# parser.py - simple top-down operator precedence parser for mercurial
#
# Copyright 2010 Matt Mackall <mpm@selenic.com>
#
# 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,
util,
)
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 splitargspec(spec):
"""Parse spec of function arguments into (poskeys, varkey, keys)
>>> splitargspec('')
([], None, [])
>>> splitargspec('foo bar')
([], None, ['foo', 'bar'])
>>> splitargspec('foo *bar baz')
(['foo'], 'bar', ['baz'])
>>> splitargspec('*foo')
([], 'foo', [])
"""
pre, sep, post = spec.partition('*')
pres = pre.split()
posts = post.split()
if sep:
if not posts:
raise error.ProgrammingError('no *varkey name provided')
return pres, posts[0], posts[1:]
return [], None, pres
def buildargsdict(trees, funcname, argspec, keyvaluenode, keynode):
"""Build dict from list containing positional and keyword arguments
Arguments are specified by a tuple of ``(poskeys, varkey, keys)`` where
- ``poskeys``: list of names of positional arguments
- ``varkey``: optional argument name that takes up remainder
- ``keys``: list of names that can be either positional or keyword arguments
If ``varkey`` specified, all ``keys`` must be given as keyword arguments.
Invalid keywords, too few positional arguments, or too many positional
arguments are rejected, but missing keyword arguments are just omitted.
"""
poskeys, varkey, keys = argspec
kwstart = next((i for i, x in enumerate(trees) if x[0] == keyvaluenode),
len(trees))
if kwstart < len(poskeys):
raise error.ParseError(_("%(func)s takes at least %(nargs)d positional "
"arguments")
% {'func': funcname, 'nargs': len(poskeys)})
if not varkey and len(trees) > len(poskeys) + len(keys):
raise error.ParseError(_("%(func)s takes at most %(nargs)d arguments")
% {'func': funcname,
'nargs': len(poskeys) + len(keys)})
args = {}
# consume positional arguments
for k, x in zip(poskeys, trees[:kwstart]):
args[k] = x
if varkey:
args[varkey] = trees[len(args):kwstart]
else:
for k, x in zip(keys, trees[len(args):kwstart]):
args[k] = x
# remainder should be keyword arguments
for x in trees[kwstart:]:
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 util.unescapestr(s)
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 %d: %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, [], {})