__(cls, *p, **k):
        instances = cls._instances
        clskey = str(cls)
        if clskey not in instances:
            instances[clskey] = dict()
        instances = instances[clskey]

        key = cls._key(*p, **k)
        if key not in instances:
            instances[key] = super(KeyedInstance, cls).__new__(cls)
        return instances[key]

    @classmethod
    def _key(cls, *p, **k):
        """Given a unique identifier, return a dictionary key
        This should be overridden by child classes, to specify which parameters
        should determine an object's uniqueness
        """
        raise NotImplementedError()

    @classmethod
    def clear(cls):
        # Allow cls.clear() as well as uniqueInstance.clear(cls)
        if str(cls) in cls._instances:
            del cls._instances[str(cls)]