mercurial/namespaces.py

namespaces: add bookmarks to the names data structure

This marks the first use of abstracting our different types of named objects
(bookmarks, tags, branches, etc.) and upcoming patches will use this to
simplify logic.

from mercurial import util
import weakref

def tolist(val):
    """
    a convenience method to return an empty list instead of None
    """
    if val is None:
        return []
    else:
        return [val]

class namespaces(object):
    """
    provides an interface to register a generic many-to-many mapping between
    some (namespaced) names and nodes. The goal here is to control the
    pollution of jamming things into tags or bookmarks (in extension-land) and
    to simplify internal bits of mercurial: log output, tab completion, etc.

    More precisely, we define a list of names (the namespace) and  a mapping of
    names to nodes. This name mapping returns a list of nodes.

    Furthermore, each name mapping will be passed a name to lookup which might
    not be in its domain. In this case, each method should return an empty list
    and not raise an error.

    We'll have a dictionary '_names' where each key is a namespace and
    its value is a dictionary of functions:
      'namemap': function that takes a name and returns a list of nodes
    """

    _names_version = 0

    def __init__(self, repo):
        self._names = util.sortdict()
        self._repo = weakref.ref(repo)

        # we need current mercurial named objects (bookmarks, tags, and
        # branches) to be initialized somewhere, so that place is here
        self.addnamespace("bookmarks",
                          lambda repo, name: tolist(repo._bookmarks.get(name)))

    @property
    def repo(self):
        return self._repo()

    def addnamespace(self, namespace, namemap, order=None):
        """
        register a namespace

        namespace: the name to be registered (in plural form)
        namemap: function that inputs a node, output name(s)
        order: optional argument to specify the order of namespaces
               (e.g. 'branches' should be listed before 'bookmarks')
        """
        val = {'namemap': namemap}
        if order is not None:
            self._names.insert(order, namespace, val)
        else:
            self._names[namespace] = val