mercurial/parser.py

bdiff: give slight preference to appending lines

[This change could be folded into the previous changeset to minimize the repo
churn ...]

The general preference to matches in the middle of bdiff ranges helps getting
balanced recursion and efficient computation. But, as previous changes have
shown, it might also give diffs that seems "obviously wrong".

To mitigate that: If the best match on the A side starts at the beginning of
the bdiff range, don't aim for the middle-most B side match but for the
earliest.

This will make the matches balanced (by both sides being "early") even though
the bisection will be less balanced. Still, this case only apply if the *best*
and middle-most match was fully unbalanced on the A side. Each recursion will
thus even in this worst case reduce the problem significantly and we are not
re-introducing the problem that was fixed in f1ca249696ed.

The bundle size for 4.0 (hg bundle --base null -r 4.0 x.hg) happens to go from
22806817 to 22807275 bytes - a 0.002% increase.

This make the recent test-bdiff.py changes give a more pretty output ... but
they no longer show that the recursion is around middle matches (because it in
these cases isn't).

# parser.py - simple top-down operator precedence parser for mercurial
#
# Copyright 2010 Matt Mackall <[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.

# see http://effbot.org/zone/simple-top-down-parsing.htm and
# http://eli.thegreenplace.net/2010/01/02/top-down-operator-precedence-parsing/
# for background

# takes a tokenizer and elements
# tokenizer is an iterator that returns (type, value, pos) tuples
# elements is a mapping of types to binding strength, primary, prefix, infix
# and suffix actions
# an action is a tree node name, a tree label, and an optional match
# __call__(program) parses program into a labeled tree

from __future__ import absolute_import

from .i18n import _
from . import error

class parser(object):
    def __init__(self, elements, methods=None):
        self._elements = elements
        self._methods = methods
        self.current = None
    def _advance(self):
        'advance the tokenizer'
        t = self.current
        self.current = next(self._iter, None)
        return t
    def _hasnewterm(self):
        'True if next token may start new term'
        return any(self._elements[self.current[0]][1:3])
    def _match(self, m):
        'make sure the tokenizer matches an end condition'
        if self.current[0] != m:
            raise error.ParseError(_("unexpected token: %s") % self.current[0],
                                   self.current[2])
        self._advance()
    def _parseoperand(self, bind, m=None):
        'gather right-hand-side operand until an end condition or binding met'
        if m and self.current[0] == m:
            expr = None
        else:
            expr = self._parse(bind)
        if m:
            self._match(m)
        return expr
    def _parse(self, bind=0):
        token, value, pos = self._advance()
        # handle prefix rules on current token, take as primary if unambiguous
        primary, prefix = self._elements[token][1:3]
        if primary and not (prefix and self._hasnewterm()):
            expr = (primary, value)
        elif prefix:
            expr = (prefix[0], self._parseoperand(*prefix[1:]))
        else:
            raise error.ParseError(_("not a prefix: %s") % token, pos)
        # gather tokens until we meet a lower binding strength
        while bind < self._elements[self.current[0]][0]:
            token, value, pos = self._advance()
            # handle infix rules, take as suffix if unambiguous
            infix, suffix = self._elements[token][3:]
            if suffix and not (infix and self._hasnewterm()):
                expr = (suffix, expr)
            elif infix:
                expr = (infix[0], expr, self._parseoperand(*infix[1:]))
            else:
                raise error.ParseError(_("not an infix: %s") % token, pos)
        return expr
    def parse(self, tokeniter):
        'generate a parse tree from tokens'
        self._iter = tokeniter
        self._advance()
        res = self._parse()
        token, value, pos = self.current
        return res, pos
    def eval(self, tree):
        'recursively evaluate a parse tree using node methods'
        if not isinstance(tree, tuple):
            return tree
        return self._methods[tree[0]](*[self.eval(t) for t in tree[1:]])
    def __call__(self, tokeniter):
        'parse tokens into a parse tree and evaluate if methods given'
        t = self.parse(tokeniter)
        if self._methods:
            return self.eval(t)
        return t

def buildargsdict(trees, funcname, keys, keyvaluenode, keynode):
    """Build dict from list containing positional and keyword arguments

    Invalid keywords or too many positional arguments are rejected, but
    missing arguments are just omitted.
    """
    if len(trees) > len(keys):
        raise error.ParseError(_("%(func)s takes at most %(nargs)d arguments")
                               % {'func': funcname, 'nargs': len(keys)})
    args = {}
    # consume positional arguments
    for k, x in zip(keys, trees):
        if x[0] == keyvaluenode:
            break
        args[k] = x
    # remainder should be keyword arguments
    for x in trees[len(args):]:
        if x[0] != keyvaluenode or x[1][0] != keynode:
            raise error.ParseError(_("%(func)s got an invalid argument")
                                   % {'func': funcname})
        k = x[1][1]
        if k not in keys:
            raise error.ParseError(_("%(func)s got an unexpected keyword "
                                     "argument '%(key)s'")
                                   % {'func': funcname, 'key': k})
        if k in args:
            raise error.ParseError(_("%(func)s got multiple values for keyword "
                                     "argument '%(key)s'")
                                   % {'func': funcname, 'key': k})
        args[k] = x[2]
    return args

def unescapestr(s):
    try:
        return s.decode("string_escape")
    except ValueError as e:
        # mangle Python's exception into our format
        raise error.ParseError(str(e).lower())

def _prettyformat(tree, leafnodes, level, lines):
    if not isinstance(tree, tuple) or tree[0] in leafnodes:
        lines.append((level, str(tree)))
    else:
        lines.append((level, '(%s' % tree[0]))
        for s in tree[1:]:
            _prettyformat(s, leafnodes, level + 1, lines)
        lines[-1:] = [(lines[-1][0], lines[-1][1] + ')')]

def prettyformat(tree, leafnodes):
    lines = []
    _prettyformat(tree, leafnodes, 0, lines)
    output = '\n'.join(('  ' * l + s) for l, s in lines)
    return output

def simplifyinfixops(tree, targetnodes):
    """Flatten chained infix operations to reduce usage of Python stack

    >>> def f(tree):
    ...     print prettyformat(simplifyinfixops(tree, ('or',)), ('symbol',))
    >>> f(('or',
    ...     ('or',
    ...       ('symbol', '1'),
    ...       ('symbol', '2')),
    ...     ('symbol', '3')))
    (or
      ('symbol', '1')
      ('symbol', '2')
      ('symbol', '3'))
    >>> f(('func',
    ...     ('symbol', 'p1'),
    ...     ('or',
    ...       ('or',
    ...         ('func',
    ...           ('symbol', 'sort'),
    ...           ('list',
    ...             ('or',
    ...               ('or',
    ...                 ('symbol', '1'),
    ...                 ('symbol', '2')),
    ...               ('symbol', '3')),
    ...             ('negate',
    ...               ('symbol', 'rev')))),
    ...         ('and',
    ...           ('symbol', '4'),
    ...           ('group',
    ...             ('or',
    ...               ('or',
    ...                 ('symbol', '5'),
    ...                 ('symbol', '6')),
    ...               ('symbol', '7'))))),
    ...       ('symbol', '8'))))
    (func
      ('symbol', 'p1')
      (or
        (func
          ('symbol', 'sort')
          (list
            (or
              ('symbol', '1')
              ('symbol', '2')
              ('symbol', '3'))
            (negate
              ('symbol', 'rev'))))
        (and
          ('symbol', '4')
          (group
            (or
              ('symbol', '5')
              ('symbol', '6')
              ('symbol', '7'))))
        ('symbol', '8')))
    """
    if not isinstance(tree, tuple):
        return tree
    op = tree[0]
    if op not in targetnodes:
        return (op,) + tuple(simplifyinfixops(x, targetnodes) for x in tree[1:])

    # walk down left nodes taking each right node. no recursion to left nodes
    # because infix operators are left-associative, i.e. left tree is deep.
    # e.g. '1 + 2 + 3' -> (+ (+ 1 2) 3) -> (+ 1 2 3)
    simplified = []
    x = tree
    while x[0] == op:
        l, r = x[1:]
        simplified.append(simplifyinfixops(r, targetnodes))
        x = l
    simplified.append(simplifyinfixops(x, targetnodes))
    simplified.append(op)
    return tuple(reversed(simplified))

def parseerrordetail(inst):
    """Compose error message from specified ParseError object
    """
    if len(inst.args) > 1:
        return _('at %s: %s') % (inst.args[1], inst.args[0])
    else:
        return inst.args[0]

class alias(object):
    """Parsed result of alias"""

    def __init__(self, name, args, err, replacement):
        self.name = name
        self.args = args
        self.error = err
        self.replacement = replacement
        # whether own `error` information is already shown or not.
        # this avoids showing same warning multiple times at each
        # `expandaliases`.
        self.warned = False

class basealiasrules(object):
    """Parsing and expansion rule set of aliases

    This is a helper for fileset/revset/template aliases. A concrete rule set
    should be made by sub-classing this and implementing class/static methods.

    It supports alias expansion of symbol and function-call styles::

        # decl = defn
        h = heads(default)
        b($1) = ancestors($1) - ancestors(default)
    """
    # typically a config section, which will be included in error messages
    _section = None
    # tag of symbol node
    _symbolnode = 'symbol'

    def __new__(cls):
        raise TypeError("'%s' is not instantiatable" % cls.__name__)

    @staticmethod
    def _parse(spec):
        """Parse an alias name, arguments and definition"""
        raise NotImplementedError

    @staticmethod
    def _trygetfunc(tree):
        """Return (name, args) if tree is a function; otherwise None"""
        raise NotImplementedError

    @classmethod
    def _builddecl(cls, decl):
        """Parse an alias declaration into ``(name, args, errorstr)``

        This function analyzes the parsed tree. The parsing rule is provided
        by ``_parse()``.

        - ``name``: of declared alias (may be ``decl`` itself at error)
        - ``args``: list of argument names (or None for symbol declaration)
        - ``errorstr``: detail about detected error (or None)

        >>> sym = lambda x: ('symbol', x)
        >>> symlist = lambda *xs: ('list',) + tuple(sym(x) for x in xs)
        >>> func = lambda n, a: ('func', sym(n), a)
        >>> parsemap = {
        ...     'foo': sym('foo'),
        ...     '$foo': sym('$foo'),
        ...     'foo::bar': ('dagrange', sym('foo'), sym('bar')),
        ...     'foo()': func('foo', None),
        ...     '$foo()': func('$foo', None),
        ...     'foo($1, $2)': func('foo', symlist('$1', '$2')),
        ...     'foo(bar_bar, baz.baz)':
        ...         func('foo', symlist('bar_bar', 'baz.baz')),
        ...     'foo(bar($1, $2))':
        ...         func('foo', func('bar', symlist('$1', '$2'))),
        ...     'foo($1, $2, nested($1, $2))':
        ...         func('foo', (symlist('$1', '$2') +
        ...                      (func('nested', symlist('$1', '$2')),))),
        ...     'foo("bar")': func('foo', ('string', 'bar')),
        ...     'foo($1, $2': error.ParseError('unexpected token: end', 10),
        ...     'foo("bar': error.ParseError('unterminated string', 5),
        ...     'foo($1, $2, $1)': func('foo', symlist('$1', '$2', '$1')),
        ... }
        >>> def parse(expr):
        ...     x = parsemap[expr]
        ...     if isinstance(x, Exception):
        ...         raise x
        ...     return x
        >>> def trygetfunc(tree):
        ...     if not tree or tree[0] != 'func' or tree[1][0] != 'symbol':
        ...         return None
        ...     if not tree[2]:
        ...         return tree[1][1], []
        ...     if tree[2][0] == 'list':
        ...         return tree[1][1], list(tree[2][1:])
        ...     return tree[1][1], [tree[2]]
        >>> class aliasrules(basealiasrules):
        ...     _parse = staticmethod(parse)
        ...     _trygetfunc = staticmethod(trygetfunc)
        >>> builddecl = aliasrules._builddecl
        >>> builddecl('foo')
        ('foo', None, None)
        >>> builddecl('$foo')
        ('$foo', None, "invalid symbol '$foo'")
        >>> builddecl('foo::bar')
        ('foo::bar', None, 'invalid format')
        >>> builddecl('foo()')
        ('foo', [], None)
        >>> builddecl('$foo()')
        ('$foo()', None, "invalid function '$foo'")
        >>> builddecl('foo($1, $2)')
        ('foo', ['$1', '$2'], None)
        >>> builddecl('foo(bar_bar, baz.baz)')
        ('foo', ['bar_bar', 'baz.baz'], None)
        >>> builddecl('foo($1, $2, nested($1, $2))')
        ('foo($1, $2, nested($1, $2))', None, 'invalid argument list')
        >>> builddecl('foo(bar($1, $2))')
        ('foo(bar($1, $2))', None, 'invalid argument list')
        >>> builddecl('foo("bar")')
        ('foo("bar")', None, 'invalid argument list')
        >>> builddecl('foo($1, $2')
        ('foo($1, $2', None, 'at 10: unexpected token: end')
        >>> builddecl('foo("bar')
        ('foo("bar', None, 'at 5: unterminated string')
        >>> builddecl('foo($1, $2, $1)')
        ('foo', None, 'argument names collide with each other')
        """
        try:
            tree = cls._parse(decl)
        except error.ParseError as inst:
            return (decl, None, parseerrordetail(inst))

        if tree[0] == cls._symbolnode:
            # "name = ...." style
            name = tree[1]
            if name.startswith('$'):
                return (decl, None, _("invalid symbol '%s'") % name)
            return (name, None, None)

        func = cls._trygetfunc(tree)
        if func:
            # "name(arg, ....) = ...." style
            name, args = func
            if name.startswith('$'):
                return (decl, None, _("invalid function '%s'") % name)
            if any(t[0] != cls._symbolnode for t in args):
                return (decl, None, _("invalid argument list"))
            if len(args) != len(set(args)):
                return (name, None, _("argument names collide with each other"))
            return (name, [t[1] for t in args], None)

        return (decl, None, _("invalid format"))

    @classmethod
    def _relabelargs(cls, tree, args):
        """Mark alias arguments as ``_aliasarg``"""
        if not isinstance(tree, tuple):
            return tree
        op = tree[0]
        if op != cls._symbolnode:
            return (op,) + tuple(cls._relabelargs(x, args) for x in tree[1:])

        assert len(tree) == 2
        sym = tree[1]
        if sym in args:
            op = '_aliasarg'
        elif sym.startswith('$'):
            raise error.ParseError(_("invalid symbol '%s'") % sym)
        return (op, sym)

    @classmethod
    def _builddefn(cls, defn, args):
        """Parse an alias definition into a tree and marks substitutions

        This function marks alias argument references as ``_aliasarg``. The
        parsing rule is provided by ``_parse()``.

        ``args`` is a list of alias argument names, or None if the alias
        is declared as a symbol.

        >>> parsemap = {
        ...     '$1 or foo': ('or', ('symbol', '$1'), ('symbol', 'foo')),
        ...     '$1 or $bar': ('or', ('symbol', '$1'), ('symbol', '$bar')),
        ...     '$10 or baz': ('or', ('symbol', '$10'), ('symbol', 'baz')),
        ...     '"$1" or "foo"': ('or', ('string', '$1'), ('string', 'foo')),
        ... }
        >>> class aliasrules(basealiasrules):
        ...     _parse = staticmethod(parsemap.__getitem__)
        ...     _trygetfunc = staticmethod(lambda x: None)
        >>> builddefn = aliasrules._builddefn
        >>> def pprint(tree):
        ...     print prettyformat(tree, ('_aliasarg', 'string', 'symbol'))
        >>> args = ['$1', '$2', 'foo']
        >>> pprint(builddefn('$1 or foo', args))
        (or
          ('_aliasarg', '$1')
          ('_aliasarg', 'foo'))
        >>> try:
        ...     builddefn('$1 or $bar', args)
        ... except error.ParseError as inst:
        ...     print parseerrordetail(inst)
        invalid symbol '$bar'
        >>> args = ['$1', '$10', 'foo']
        >>> pprint(builddefn('$10 or baz', args))
        (or
          ('_aliasarg', '$10')
          ('symbol', 'baz'))
        >>> pprint(builddefn('"$1" or "foo"', args))
        (or
          ('string', '$1')
          ('string', 'foo'))
        """
        tree = cls._parse(defn)
        if args:
            args = set(args)
        else:
            args = set()
        return cls._relabelargs(tree, args)

    @classmethod
    def build(cls, decl, defn):
        """Parse an alias declaration and definition into an alias object"""
        repl = efmt = None
        name, args, err = cls._builddecl(decl)
        if err:
            efmt = _('bad declaration of %(section)s "%(name)s": %(error)s')
        else:
            try:
                repl = cls._builddefn(defn, args)
            except error.ParseError as inst:
                err = parseerrordetail(inst)
                efmt = _('bad definition of %(section)s "%(name)s": %(error)s')
        if err:
            err = efmt % {'section': cls._section, 'name': name, 'error': err}
        return alias(name, args, err, repl)

    @classmethod
    def buildmap(cls, items):
        """Parse a list of alias (name, replacement) pairs into a dict of
        alias objects"""
        aliases = {}
        for decl, defn in items:
            a = cls.build(decl, defn)
            aliases[a.name] = a
        return aliases

    @classmethod
    def _getalias(cls, aliases, tree):
        """If tree looks like an unexpanded alias, return (alias, pattern-args)
        pair. Return None otherwise.
        """
        if not isinstance(tree, tuple):
            return None
        if tree[0] == cls._symbolnode:
            name = tree[1]
            a = aliases.get(name)
            if a and a.args is None:
                return a, None
        func = cls._trygetfunc(tree)
        if func:
            name, args = func
            a = aliases.get(name)
            if a and a.args is not None:
                return a, args
        return None

    @classmethod
    def _expandargs(cls, tree, args):
        """Replace _aliasarg instances with the substitution value of the
        same name in args, recursively.
        """
        if not isinstance(tree, tuple):
            return tree
        if tree[0] == '_aliasarg':
            sym = tree[1]
            return args[sym]
        return tuple(cls._expandargs(t, args) for t in tree)

    @classmethod
    def _expand(cls, aliases, tree, expanding, cache):
        if not isinstance(tree, tuple):
            return tree
        r = cls._getalias(aliases, tree)
        if r is None:
            return tuple(cls._expand(aliases, t, expanding, cache)
                         for t in tree)
        a, l = r
        if a.error:
            raise error.Abort(a.error)
        if a in expanding:
            raise error.ParseError(_('infinite expansion of %(section)s '
                                     '"%(name)s" detected')
                                   % {'section': cls._section, 'name': a.name})
        # get cacheable replacement tree by expanding aliases recursively
        expanding.append(a)
        if a.name not in cache:
            cache[a.name] = cls._expand(aliases, a.replacement, expanding,
                                        cache)
        result = cache[a.name]
        expanding.pop()
        if a.args is None:
            return result
        # substitute function arguments in replacement tree
        if len(l) != len(a.args):
            raise error.ParseError(_('invalid number of arguments: %d')
                                   % len(l))
        l = [cls._expand(aliases, t, [], cache) for t in l]
        return cls._expandargs(result, dict(zip(a.args, l)))

    @classmethod
    def expand(cls, aliases, tree):
        """Expand aliases in tree, recursively.

        'aliases' is a dictionary mapping user defined aliases to alias objects.
        """
        return cls._expand(aliases, tree, [], {})