view mercurial/destutil.py @ 32001:c85f19c66e8d

tests: add tests for poorly behaving HTTP server

I've spent several hours over the past few weeks investigating
networking failures involving hg.mozilla.org. As part of this, it
has become clear that the Mercurial client's error handling when
it encounters network failures is far from robust.

To prove this is true, I've devised a battery of tests simulating
various network failures, notably premature connection closes. To
achieve this, I've implemented an extension that monkeypatches the
built-in HTTP server and hooks in at the socket level and allows
various events to occur based on config options. For example, you
can refuse to accept() a client socket or you can close() the socket
after N bytes have been sent or received. The latter effectively
simulates an unexpected connection drop (and these occur all the
time in the real world).

The new test file launches servers exhibiting various "bad" behaviors
and points a client at them. As the many TODO comments in the test
call attention to, Mercurial often displays unhelpful errors when
network-related failures occur. This makes it difficult for users
to understand what's going on and difficult for server administrators
to pinpoint root causes without packet tracing.

Upcoming patches will attempt to fix these error handling
deficiencies.

# destutil.py - Mercurial utility function for command destination
#
#  Copyright Matt Mackall <[e-mail]> and other
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

from __future__ import absolute_import

from .i18n import _
from . import (
    bookmarks,
    error,
    obsolete,
    scmutil,
)

def _destupdateobs(repo, clean):
    """decide of an update destination from obsolescence markers"""
    node = None
    wc = repo[None]
    p1 = wc.p1()
    movemark = None

    if p1.obsolete() and not p1.children():
        # allow updating to successors
        successors = obsolete.successorssets(repo, p1.node())

        # behavior of certain cases is as follows,
        #
        # divergent changesets: update to highest rev, similar to what
        #     is currently done when there are more than one head
        #     (i.e. 'tip')
        #
        # replaced changesets: same as divergent except we know there
        # is no conflict
        #
        # pruned changeset: no update is done; though, we could
        #     consider updating to the first non-obsolete parent,
        #     similar to what is current done for 'hg prune'

        if successors:
            # flatten the list here handles both divergent (len > 1)
            # and the usual case (len = 1)
            successors = [n for sub in successors for n in sub]

            # get the max revision for the given successors set,
            # i.e. the 'tip' of a set
            node = repo.revs('max(%ln)', successors).first()
            if bookmarks.isactivewdirparent(repo):
                movemark = repo['.'].node()
    return node, movemark, None

def _destupdatebook(repo, clean):
    """decide on an update destination from active bookmark"""
    # we also move the active bookmark, if any
    activemark = None
    node, movemark = bookmarks.calculateupdate(repo.ui, repo, None)
    if node is not None:
        activemark = node
    return node, movemark, activemark

def _destupdatebranch(repo, clean):
    """decide on an update destination from current branch

    This ignores closed branch heads.
    """
    wc = repo[None]
    movemark = node = None
    currentbranch = wc.branch()

    if clean:
        currentbranch = repo['.'].branch()

    if currentbranch in repo.branchmap():
        heads = repo.branchheads(currentbranch)
        if heads:
            node = repo.revs('max(.::(%ln))', heads).first()
        if bookmarks.isactivewdirparent(repo):
            movemark = repo['.'].node()
    elif currentbranch == 'default' and not wc.p1():
        # "null" parent belongs to "default" branch, but it doesn't exist, so
        # update to the tipmost non-closed branch head
        node = repo.revs('max(head() and not closed())').first()
    else:
        node = repo['.'].node()
    return node, movemark, None

def _destupdatebranchfallback(repo, clean):
    """decide on an update destination from closed heads in current branch"""
    wc = repo[None]
    currentbranch = wc.branch()
    movemark = None
    if currentbranch in repo.branchmap():
        # here, all descendant branch heads are closed
        heads = repo.branchheads(currentbranch, closed=True)
        assert heads, "any branch has at least one head"
        node = repo.revs('max(.::(%ln))', heads).first()
        assert node is not None, ("any revision has at least "
                                  "one descendant branch head")
        if bookmarks.isactivewdirparent(repo):
            movemark = repo['.'].node()
    else:
        # here, no "default" branch, and all branches are closed
        node = repo.lookup('tip')
        assert node is not None, "'tip' exists even in empty repository"
    return node, movemark, None

# order in which each step should be evaluated
# steps are run until one finds a destination
destupdatesteps = ['evolution', 'bookmark', 'branch', 'branchfallback']
# mapping to ease extension overriding steps.
destupdatestepmap = {'evolution': _destupdateobs,
                     'bookmark': _destupdatebook,
                     'branch': _destupdatebranch,
                     'branchfallback': _destupdatebranchfallback,
                     }

def destupdate(repo, clean=False):
    """destination for bare update operation

    return (rev, movemark, activemark)

    - rev: the revision to update to,
    - movemark: node to move the active bookmark from
                (cf bookmark.calculate update),
    - activemark: a bookmark to activate at the end of the update.
    """
    node = movemark = activemark = None

    for step in destupdatesteps:
        node, movemark, activemark = destupdatestepmap[step](repo, clean)
        if node is not None:
            break
    rev = repo[node].rev()

    return rev, movemark, activemark

msgdestmerge = {
    # too many matching divergent bookmark
    'toomanybookmarks':
        {'merge':
            (_("multiple matching bookmarks to merge -"
               " please merge with an explicit rev or bookmark"),
             _("run 'hg heads' to see all heads")),
         'rebase':
            (_("multiple matching bookmarks to rebase -"
               " please rebase to an explicit rev or bookmark"),
             _("run 'hg heads' to see all heads")),
        },
    # no other matching divergent bookmark
    'nootherbookmarks':
        {'merge':
            (_("no matching bookmark to merge - "
               "please merge with an explicit rev or bookmark"),
             _("run 'hg heads' to see all heads")),
         'rebase':
            (_("no matching bookmark to rebase - "
               "please rebase to an explicit rev or bookmark"),
             _("run 'hg heads' to see all heads")),
        },
    # branch have too many unbookmarked heads, no obvious destination
    'toomanyheads':
        {'merge':
            (_("branch '%s' has %d heads - please merge with an explicit rev"),
             _("run 'hg heads .' to see heads")),
         'rebase':
            (_("branch '%s' has %d heads - please rebase to an explicit rev"),
             _("run 'hg heads .' to see heads")),
        },
    # branch have no other unbookmarked heads
    'bookmarkedheads':
        {'merge':
            (_("heads are bookmarked - please merge with an explicit rev"),
             _("run 'hg heads' to see all heads")),
         'rebase':
            (_("heads are bookmarked - please rebase to an explicit rev"),
             _("run 'hg heads' to see all heads")),
        },
    # branch have just a single heads, but there is other branches
    'nootherbranchheads':
        {'merge':
            (_("branch '%s' has one head - please merge with an explicit rev"),
             _("run 'hg heads' to see all heads")),
         'rebase':
            (_("branch '%s' has one head - please rebase to an explicit rev"),
             _("run 'hg heads' to see all heads")),
        },
    # repository have a single head
    'nootherheads':
        {'merge':
            (_('nothing to merge'),
            None),
         'rebase':
            (_('nothing to rebase'),
            None),
        },
    # repository have a single head and we are not on it
    'nootherheadsbehind':
        {'merge':
            (_('nothing to merge'),
             _("use 'hg update' instead")),
         'rebase':
            (_('nothing to rebase'),
             _("use 'hg update' instead")),
        },
    # We are not on a head
    'notatheads':
        {'merge':
            (_('working directory not at a head revision'),
             _("use 'hg update' or merge with an explicit revision")),
         'rebase':
            (_('working directory not at a head revision'),
             _("use 'hg update' or rebase to an explicit revision"))
        },
    'emptysourceset':
        {'merge':
            (_('source set is empty'),
             None),
         'rebase':
            (_('source set is empty'),
             None),
        },
    'multiplebranchessourceset':
        {'merge':
            (_('source set is rooted in multiple branches'),
             None),
         'rebase':
            (_('rebaseset is rooted in multiple named branches'),
             _('specify an explicit destination with --dest')),
        },
    }

def _destmergebook(repo, action='merge', sourceset=None, destspace=None):
    """find merge destination in the active bookmark case"""
    node = None
    bmheads = repo.bookmarkheads(repo._activebookmark)
    curhead = repo[repo._activebookmark].node()
    if len(bmheads) == 2:
        if curhead == bmheads[0]:
            node = bmheads[1]
        else:
            node = bmheads[0]
    elif len(bmheads) > 2:
        msg, hint = msgdestmerge['toomanybookmarks'][action]
        raise error.ManyMergeDestAbort(msg, hint=hint)
    elif len(bmheads) <= 1:
        msg, hint = msgdestmerge['nootherbookmarks'][action]
        raise error.NoMergeDestAbort(msg, hint=hint)
    assert node is not None
    return node

def _destmergebranch(repo, action='merge', sourceset=None, onheadcheck=True,
                     destspace=None):
    """find merge destination based on branch heads"""
    node = None

    if sourceset is None:
        sourceset = [repo[repo.dirstate.p1()].rev()]
        branch = repo.dirstate.branch()
    elif not sourceset:
        msg, hint = msgdestmerge['emptysourceset'][action]
        raise error.NoMergeDestAbort(msg, hint=hint)
    else:
        branch = None
        for ctx in repo.set('roots(%ld::%ld)', sourceset, sourceset):
            if branch is not None and ctx.branch() != branch:
                msg, hint = msgdestmerge['multiplebranchessourceset'][action]
                raise error.ManyMergeDestAbort(msg, hint=hint)
            branch = ctx.branch()

    bheads = repo.branchheads(branch)
    onhead = repo.revs('%ld and %ln', sourceset, bheads)
    if onheadcheck and not onhead:
        # Case A: working copy if not on a head. (merge only)
        #
        # This is probably a user mistake We bailout pointing at 'hg update'
        if len(repo.heads()) <= 1:
            msg, hint = msgdestmerge['nootherheadsbehind'][action]
        else:
            msg, hint = msgdestmerge['notatheads'][action]
        raise error.Abort(msg, hint=hint)
    # remove heads descendants of source from the set
    bheads = list(repo.revs('%ln - (%ld::)', bheads, sourceset))
    # filters out bookmarked heads
    nbhs = list(repo.revs('%ld - bookmark()', bheads))

    if destspace is not None:
        # restrict search space
        # used in the 'hg pull --rebase' case, see issue 5214.
        nbhs = list(repo.revs('%ld and %ld', destspace, nbhs))

    if len(nbhs) > 1:
        # Case B: There is more than 1 other anonymous heads
        #
        # This means that there will be more than 1 candidate. This is
        # ambiguous. We abort asking the user to pick as explicit destination
        # instead.
        msg, hint = msgdestmerge['toomanyheads'][action]
        msg %= (branch, len(bheads) + 1)
        raise error.ManyMergeDestAbort(msg, hint=hint)
    elif not nbhs:
        # Case B: There is no other anonymous heads
        #
        # This means that there is no natural candidate to merge with.
        # We abort, with various messages for various cases.
        if bheads:
            msg, hint = msgdestmerge['bookmarkedheads'][action]
        elif len(repo.heads()) > 1:
            msg, hint = msgdestmerge['nootherbranchheads'][action]
            msg %= branch
        elif not onhead:
            # if 'onheadcheck == False' (rebase case),
            # this was not caught in Case A.
            msg, hint = msgdestmerge['nootherheadsbehind'][action]
        else:
            msg, hint = msgdestmerge['nootherheads'][action]
        raise error.NoMergeDestAbort(msg, hint=hint)
    else:
        node = nbhs[0]
    assert node is not None
    return node

def destmerge(repo, action='merge', sourceset=None, onheadcheck=True,
              destspace=None):
    """return the default destination for a merge

    (or raise exception about why it can't pick one)

    :action: the action being performed, controls emitted error message
    """
    # destspace is here to work around issues with `hg pull --rebase` see
    # issue5214 for details
    if repo._activebookmark:
        node = _destmergebook(repo, action=action, sourceset=sourceset,
                              destspace=destspace)
    else:
        node = _destmergebranch(repo, action=action, sourceset=sourceset,
                                onheadcheck=onheadcheck, destspace=destspace)
    return repo[node].rev()

histeditdefaultrevset = 'reverse(only(.) and not public() and not ::merge())'

def desthistedit(ui, repo):
    """Default base revision to edit for `hg histedit`."""
    default = ui.config('histedit', 'defaultrev', histeditdefaultrevset)
    if default:
        revs = scmutil.revrange(repo, [default])
        if revs:
            # The revset supplied by the user may not be in ascending order nor
            # take the first revision. So do this manually.
            revs.sort()
            return revs.first()

    return None

def _statusotherbook(ui, repo):
    bmheads = repo.bookmarkheads(repo._activebookmark)
    curhead = repo[repo._activebookmark].node()
    if repo.revs('%n and parents()', curhead):
        # we are on the active bookmark
        bmheads = [b for b in bmheads if curhead != b]
        if bmheads:
            msg = _('%i other divergent bookmarks for "%s"\n')
            ui.status(msg % (len(bmheads), repo._activebookmark))

def _statusotherbranchheads(ui, repo):
    currentbranch = repo.dirstate.branch()
    allheads = repo.branchheads(currentbranch, closed=True)
    heads = repo.branchheads(currentbranch)
    if repo.revs('%ln and parents()', allheads):
        # we are on a head, even though it might be closed
        #
        #  on closed otherheads
        #  ========= ==========
        #      o        0       all heads for current branch are closed
        #               N       only descendant branch heads are closed
        #      x        0       there is only one non-closed branch head
        #               N       there are some non-closed branch heads
        #  ========= ==========
        otherheads = repo.revs('%ln - parents()', heads)
        if repo['.'].closesbranch():
            ui.warn(_('no open descendant heads on branch "%s", '
                        'updating to a closed head\n') %
                      (currentbranch))
            if otherheads:
                ui.warn(_("(committing will reopen the head, "
                            "use 'hg heads .' to see %i other heads)\n") %
                          (len(otherheads)))
            else:
                ui.warn(_('(committing will reopen branch "%s")\n') %
                          (currentbranch))
        elif otherheads:
            ui.status(_('%i other heads for branch "%s"\n') %
                      (len(otherheads), currentbranch))

def statusotherdests(ui, repo):
    """Print message about other head"""
    # XXX we should probably include a hint:
    # - about what to do
    # - how to see such heads
    if repo._activebookmark:
        _statusotherbook(ui, repo)
    else:
        _statusotherbranchheads(ui, repo)