tests/testlib/ext-sidedata.py

dirstate-tree: Add tree traversal/iteration

Like Python’s, Rust’s iterators are "external" in that they are driven
by a caller who calls a `next` method. This is as opposed to "internal"
iterators who drive themselves and call a callback for each item.

Writing an internal iterator traversing a tree is easy with recursion,
but internal iterators cannot rely on the call stack in that way,
they must save in an explicit object all state that they need to be
preserved across two `next` calls.

This algorithm uses a `Vec` as a stack that contains what would be
local variables on the call stack if we could use recursion.

Differential Revision: https://phab.mercurial-scm.org/D10370

# ext-sidedata.py - small extension to test the sidedata logic
#
# Copyright 2019 Pierre-Yves David <[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 __future__ import absolute_import

import hashlib
import struct

from mercurial.node import nullrev
from mercurial import (
    extensions,
    requirements,
    revlog,
)

from mercurial.upgrade_utils import engine as upgrade_engine

from mercurial.revlogutils import constants
from mercurial.revlogutils import sidedata


def wrapaddrevision(
    orig, self, text, transaction, link, p1, p2, *args, **kwargs
):
    if kwargs.get('sidedata') is None:
        kwargs['sidedata'] = {}
    sd = kwargs['sidedata']
    ## let's store some arbitrary data just for testing
    # text length
    sd[sidedata.SD_TEST1] = struct.pack('>I', len(text))
    # and sha2 hashes
    sha256 = hashlib.sha256(text).digest()
    sd[sidedata.SD_TEST2] = struct.pack('>32s', sha256)
    return orig(self, text, transaction, link, p1, p2, *args, **kwargs)


def wrap_revisiondata(orig, self, nodeorrev, *args, **kwargs):
    text, sd = orig(self, nodeorrev, *args, **kwargs)
    if getattr(self, 'sidedatanocheck', False):
        return text, sd
    if self.version & 0xFFFF != 2:
        return text, sd
    if nodeorrev != nullrev and nodeorrev != self.nullid:
        cat1 = sd.get(sidedata.SD_TEST1)
        if cat1 is not None and len(text) != struct.unpack('>I', cat1)[0]:
            raise RuntimeError('text size mismatch')
        expected = sd.get(sidedata.SD_TEST2)
        got = hashlib.sha256(text).digest()
        if expected is not None and got != expected:
            raise RuntimeError('sha256 mismatch')
    return text, sd


def wrapget_sidedata_helpers(orig, srcrepo, dstrepo):
    repo, computers, removers = orig(srcrepo, dstrepo)
    assert not computers and not removers  # deal with composition later
    addedreqs = dstrepo.requirements - srcrepo.requirements

    if requirements.SIDEDATA_REQUIREMENT in addedreqs:

        def computer(repo, revlog, rev, old_sidedata):
            assert not old_sidedata  # not supported yet
            update = {}
            revlog.sidedatanocheck = True
            try:
                text = revlog.revision(rev)
            finally:
                del revlog.sidedatanocheck
            ## let's store some arbitrary data just for testing
            # text length
            update[sidedata.SD_TEST1] = struct.pack('>I', len(text))
            # and sha2 hashes
            sha256 = hashlib.sha256(text).digest()
            update[sidedata.SD_TEST2] = struct.pack('>32s', sha256)
            return update, (0, 0)

        srcrepo.register_sidedata_computer(
            constants.KIND_CHANGELOG,
            b"whatever",
            (sidedata.SD_TEST1, sidedata.SD_TEST2),
            computer,
            0,
        )
        dstrepo.register_wanted_sidedata(b"whatever")

    return sidedata.get_sidedata_helpers(srcrepo, dstrepo._wanted_sidedata)


def extsetup(ui):
    extensions.wrapfunction(revlog.revlog, 'addrevision', wrapaddrevision)
    extensions.wrapfunction(revlog.revlog, '_revisiondata', wrap_revisiondata)
    extensions.wrapfunction(
        upgrade_engine, 'get_sidedata_helpers', wrapget_sidedata_helpers
    )


def reposetup(ui, repo):
    # We don't register sidedata computers because we don't care within these
    # tests
    repo.register_wanted_sidedata(sidedata.SD_TEST1)
    repo.register_wanted_sidedata(sidedata.SD_TEST2)