view mercurial/utils/repoviewutil.py @ 51725:bbe59cc5d2e1

rust-changelog: accessing the index

The `Index` object is currently the one providing all DAG related
algorithms, starting with simple ancestors iteration up to more
advanced ones (ranges, common ancestors…).

From pure Rust code, there was no way to access the changelog index for
a given `Repository`, probably because `rhg` does not use any such algorithm
yet.

# repoviewutil.py - constaints data relevant to repoview.py and other module
#
# Copyright 2012 Pierre-Yves David <[e-mail]>
#                Logilab SA        <[e-mail]>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

from .. import error

### Nearest subset relation
# Nearest subset of filter X is a filter Y so that:
# * Y is included in X,
# * X - Y is as small as possible.
# This create and ordering used for branchmap purpose.
# the ordering may be partial
subsettable = {
    None: b'visible',
    b'visible-hidden': b'visible',
    b'visible': b'served',
    b'served.hidden': b'served',
    b'served': b'immutable',
    b'immutable': b'base',
}


def get_ordered_subset():
    """return a list of subset name from dependencies to dependents"""
    _unfinalized = set(subsettable.values())
    ordered = []

    # the subset table is expected to be small so we do the stupid N² version
    # of the algorithm
    while _unfinalized:
        this_level = []
        for candidate in _unfinalized:
            dependency = subsettable.get(candidate)
            if dependency not in _unfinalized:
                this_level.append(candidate)

        if not this_level:
            msg = "cyclic dependencies in repoview subset %r"
            msg %= subsettable
            raise error.ProgrammingError(msg)

        this_level.sort(key=lambda x: x if x is not None else '')

        ordered.extend(this_level)
        _unfinalized.difference_update(this_level)

    return ordered