annotate mercurial/utils/stringutil.py @ 43297:8a2925265402

sidedatacopies: fast path data fetching if revision has no sidedata

When using the side data mode, we know their won't be any copy information
sidedata. Skipping revision restoration give an important speed boost.

In the future, there will be other user of sidedata, reducing the efficiency of
this. We should consider adding a dedicated flag in revlog V2 to preserve this
optimisation. The current situation is good enough for now.

revision: large amount; added files: large amount; rename small amount; c3b14617fbd7 9ba6ab77fd29
before:  ! wall 2.401569 comb 2.400000 user 2.390000 sys 0.010000 (median of 10)
after:   ! wall 1.429294 comb 1.430000 user 1.410000 sys 0.020000 (median of 10)
revision: large amount; added files: small amount; rename small amount; c3b14617fbd7 f650a9b140d2
before:  ! wall 3.519140 comb 3.520000 user 3.470000 sys 0.050000 (median of 10)
after:   ! wall 1.963332 comb 1.960000 user 1.960000 sys 0.000000 (median of 10)
revision: large amount; added files: large amount; rename large amount; 08ea3258278e d9fa043f30c0
before:  ! wall 0.593880 comb 0.600000 user 0.590000 sys 0.010000 (median of 15)
after:   ! wall 0.251679 comb 0.250000 user 0.250000 sys 0.000000 (median of 38)
revision: small amount; added files: large amount; rename large amount; df6f7a526b60 a83dc6a2d56f
before:  ! wall 0.013414 comb 0.020000 user 0.020000 sys 0.000000 (median of 220)
after:   ! wall 0.013222 comb 0.020000 user 0.020000 sys 0.000000 (median of 223)
revision: small amount; added files: large amount; rename small amount; 4aa4e1f8e19a 169138063d63
before:  ! wall 0.002711 comb 0.000000 user 0.000000 sys 0.000000 (median of 1000)
after:   ! wall 0.001631 comb 0.000000 user 0.000000 sys 0.000000 (median of 1000)
revision: small amount; added files: small amount; rename small amount; 4bc173b045a6 964879152e2e
before:  ! wall 0.000077 comb 0.000000 user 0.000000 sys 0.000000 (median of 12208)
after:   ! wall 0.000078 comb 0.000000 user 0.000000 sys 0.000000 (median of 12012)
revision: medium amount; added files: large amount; rename medium amount; c95f1ced15f2 2c68e87c3efe
before:  ! wall 0.410067 comb 0.410000 user 0.410000 sys 0.000000 (median of 23)
after:   ! wall 0.207786 comb 0.200000 user 0.200000 sys 0.000000 (median of 46)
revision: medium amount; added files: medium amount; rename small amount; d343da0c55a8 d7746d32bf9d
before:  ! wall 0.097004 comb 0.090000 user 0.090000 sys 0.000000 (median of 100)
after:   ! wall 0.038495 comb 0.030000 user 0.030000 sys 0.000000 (median of 100)

Differential Revision: https://phab.mercurial-scm.org/D7074

# stringutil.py - utility for generic string formatting, parsing, etc.
#
#  Copyright 2005 K. Thananchayan <[e-mail]>
#  Copyright 2005-2007 Matt Mackall <[e-mail]>
#  Copyright 2006 Vadim Gelfer <[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 ast
import codecs
import re as remod
import textwrap
import types

from ..i18n import _
from ..thirdparty import attr

from .. import (
    encoding,
    error,
    pycompat,
)

# regex special chars pulled from https://bugs.python.org/issue29995
# which was part of Python 3.7.
_respecial = pycompat.bytestr(b'()[]{}?*+-|^$\\.&~# \t\n\r\v\f')
_regexescapemap = {ord(i): (b'\\' + i).decode('latin1') for i in _respecial}
regexbytesescapemap = {i: (b'\\' + i) for i in _respecial}


def reescape(pat):
    """Drop-in replacement for re.escape."""
    # NOTE: it is intentional that this works on unicodes and not
    # bytes, as it's only possible to do the escaping with
    # unicode.translate, not bytes.translate. Sigh.
    wantuni = True
    if isinstance(pat, bytes):
        wantuni = False
        pat = pat.decode('latin1')
    pat = pat.translate(_regexescapemap)
    if wantuni:
        return pat
    return pat.encode('latin1')


def pprint(o, bprefix=False, indent=0, level=0):
    """Pretty print an object."""
    return b''.join(pprintgen(o, bprefix=bprefix, indent=indent, level=level))


def pprintgen(o, bprefix=False, indent=0, level=0):
    """Pretty print an object to a generator of atoms.

    ``bprefix`` is a flag influencing whether bytestrings are preferred with
    a ``b''`` prefix.

    ``indent`` controls whether collections and nested data structures
    span multiple lines via the indentation amount in spaces. By default,
    no newlines are emitted.

    ``level`` specifies the initial indent level. Used if ``indent > 0``.
    """

    if isinstance(o, bytes):
        if bprefix:
            yield b"b'%s'" % escapestr(o)
        else:
            yield b"'%s'" % escapestr(o)
    elif isinstance(o, bytearray):
        # codecs.escape_encode() can't handle bytearray, so escapestr fails
        # without coercion.
        yield b"bytearray['%s']" % escapestr(bytes(o))
    elif isinstance(o, list):
        if not o:
            yield b'[]'
            return

        yield b'['

        if indent:
            level += 1
            yield b'\n'
            yield b' ' * (level * indent)

        for i, a in enumerate(o):
            for chunk in pprintgen(
                a, bprefix=bprefix, indent=indent, level=level
            ):
                yield chunk

            if i + 1 < len(o):
                if indent:
                    yield b',\n'
                    yield b' ' * (level * indent)
                else:
                    yield b', '

        if indent:
            level -= 1
            yield b'\n'
            yield b' ' * (level * indent)

        yield b']'
    elif isinstance(o, dict):
        if not o:
            yield b'{}'
            return

        yield b'{'

        if indent:
            level += 1
            yield b'\n'
            yield b' ' * (level * indent)

        for i, (k, v) in enumerate(sorted(o.items())):
            for chunk in pprintgen(
                k, bprefix=bprefix, indent=indent, level=level
            ):
                yield chunk

            yield b': '

            for chunk in pprintgen(
                v, bprefix=bprefix, indent=indent, level=level
            ):
                yield chunk

            if i + 1 < len(o):
                if indent:
                    yield b',\n'
                    yield b' ' * (level * indent)
                else:
                    yield b', '

        if indent:
            level -= 1
            yield b'\n'
            yield b' ' * (level * indent)

        yield b'}'
    elif isinstance(o, set):
        if not o:
            yield b'set([])'
            return

        yield b'set(['

        if indent:
            level += 1
            yield b'\n'
            yield b' ' * (level * indent)

        for i, k in enumerate(sorted(o)):
            for chunk in pprintgen(
                k, bprefix=bprefix, indent=indent, level=level
            ):
                yield chunk

            if i + 1 < len(o):
                if indent:
                    yield b',\n'
                    yield b' ' * (level * indent)
                else:
                    yield b', '

        if indent:
            level -= 1
            yield b'\n'
            yield b' ' * (level * indent)

        yield b'])'
    elif isinstance(o, tuple):
        if not o:
            yield b'()'
            return

        yield b'('

        if indent:
            level += 1
            yield b'\n'
            yield b' ' * (level * indent)

        for i, a in enumerate(o):
            for chunk in pprintgen(
                a, bprefix=bprefix, indent=indent, level=level
            ):
                yield chunk

            if i + 1 < len(o):
                if indent:
                    yield b',\n'
                    yield b' ' * (level * indent)
                else:
                    yield b', '

        if indent:
            level -= 1
            yield b'\n'
            yield b' ' * (level * indent)

        yield b')'
    elif isinstance(o, types.GeneratorType):
        # Special case of empty generator.
        try:
            nextitem = next(o)
        except StopIteration:
            yield b'gen[]'
            return

        yield b'gen['

        if indent:
            level += 1
            yield b'\n'
            yield b' ' * (level * indent)

        last = False

        while not last:
            current = nextitem

            try:
                nextitem = next(o)
            except StopIteration:
                last = True

            for chunk in pprintgen(
                current, bprefix=bprefix, indent=indent, level=level
            ):
                yield chunk

            if not last:
                if indent:
                    yield b',\n'
                    yield b' ' * (level * indent)
                else:
                    yield b', '

        if indent:
            level -= 1
            yield b'\n'
            yield b' ' * (level * indent)

        yield b']'
    else:
        yield pycompat.byterepr(o)


def prettyrepr(o):
    """Pretty print a representation of a possibly-nested object"""
    lines = []
    rs = pycompat.byterepr(o)
    p0 = p1 = 0
    while p0 < len(rs):
        # '... field=<type ... field=<type ...'
        #      ~~~~~~~~~~~~~~~~
        #      p0    p1        q0    q1
        q0 = -1
        q1 = rs.find(b'<', p1 + 1)
        if q1 < 0:
            q1 = len(rs)
        elif q1 > p1 + 1 and rs.startswith(b'=', q1 - 1):
            # backtrack for ' field=<'
            q0 = rs.rfind(b' ', p1 + 1, q1 - 1)
        if q0 < 0:
            q0 = q1
        else:
            q0 += 1  # skip ' '
        l = rs.count(b'<', 0, p0) - rs.count(b'>', 0, p0)
        assert l >= 0
        lines.append((l, rs[p0:q0].rstrip()))
        p0, p1 = q0, q1
    return b'\n'.join(b'  ' * l + s for l, s in lines)


def buildrepr(r):
    """Format an optional printable representation from unexpanded bits

    ========  =================================
    type(r)   example
    ========  =================================
    tuple     ('<not %r>', other)
    bytes     '<branch closed>'
    callable  lambda: '<branch %r>' % sorted(b)
    object    other
    ========  =================================
    """
    if r is None:
        return b''
    elif isinstance(r, tuple):
        return r[0] % pycompat.rapply(pycompat.maybebytestr, r[1:])
    elif isinstance(r, bytes):
        return r
    elif callable(r):
        return r()
    else:
        return pprint(r)


def binary(s):
    """return true if a string is binary data"""
    return bool(s and b'\0' in s)


def stringmatcher(pattern, casesensitive=True):
    """
    accepts a string, possibly starting with 're:' or 'literal:' prefix.
    returns the matcher name, pattern, and matcher function.
    missing or unknown prefixes are treated as literal matches.

    helper for tests:
    >>> def test(pattern, *tests):
    ...     kind, pattern, matcher = stringmatcher(pattern)
    ...     return (kind, pattern, [bool(matcher(t)) for t in tests])
    >>> def itest(pattern, *tests):
    ...     kind, pattern, matcher = stringmatcher(pattern, casesensitive=False)
    ...     return (kind, pattern, [bool(matcher(t)) for t in tests])

    exact matching (no prefix):
    >>> test(b'abcdefg', b'abc', b'def', b'abcdefg')
    ('literal', 'abcdefg', [False, False, True])

    regex matching ('re:' prefix)
    >>> test(b're:a.+b', b'nomatch', b'fooadef', b'fooadefbar')
    ('re', 'a.+b', [False, False, True])

    force exact matches ('literal:' prefix)
    >>> test(b'literal:re:foobar', b'foobar', b're:foobar')
    ('literal', 're:foobar', [False, True])

    unknown prefixes are ignored and treated as literals
    >>> test(b'foo:bar', b'foo', b'bar', b'foo:bar')
    ('literal', 'foo:bar', [False, False, True])

    case insensitive regex matches
    >>> itest(b're:A.+b', b'nomatch', b'fooadef', b'fooadefBar')
    ('re', 'A.+b', [False, False, True])

    case insensitive literal matches
    >>> itest(b'ABCDEFG', b'abc', b'def', b'abcdefg')
    ('literal', 'ABCDEFG', [False, False, True])
    """
    if pattern.startswith(b're:'):
        pattern = pattern[3:]
        try:
            flags = 0
            if not casesensitive:
                flags = remod.I
            regex = remod.compile(pattern, flags)
        except remod.error as e:
            raise error.ParseError(_(b'invalid regular expression: %s') % e)
        return b're', pattern, regex.search
    elif pattern.startswith(b'literal:'):
        pattern = pattern[8:]

    match = pattern.__eq__

    if not casesensitive:
        ipat = encoding.lower(pattern)
        match = lambda s: ipat == encoding.lower(s)
    return b'literal', pattern, match


def shortuser(user):
    """Return a short representation of a user name or email address."""
    f = user.find(b'@')
    if f >= 0:
        user = user[:f]
    f = user.find(b'<')
    if f >= 0:
        user = user[f + 1 :]
    f = user.find(b' ')
    if f >= 0:
        user = user[:f]
    f = user.find(b'.')
    if f >= 0:
        user = user[:f]
    return user


def emailuser(user):
    """Return the user portion of an email address."""
    f = user.find(b'@')
    if f >= 0:
        user = user[:f]
    f = user.find(b'<')
    if f >= 0:
        user = user[f + 1 :]
    return user


def email(author):
    '''get email of author.'''
    r = author.find(b'>')
    if r == -1:
        r = None
    return author[author.find(b'<') + 1 : r]


def person(author):
    """Returns the name before an email address,
    interpreting it as per RFC 5322

    >>> person(b'foo@bar')
    'foo'
    >>> person(b'Foo Bar <foo@bar>')
    'Foo Bar'
    >>> person(b'"Foo Bar" <foo@bar>')
    'Foo Bar'
    >>> person(b'"Foo \"buz\" Bar" <foo@bar>')
    'Foo "buz" Bar'
    >>> # The following are invalid, but do exist in real-life
    ...
    >>> person(b'Foo "buz" Bar <foo@bar>')
    'Foo "buz" Bar'
    >>> person(b'"Foo Bar <foo@bar>')
    'Foo Bar'
    """
    if b'@' not in author:
        return author
    f = author.find(b'<')
    if f != -1:
        return author[:f].strip(b' "').replace(b'\\"', b'"')
    f = author.find(b'@')
    return author[:f].replace(b'.', b' ')


@attr.s(hash=True)
class mailmapping(object):
    '''Represents a username/email key or value in
    a mailmap file'''

    email = attr.ib()
    name = attr.ib(default=None)


def _ismailmaplineinvalid(names, emails):
    '''Returns True if the parsed names and emails
    in a mailmap entry are invalid.

    >>> # No names or emails fails
    >>> names, emails = [], []
    >>> _ismailmaplineinvalid(names, emails)
    True
    >>> # Only one email fails
    >>> emails = [b'[e-mail]']
    >>> _ismailmaplineinvalid(names, emails)
    True
    >>> # One email and one name passes
    >>> names = [b'Test Name']
    >>> _ismailmaplineinvalid(names, emails)
    False
    >>> # No names but two emails passes
    >>> names = []
    >>> emails = [b'[e-mail]', b'[e-mail]']
    >>> _ismailmaplineinvalid(names, emails)
    False
    '''
    return not emails or not names and len(emails) < 2


def parsemailmap(mailmapcontent):
    """Parses data in the .mailmap format

    >>> mmdata = b"\\n".join([
    ... b'# Comment',
    ... b'Name <[e-mail]>',
    ... b'<[e-mail]> <[e-mail]>',
    ... b'Name <[e-mail]> <[e-mail]>',
    ... b'Name <[e-mail]> Commit <[e-mail]>',
    ... ])
    >>> mm = parsemailmap(mmdata)
    >>> for key in sorted(mm.keys()):
    ...     print(key)
    mailmapping(email='[e-mail]', name=None)
    mailmapping(email='[e-mail]', name=None)
    mailmapping(email='[e-mail]', name=None)
    mailmapping(email='[e-mail]', name='Commit')
    >>> for val in sorted(mm.values()):
    ...     print(val)
    mailmapping(email='[e-mail]', name='Name')
    mailmapping(email='[e-mail]', name=None)
    mailmapping(email='[e-mail]', name='Name')
    mailmapping(email='[e-mail]', name='Name')
    """
    mailmap = {}

    if mailmapcontent is None:
        return mailmap

    for line in mailmapcontent.splitlines():

        # Don't bother checking the line if it is a comment or
        # is an improperly formed author field
        if line.lstrip().startswith(b'#'):
            continue

        # names, emails hold the parsed emails and names for each line
        # name_builder holds the words in a persons name
        names, emails = [], []
        namebuilder = []

        for element in line.split():
            if element.startswith(b'#'):
                # If we reach a comment in the mailmap file, move on
                break

            elif element.startswith(b'<') and element.endswith(b'>'):
                # We have found an email.
                # Parse it, and finalize any names from earlier
                emails.append(element[1:-1])  # Slice off the "<>"

                if namebuilder:
                    names.append(b' '.join(namebuilder))
                    namebuilder = []

                # Break if we have found a second email, any other
                # data does not fit the spec for .mailmap
                if len(emails) > 1:
                    break

            else:
                # We have found another word in the committers name
                namebuilder.append(element)

        # Check to see if we have parsed the line into a valid form
        # We require at least one email, and either at least one
        # name or a second email
        if _ismailmaplineinvalid(names, emails):
            continue

        mailmapkey = mailmapping(
            email=emails[-1], name=names[-1] if len(names) == 2 else None,
        )

        mailmap[mailmapkey] = mailmapping(
            email=emails[0], name=names[0] if names else None,
        )

    return mailmap


def mapname(mailmap, author):
    """Returns the author field according to the mailmap cache, or
    the original author field.

    >>> mmdata = b"\\n".join([
    ...     b'# Comment',
    ...     b'Name <[e-mail]>',
    ...     b'<[e-mail]> <[e-mail]>',
    ...     b'Name <[e-mail]> <[e-mail]>',
    ...     b'Name <[e-mail]> Commit <[e-mail]>',
    ... ])
    >>> m = parsemailmap(mmdata)
    >>> mapname(m, b'Commit <[e-mail]>')
    'Name <[e-mail]>'
    >>> mapname(m, b'Name <[e-mail]>')
    'Name <[e-mail]>'
    >>> mapname(m, b'Commit <[e-mail]>')
    'Name <[e-mail]>'
    >>> mapname(m, b'Commit <[e-mail]>')
    'Name <[e-mail]>'
    >>> mapname(m, b'Unknown Name <[e-mail]>')
    'Unknown Name <[e-mail]>'
    """
    # If the author field coming in isn't in the correct format,
    # or the mailmap is empty just return the original author field
    if not isauthorwellformed(author) or not mailmap:
        return author

    # Turn the user name into a mailmapping
    commit = mailmapping(name=person(author), email=email(author))

    try:
        # Try and use both the commit email and name as the key
        proper = mailmap[commit]

    except KeyError:
        # If the lookup fails, use just the email as the key instead
        # We call this commit2 as not to erase original commit fields
        commit2 = mailmapping(email=commit.email)
        proper = mailmap.get(commit2, mailmapping(None, None))

    # Return the author field with proper values filled in
    return b'%s <%s>' % (
        proper.name if proper.name else commit.name,
        proper.email if proper.email else commit.email,
    )


_correctauthorformat = remod.compile(br'^[^<]+\s\<[^<>]+@[^<>]+\>$')


def isauthorwellformed(author):
    '''Return True if the author field is well formed
    (ie "Contributor Name <[e-mail]>")

    >>> isauthorwellformed(b'Good Author <[e-mail]>')
    True
    >>> isauthorwellformed(b'Author <[e-mail]>')
    True
    >>> isauthorwellformed(b'Bad Author')
    False
    >>> isauthorwellformed(b'Bad Author <[e-mail]')
    False
    >>> isauthorwellformed(b'Bad Author [e-mail]')
    False
    >>> isauthorwellformed(b'<[e-mail]>')
    False
    >>> isauthorwellformed(b'Bad Author <author>')
    False
    '''
    return _correctauthorformat.match(author) is not None


def ellipsis(text, maxlength=400):
    """Trim string to at most maxlength (default: 400) columns in display."""
    return encoding.trim(text, maxlength, ellipsis=b'...')


def escapestr(s):
    if isinstance(s, memoryview):
        s = bytes(s)
    # call underlying function of s.encode('string_escape') directly for
    # Python 3 compatibility
    return codecs.escape_encode(s)[0]


def unescapestr(s):
    return codecs.escape_decode(s)[0]


def forcebytestr(obj):
    """Portably format an arbitrary object (e.g. exception) into a byte
    string."""
    try:
        return pycompat.bytestr(obj)
    except UnicodeEncodeError:
        # non-ascii string, may be lossy
        return pycompat.bytestr(encoding.strtolocal(str(obj)))


def uirepr(s):
    # Avoid double backslash in Windows path repr()
    return pycompat.byterepr(pycompat.bytestr(s)).replace(b'\\\\', b'\\')


# delay import of textwrap
def _MBTextWrapper(**kwargs):
    class tw(textwrap.TextWrapper):
        """
        Extend TextWrapper for width-awareness.

        Neither number of 'bytes' in any encoding nor 'characters' is
        appropriate to calculate terminal columns for specified string.

        Original TextWrapper implementation uses built-in 'len()' directly,
        so overriding is needed to use width information of each characters.

        In addition, characters classified into 'ambiguous' width are
        treated as wide in East Asian area, but as narrow in other.

        This requires use decision to determine width of such characters.
        """

        def _cutdown(self, ucstr, space_left):
            l = 0
            colwidth = encoding.ucolwidth
            for i in pycompat.xrange(len(ucstr)):
                l += colwidth(ucstr[i])
                if space_left < l:
                    return (ucstr[:i], ucstr[i:])
            return ucstr, b''

        # overriding of base class
        def _handle_long_word(self, reversed_chunks, cur_line, cur_len, width):
            space_left = max(width - cur_len, 1)

            if self.break_long_words:
                cut, res = self._cutdown(reversed_chunks[-1], space_left)
                cur_line.append(cut)
                reversed_chunks[-1] = res
            elif not cur_line:
                cur_line.append(reversed_chunks.pop())

        # this overriding code is imported from TextWrapper of Python 2.6
        # to calculate columns of string by 'encoding.ucolwidth()'
        def _wrap_chunks(self, chunks):
            colwidth = encoding.ucolwidth

            lines = []
            if self.width <= 0:
                raise ValueError(b"invalid width %r (must be > 0)" % self.width)

            # Arrange in reverse order so items can be efficiently popped
            # from a stack of chucks.
            chunks.reverse()

            while chunks:

                # Start the list of chunks that will make up the current line.
                # cur_len is just the length of all the chunks in cur_line.
                cur_line = []
                cur_len = 0

                # Figure out which static string will prefix this line.
                if lines:
                    indent = self.subsequent_indent
                else:
                    indent = self.initial_indent

                # Maximum width for this line.
                width = self.width - len(indent)

                # First chunk on line is whitespace -- drop it, unless this
                # is the very beginning of the text (i.e. no lines started yet).
                if self.drop_whitespace and chunks[-1].strip() == r'' and lines:
                    del chunks[-1]

                while chunks:
                    l = colwidth(chunks[-1])

                    # Can at least squeeze this chunk onto the current line.
                    if cur_len + l <= width:
                        cur_line.append(chunks.pop())
                        cur_len += l

                    # Nope, this line is full.
                    else:
                        break

                # The current line is full, and the next chunk is too big to
                # fit on *any* line (not just this one).
                if chunks and colwidth(chunks[-1]) > width:
                    self._handle_long_word(chunks, cur_line, cur_len, width)

                # If the last chunk on this line is all whitespace, drop it.
                if (
                    self.drop_whitespace
                    and cur_line
                    and cur_line[-1].strip() == r''
                ):
                    del cur_line[-1]

                # Convert current line back to a string and store it in list
                # of all lines (return value).
                if cur_line:
                    lines.append(indent + r''.join(cur_line))

            return lines

    global _MBTextWrapper
    _MBTextWrapper = tw
    return tw(**kwargs)


def wrap(line, width, initindent=b'', hangindent=b''):
    maxindent = max(len(hangindent), len(initindent))
    if width <= maxindent:
        # adjust for weird terminal size
        width = max(78, maxindent + 1)
    line = line.decode(
        pycompat.sysstr(encoding.encoding),
        pycompat.sysstr(encoding.encodingmode),
    )
    initindent = initindent.decode(
        pycompat.sysstr(encoding.encoding),
        pycompat.sysstr(encoding.encodingmode),
    )
    hangindent = hangindent.decode(
        pycompat.sysstr(encoding.encoding),
        pycompat.sysstr(encoding.encodingmode),
    )
    wrapper = _MBTextWrapper(
        width=width, initial_indent=initindent, subsequent_indent=hangindent
    )
    return wrapper.fill(line).encode(pycompat.sysstr(encoding.encoding))


_booleans = {
    b'1': True,
    b'yes': True,
    b'true': True,
    b'on': True,
    b'always': True,
    b'0': False,
    b'no': False,
    b'false': False,
    b'off': False,
    b'never': False,
}


def parsebool(s):
    """Parse s into a boolean.

    If s is not a valid boolean, returns None.
    """
    return _booleans.get(s.lower(), None)


def evalpythonliteral(s):
    """Evaluate a string containing a Python literal expression"""
    # We could backport our tokenizer hack to rewrite '' to u'' if we want
    if pycompat.ispy3:
        return ast.literal_eval(s.decode('latin1'))
    return ast.literal_eval(s)