view mercurial/dagparser.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

# dagparser.py - parser and generator for concise description of DAGs
#
# Copyright 2010 Peter Arrenbrecht <[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 re
import string

from .i18n import _
from . import (
    error,
    pycompat,
)
from .utils import stringutil


def parsedag(desc):
    '''parses a DAG from a concise textual description; generates events

    "+n" is a linear run of n nodes based on the current default parent
    "." is a single node based on the current default parent
    "$" resets the default parent to -1 (implied at the start);
        otherwise the default parent is always the last node created
    "<p" sets the default parent to the backref p
    "*p" is a fork at parent p, where p is a backref
    "*p1/p2/.../pn" is a merge of parents p1..pn, where the pi are backrefs
    "/p2/.../pn" is a merge of the preceding node and p2..pn
    ":name" defines a label for the preceding node; labels can be redefined
    "@text" emits an annotation event for text
    "!command" emits an action event for the current node
    "!!my command\n" is like "!", but to the end of the line
    "#...\n" is a comment up to the end of the line

    Whitespace between the above elements is ignored.

    A backref is either
     * a number n, which references the node curr-n, where curr is the current
       node, or
     * the name of a label you placed earlier using ":name", or
     * empty to denote the default parent.

    All string valued-elements are either strictly alphanumeric, or must
    be enclosed in double quotes ("..."), with "\" as escape character.

    Generates sequence of

      ('n', (id, [parentids])) for node creation
      ('l', (id, labelname)) for labels on nodes
      ('a', text) for annotations
      ('c', command) for actions (!)
      ('C', command) for line actions (!!)

    Examples
    --------

    Example of a complex graph (output not shown for brevity):

        >>> len(list(parsedag(b"""
        ...
        ... +3         # 3 nodes in linear run
        ... :forkhere  # a label for the last of the 3 nodes from above
        ... +5         # 5 more nodes on one branch
        ... :mergethis # label again
        ... <forkhere  # set default parent to labeled fork node
        ... +10        # 10 more nodes on a parallel branch
        ... @stable    # following nodes will be annotated as "stable"
        ... +5         # 5 nodes in stable
        ... !addfile   # custom command; could trigger new file in next node
        ... +2         # two more nodes
        ... /mergethis # merge last node with labeled node
        ... +4         # 4 more nodes descending from merge node
        ...
        ... """)))
        34

    Empty list:

        >>> list(parsedag(b""))
        []

    A simple linear run:

        >>> list(parsedag(b"+3"))
        [('n', (0, [-1])), ('n', (1, [0])), ('n', (2, [1]))]

    Some non-standard ways to define such runs:

        >>> list(parsedag(b"+1+2"))
        [('n', (0, [-1])), ('n', (1, [0])), ('n', (2, [1]))]

        >>> list(parsedag(b"+1*1*"))
        [('n', (0, [-1])), ('n', (1, [0])), ('n', (2, [1]))]

        >>> list(parsedag(b"*"))
        [('n', (0, [-1]))]

        >>> list(parsedag(b"..."))
        [('n', (0, [-1])), ('n', (1, [0])), ('n', (2, [1]))]

    A fork and a join, using numeric back references:

        >>> list(parsedag(b"+2*2*/2"))
        [('n', (0, [-1])), ('n', (1, [0])), ('n', (2, [0])), ('n', (3, [2, 1]))]

        >>> list(parsedag(b"+2<2+1/2"))
        [('n', (0, [-1])), ('n', (1, [0])), ('n', (2, [0])), ('n', (3, [2, 1]))]

    Placing a label:

        >>> list(parsedag(b"+1 :mylabel +1"))
        [('n', (0, [-1])), ('l', (0, 'mylabel')), ('n', (1, [0]))]

    An empty label (silly, really):

        >>> list(parsedag(b"+1:+1"))
        [('n', (0, [-1])), ('l', (0, '')), ('n', (1, [0]))]

    Fork and join, but with labels instead of numeric back references:

        >>> list(parsedag(b"+1:f +1:p2 *f */p2"))
        [('n', (0, [-1])), ('l', (0, 'f')), ('n', (1, [0])), ('l', (1, 'p2')),
         ('n', (2, [0])), ('n', (3, [2, 1]))]

        >>> list(parsedag(b"+1:f +1:p2 <f +1 /p2"))
        [('n', (0, [-1])), ('l', (0, 'f')), ('n', (1, [0])), ('l', (1, 'p2')),
         ('n', (2, [0])), ('n', (3, [2, 1]))]

    Restarting from the root:

        >>> list(parsedag(b"+1 $ +1"))
        [('n', (0, [-1])), ('n', (1, [-1]))]

    Annotations, which are meant to introduce sticky state for subsequent nodes:

        >>> list(parsedag(b"+1 @ann +1"))
        [('n', (0, [-1])), ('a', 'ann'), ('n', (1, [0]))]

        >>> list(parsedag(b'+1 @"my annotation" +1'))
        [('n', (0, [-1])), ('a', 'my annotation'), ('n', (1, [0]))]

    Commands, which are meant to operate on the most recently created node:

        >>> list(parsedag(b"+1 !cmd +1"))
        [('n', (0, [-1])), ('c', 'cmd'), ('n', (1, [0]))]

        >>> list(parsedag(b'+1 !"my command" +1'))
        [('n', (0, [-1])), ('c', 'my command'), ('n', (1, [0]))]

        >>> list(parsedag(b'+1 !!my command line\\n +1'))
        [('n', (0, [-1])), ('C', 'my command line'), ('n', (1, [0]))]

    Comments, which extend to the end of the line:

        >>> list(parsedag(b'+1 # comment\\n+1'))
        [('n', (0, [-1])), ('n', (1, [0]))]

    Error:

        >>> try: list(parsedag(b'+1 bad'))
        ... except Exception as e: print(pycompat.sysstr(bytes(e)))
        invalid character in dag description: bad...

    '''
    if not desc:
        return

    # pytype: disable=wrong-arg-types
    wordchars = pycompat.bytestr(string.ascii_letters + string.digits)
    # pytype: enable=wrong-arg-types

    labels = {}
    p1 = -1
    r = 0

    def resolve(ref):
        if not ref:
            return p1
        # pytype: disable=wrong-arg-types
        elif ref[0] in pycompat.bytestr(string.digits):
            # pytype: enable=wrong-arg-types
            return r - int(ref)
        else:
            return labels[ref]

    chiter = pycompat.iterbytestr(desc)

    def nextch():
        return next(chiter, b'\0')

    def nextrun(c, allow):
        s = b''
        while c in allow:
            s += c
            c = nextch()
        return c, s

    def nextdelimited(c, limit, escape):
        s = b''
        while c != limit:
            if c == escape:
                c = nextch()
            s += c
            c = nextch()
        return nextch(), s

    def nextstring(c):
        if c == b'"':
            return nextdelimited(nextch(), b'"', b'\\')
        else:
            return nextrun(c, wordchars)

    c = nextch()
    while c != b'\0':
        # pytype: disable=wrong-arg-types
        while c in pycompat.bytestr(string.whitespace):
            # pytype: enable=wrong-arg-types
            c = nextch()
        if c == b'.':
            yield b'n', (r, [p1])
            p1 = r
            r += 1
            c = nextch()
        elif c == b'+':
            # pytype: disable=wrong-arg-types
            c, digs = nextrun(nextch(), pycompat.bytestr(string.digits))
            # pytype: enable=wrong-arg-types
            n = int(digs)
            for i in pycompat.xrange(0, n):
                yield b'n', (r, [p1])
                p1 = r
                r += 1
        elif c in b'*/':
            if c == b'*':
                c = nextch()
            c, pref = nextstring(c)
            prefs = [pref]
            while c == b'/':
                c, pref = nextstring(nextch())
                prefs.append(pref)
            ps = [resolve(ref) for ref in prefs]
            yield b'n', (r, ps)
            p1 = r
            r += 1
        elif c == b'<':
            c, ref = nextstring(nextch())
            p1 = resolve(ref)
        elif c == b':':
            c, name = nextstring(nextch())
            labels[name] = p1
            yield b'l', (p1, name)
        elif c == b'@':
            c, text = nextstring(nextch())
            yield b'a', text
        elif c == b'!':
            c = nextch()
            if c == b'!':
                cmd = b''
                c = nextch()
                while c not in b'\n\r\0':
                    cmd += c
                    c = nextch()
                yield b'C', cmd
            else:
                c, cmd = nextstring(c)
                yield b'c', cmd
        elif c == b'#':
            while c not in b'\n\r\0':
                c = nextch()
        elif c == b'$':
            p1 = -1
            c = nextch()
        elif c == b'\0':
            return  # in case it was preceded by whitespace
        else:
            s = b''
            i = 0
            while c != b'\0' and i < 10:
                s += c
                i += 1
                c = nextch()
            raise error.Abort(
                _(b'invalid character in dag description: %s...') % s
            )


def dagtextlines(
    events,
    addspaces=True,
    wraplabels=False,
    wrapannotations=False,
    wrapcommands=False,
    wrapnonlinear=False,
    usedots=False,
    maxlinewidth=70,
):
    '''generates single lines for dagtext()'''

    def wrapstring(text):
        if re.match(b"^[0-9a-z]*$", text):
            return text
        return b'"' + text.replace(b'\\', b'\\\\').replace(b'"', b'\"') + b'"'

    def gen():
        labels = {}
        run = 0
        wantr = 0
        needroot = False
        for kind, data in events:
            if kind == b'n':
                r, ps = data

                # sanity check
                if r != wantr:
                    raise error.Abort(_(b"expected id %i, got %i") % (wantr, r))
                if not ps:
                    ps = [-1]
                else:
                    for p in ps:
                        if p >= r:
                            raise error.Abort(
                                _(
                                    b"parent id %i is larger than "
                                    b"current id %i"
                                )
                                % (p, r)
                            )
                wantr += 1

                # new root?
                p1 = r - 1
                if len(ps) == 1 and ps[0] == -1:
                    if needroot:
                        if run:
                            yield b'+%d' % run
                            run = 0
                        if wrapnonlinear:
                            yield b'\n'
                        yield b'$'
                        p1 = -1
                    else:
                        needroot = True
                if len(ps) == 1 and ps[0] == p1:
                    if usedots:
                        yield b"."
                    else:
                        run += 1
                else:
                    if run:
                        yield b'+%d' % run
                        run = 0
                    if wrapnonlinear:
                        yield b'\n'
                    prefs = []
                    for p in ps:
                        if p == p1:
                            prefs.append(b'')
                        elif p in labels:
                            prefs.append(labels[p])
                        else:
                            prefs.append(b'%d' % (r - p))
                    yield b'*' + b'/'.join(prefs)
            else:
                if run:
                    yield b'+%d' % run
                    run = 0
                if kind == b'l':
                    rid, name = data
                    labels[rid] = name
                    yield b':' + name
                    if wraplabels:
                        yield b'\n'
                elif kind == b'c':
                    yield b'!' + wrapstring(data)
                    if wrapcommands:
                        yield b'\n'
                elif kind == b'C':
                    yield b'!!' + data
                    yield b'\n'
                elif kind == b'a':
                    if wrapannotations:
                        yield b'\n'
                    yield b'@' + wrapstring(data)
                elif kind == b'#':
                    yield b'#' + data
                    yield b'\n'
                else:
                    raise error.Abort(
                        _(b"invalid event type in dag: ('%s', '%s')")
                        % (
                            stringutil.escapestr(kind),
                            stringutil.escapestr(data),
                        )
                    )
        if run:
            yield b'+%d' % run

    line = b''
    for part in gen():
        if part == b'\n':
            if line:
                yield line
                line = b''
        else:
            if len(line) + len(part) >= maxlinewidth:
                yield line
                line = b''
            elif addspaces and line and part != b'.':
                line += b' '
            line += part
    if line:
        yield line


def dagtext(
    dag,
    addspaces=True,
    wraplabels=False,
    wrapannotations=False,
    wrapcommands=False,
    wrapnonlinear=False,
    usedots=False,
    maxlinewidth=70,
):
    """generates lines of a textual representation for a dag event stream

    events should generate what parsedag() does, so:

      ('n', (id, [parentids])) for node creation
      ('l', (id, labelname)) for labels on nodes
      ('a', text) for annotations
      ('c', text) for commands
      ('C', text) for line commands ('!!')
      ('#', text) for comment lines

    Parent nodes must come before child nodes.

    Examples
    --------

    Linear run:

        >>> dagtext([(b'n', (0, [-1])), (b'n', (1, [0]))])
        '+2'

    Two roots:

        >>> dagtext([(b'n', (0, [-1])), (b'n', (1, [-1]))])
        '+1 $ +1'

    Fork and join:

        >>> dagtext([(b'n', (0, [-1])), (b'n', (1, [0])), (b'n', (2, [0])),
        ...          (b'n', (3, [2, 1]))])
        '+2 *2 */2'

    Fork and join with labels:

        >>> dagtext([(b'n', (0, [-1])), (b'l', (0, b'f')), (b'n', (1, [0])),
        ...          (b'l', (1, b'p2')), (b'n', (2, [0])), (b'n', (3, [2, 1]))])
        '+1 :f +1 :p2 *f */p2'

    Annotations:

        >>> dagtext([(b'n', (0, [-1])), (b'a', b'ann'), (b'n', (1, [0]))])
        '+1 @ann +1'

        >>> dagtext([(b'n', (0, [-1])),
        ...          (b'a', b'my annotation'),
        ...          (b'n', (1, [0]))])
        '+1 @"my annotation" +1'

    Commands:

        >>> dagtext([(b'n', (0, [-1])), (b'c', b'cmd'), (b'n', (1, [0]))])
        '+1 !cmd +1'

        >>> dagtext([(b'n', (0, [-1])),
        ...          (b'c', b'my command'),
        ...          (b'n', (1, [0]))])
        '+1 !"my command" +1'

        >>> dagtext([(b'n', (0, [-1])),
        ...          (b'C', b'my command line'),
        ...          (b'n', (1, [0]))])
        '+1 !!my command line\\n+1'

    Comments:

        >>> dagtext([(b'n', (0, [-1])), (b'#', b' comment'), (b'n', (1, [0]))])
        '+1 # comment\\n+1'

        >>> dagtext([])
        ''

    Combining parsedag and dagtext:

        >>> dagtext(parsedag(b'+1 :f +1 :p2 *f */p2'))
        '+1 :f +1 :p2 *f */p2'

    """
    return b"\n".join(
        dagtextlines(
            dag,
            addspaces,
            wraplabels,
            wrapannotations,
            wrapcommands,
            wrapnonlinear,
            usedots,
            maxlinewidth,
        )
    )