view hgext3rd/topic/evolvebits.py @ 6935:954d7ea5cd67 stable tip

stack: when stack base is obsolete, pick any successor, even if at random

There are situations when s0 is obsolete and we also cannot pick just one
successor for it to use in stack. In such a case, let's pick the "latest"
successor from the first set.

We're assuming that obsutil.successorssets() returns data in the same order (it
should, since it makes sure to sort data internally). Keeping that in mind,
while the successor picked for s0 by this code is not based on any sort of
sophisticated logic, it should nonetheless be the same every time.

This patch is probably not going to completely break anything that was
previously working fine, because the previous behavior was to just abort with
an exception.

import collections

from mercurial import (
    obsutil,
)

# Copied from evolve 081605c2e9b6

def builddependencies(repo, revs):
    """returns dependency graphs giving an order to solve instability of revs
    (see _orderrevs for more information on usage)"""

    # For each troubled revision we keep track of what instability if any should
    # be resolved in order to resolve it. Example:
    # dependencies = {3: [6], 6:[]}
    # Means that: 6 has no dependency, 3 depends on 6 to be solved
    dependencies = {}
    # rdependencies is the inverted dict of dependencies
    rdependencies = collections.defaultdict(set)

    for r in revs:
        dependencies[r] = set()
        for p in repo[r].parents():
            try:
                succ = _singlesuccessor(repo, p)
            except MultipleSuccessorsError as exc:
                dependencies[r] = exc.successorssets
                continue
            if succ in revs:
                dependencies[r].add(succ)
                rdependencies[succ].add(r)
    return dependencies, rdependencies

def _singlesuccessor(repo, p):
    """returns p (as rev) if not obsolete or its unique latest successors

    fail if there are no such successor"""

    if not p.obsolete():
        return p.rev()
    obs = repo[p]
    ui = repo.ui
    cache = {}
    newer = obsutil.successorssets(repo, obs.node(), cache=cache)
    # search of a parent which is not killed
    while not newer:
        ui.debug(b"stabilize target %s is plain dead,"
                 b" trying to stabilize on its parent\n" %
                 obs)
        obs = obs.p1()
        newer = obsutil.successorssets(repo, obs.node(), cache=cache)
    if 1 < len(newer):
        # divergence case
        # we should pick as arbitrary one
        raise MultipleSuccessorsError(newer)
    elif 1 < len(newer[0]):
        splitheads = list(repo.revs(b'heads(%ln::%ln)', newer[0], newer[0]))
        if 1 < len(splitheads):
            # split case, See if we can make sense of it.
            raise MultipleSuccessorsError(newer)
        return splitheads[0]

    return repo[newer[0][0]].rev()

class MultipleSuccessorsError(RuntimeError):
    """Exception raised by _singlesuccessor when multiple successor sets exists

    The object contains the list of successorssets in its 'successorssets'
    attribute to call to easily recover.
    """

    def __init__(self, successorssets):
        self.successorssets = successorssets