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author | Matt Harbison <matt_harbison@yahoo.com> |
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date | Sat, 01 Apr 2017 15:23:26 -0400 |
parents | afb335353d28 |
children | a98540ea1e42 |
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# 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, [], {})