view hgext/convert/darcs.py @ 49000:dd6b67d5c256 stable

rust: fix unsound `OwningDirstateMap`

As per the previous patch, `OwningDirstateMap` is unsound. Self-referential
structs are difficult to implement correctly in Rust since the compiler is
free to move structs around as much as it wants to. They are also very rarely
needed in practice, so the state-of-the-art on how they should be done within
the Rust rules is still a bit new.

The crate `ouroboros` is an attempt at providing a safe way (in the Rust sense)
of declaring self-referential structs. It is getting a lot attention and was
improved very quickly when soundness issues were found in the past: rather than
relying on our own (limited) review circle, we might as well use the de-facto
common crate to fix this problem. This will give us a much better chance of
finding issues should any new ones be discovered as well as the benefit of
fewer `unsafe` APIs of our own.

I was starting to think about how I would present a safe API to the old struct
but soon realized that the callback-based approach was already done in
`ouroboros`, along with a lot more care towards refusing incorrect structs.

In short: we don't return a mutable reference to the `DirstateMap` anymore, we
expect users of its API to pass a `FnOnce` that takes the map as an argument.
This allows our `OwningDirstateMap` to control the input and output lifetimes
of the code that modifies it to prevent such issues.

Changing to `ouroboros` meant changing every API with it, but it is relatively
low churn in the end. It correctly identified the example buggy modification of
`copy_map_insert` outlined in the previous patch as violating the borrow rules.

Differential Revision: https://phab.mercurial-scm.org/D12429

# darcs.py - darcs support for the convert extension
#
#  Copyright 2007-2009 Olivia Mackall <[e-mail]> and others
#
# 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 errno
import os
import re
import shutil

from mercurial.i18n import _
from mercurial import (
    error,
    pycompat,
    util,
)
from mercurial.utils import dateutil
from . import common

NoRepo = common.NoRepo

# The naming drift of ElementTree is fun!

try:
    import xml.etree.cElementTree.ElementTree as ElementTree
    import xml.etree.cElementTree.XMLParser as XMLParser
except ImportError:
    try:
        import xml.etree.ElementTree.ElementTree as ElementTree
        import xml.etree.ElementTree.XMLParser as XMLParser
    except ImportError:
        try:
            import elementtree.cElementTree.ElementTree as ElementTree
            import elementtree.cElementTree.XMLParser as XMLParser
        except ImportError:
            try:
                import elementtree.ElementTree.ElementTree as ElementTree
                import elementtree.ElementTree.XMLParser as XMLParser
            except ImportError:
                pass


class darcs_source(common.converter_source, common.commandline):
    def __init__(self, ui, repotype, path, revs=None):
        common.converter_source.__init__(self, ui, repotype, path, revs=revs)
        common.commandline.__init__(self, ui, b'darcs')

        # check for _darcs, ElementTree so that we can easily skip
        # test-convert-darcs if ElementTree is not around
        if not os.path.exists(os.path.join(path, b'_darcs')):
            raise NoRepo(_(b"%s does not look like a darcs repository") % path)

        common.checktool(b'darcs')
        version = self.run0(b'--version').splitlines()[0].strip()
        if version < b'2.1':
            raise error.Abort(
                _(b'darcs version 2.1 or newer needed (found %r)') % version
            )

        if b"ElementTree" not in globals():
            raise error.Abort(_(b"Python ElementTree module is not available"))

        self.path = os.path.realpath(path)

        self.lastrev = None
        self.changes = {}
        self.parents = {}
        self.tags = {}

        # Check darcs repository format
        format = self.format()
        if format:
            if format in (b'darcs-1.0', b'hashed'):
                raise NoRepo(
                    _(
                        b"%s repository format is unsupported, "
                        b"please upgrade"
                    )
                    % format
                )
        else:
            self.ui.warn(_(b'failed to detect repository format!'))

    def before(self):
        self.tmppath = pycompat.mkdtemp(
            prefix=b'convert-' + os.path.basename(self.path) + b'-'
        )
        output, status = self.run(b'init', repodir=self.tmppath)
        self.checkexit(status)

        tree = self.xml(
            b'changes', xml_output=True, summary=True, repodir=self.path
        )
        tagname = None
        child = None
        for elt in tree.findall(b'patch'):
            node = elt.get(b'hash')
            name = elt.findtext(b'name', b'')
            if name.startswith(b'TAG '):
                tagname = name[4:].strip()
            elif tagname is not None:
                self.tags[tagname] = node
                tagname = None
            self.changes[node] = elt
            self.parents[child] = [node]
            child = node
        self.parents[child] = []

    def after(self):
        self.ui.debug(b'cleaning up %s\n' % self.tmppath)
        shutil.rmtree(self.tmppath, ignore_errors=True)

    def recode(self, s, encoding=None):
        if isinstance(s, pycompat.unicode):
            # XMLParser returns unicode objects for anything it can't
            # encode into ASCII. We convert them back to str to get
            # recode's normal conversion behavior.
            s = s.encode('latin-1')
        return super(darcs_source, self).recode(s, encoding)

    def xml(self, cmd, **kwargs):
        # NOTE: darcs is currently encoding agnostic and will print
        # patch metadata byte-for-byte, even in the XML changelog.
        etree = ElementTree()
        # While we are decoding the XML as latin-1 to be as liberal as
        # possible, etree will still raise an exception if any
        # non-printable characters are in the XML changelog.
        parser = XMLParser(encoding=b'latin-1')
        p = self._run(cmd, **kwargs)
        etree.parse(p.stdout, parser=parser)
        p.wait()
        self.checkexit(p.returncode)
        return etree.getroot()

    def format(self):
        output, status = self.run(b'show', b'repo', repodir=self.path)
        self.checkexit(status)
        m = re.search(r'^\s*Format:\s*(.*)$', output, re.MULTILINE)
        if not m:
            return None
        return b','.join(sorted(f.strip() for f in m.group(1).split(b',')))

    def manifest(self):
        man = []
        output, status = self.run(
            b'show', b'files', no_directories=True, repodir=self.tmppath
        )
        self.checkexit(status)
        for line in output.split(b'\n'):
            path = line[2:]
            if path:
                man.append(path)
        return man

    def getheads(self):
        return self.parents[None]

    def getcommit(self, rev):
        elt = self.changes[rev]
        dateformat = b'%a %b %d %H:%M:%S %Z %Y'
        date = dateutil.strdate(elt.get(b'local_date'), dateformat)
        desc = elt.findtext(b'name') + b'\n' + elt.findtext(b'comment', b'')
        # etree can return unicode objects for name, comment, and author,
        # so recode() is used to ensure str objects are emitted.
        newdateformat = b'%Y-%m-%d %H:%M:%S %1%2'
        return common.commit(
            author=self.recode(elt.get(b'author')),
            date=dateutil.datestr(date, newdateformat),
            desc=self.recode(desc).strip(),
            parents=self.parents[rev],
        )

    def pull(self, rev):
        output, status = self.run(
            b'pull',
            self.path,
            all=True,
            match=b'hash %s' % rev,
            no_test=True,
            no_posthook=True,
            external_merge=b'/bin/false',
            repodir=self.tmppath,
        )
        if status:
            if output.find(b'We have conflicts in') == -1:
                self.checkexit(status, output)
            output, status = self.run(b'revert', all=True, repodir=self.tmppath)
            self.checkexit(status, output)

    def getchanges(self, rev, full):
        if full:
            raise error.Abort(_(b"convert from darcs does not support --full"))
        copies = {}
        changes = []
        man = None
        for elt in self.changes[rev].find(b'summary').getchildren():
            if elt.tag in (b'add_directory', b'remove_directory'):
                continue
            if elt.tag == b'move':
                if man is None:
                    man = self.manifest()
                source, dest = elt.get(b'from'), elt.get(b'to')
                if source in man:
                    # File move
                    changes.append((source, rev))
                    changes.append((dest, rev))
                    copies[dest] = source
                else:
                    # Directory move, deduce file moves from manifest
                    source = source + b'/'
                    for f in man:
                        if not f.startswith(source):
                            continue
                        fdest = dest + b'/' + f[len(source) :]
                        changes.append((f, rev))
                        changes.append((fdest, rev))
                        copies[fdest] = f
            else:
                changes.append((elt.text.strip(), rev))
        self.pull(rev)
        self.lastrev = rev
        return sorted(changes), copies, set()

    def getfile(self, name, rev):
        if rev != self.lastrev:
            raise error.Abort(_(b'internal calling inconsistency'))
        path = os.path.join(self.tmppath, name)
        try:
            data = util.readfile(path)
            mode = os.lstat(path).st_mode
        except IOError as inst:
            if inst.errno == errno.ENOENT:
                return None, None
            raise
        mode = (mode & 0o111) and b'x' or b''
        return data, mode

    def gettags(self):
        return self.tags