X-Git-Url: https://git.madduck.net/etc/vim.git/blobdiff_plain/b3ceb293d9e69295a190fed93517cbe1b7372154..eb9d0396cd51065c975e366f06dfea60221a2d03:/src/blib2to3/pgen2/parse.py diff --git a/src/blib2to3/pgen2/parse.py b/src/blib2to3/pgen2/parse.py index 47c8f02..dc40526 100644 --- a/src/blib2to3/pgen2/parse.py +++ b/src/blib2to3/pgen2/parse.py @@ -9,22 +9,31 @@ See Parser/parser.c in the Python distribution for additional info on how this parsing engine works. """ +import copy +from contextlib import contextmanager # Local imports -from . import token +from . import grammar, token, tokenize from typing import ( + cast, + Any, Optional, Text, Union, Tuple, Dict, List, + Iterator, Callable, Set, + TYPE_CHECKING, ) from blib2to3.pgen2.grammar import Grammar from blib2to3.pytree import NL, Context, RawNode, Leaf, Node +if TYPE_CHECKING: + from blib2to3.driver import TokenProxy + Results = Dict[Text, NL] Convert = Callable[[Grammar, RawNode], Union[Node, Leaf]] @@ -37,6 +46,61 @@ def lam_sub(grammar: Grammar, node: RawNode) -> NL: return Node(type=node[0], children=node[3], context=node[2]) +class Recorder: + def __init__(self, parser: "Parser", ilabels: List[int], context: Context) -> None: + self.parser = parser + self._ilabels = ilabels + self.context = context # not really matter + + self._dead_ilabels: Set[int] = set() + self._start_point = copy.deepcopy(self.parser.stack) + self._points = {ilabel: copy.deepcopy(self._start_point) for ilabel in ilabels} + + @property + def ilabels(self) -> Set[int]: + return self._dead_ilabels.symmetric_difference(self._ilabels) + + @contextmanager + def switch_to(self, ilabel: int) -> Iterator[None]: + self.parser.stack = self._points[ilabel] + try: + yield + except ParseError: + self._dead_ilabels.add(ilabel) + finally: + self.parser.stack = self._start_point + + def add_token( + self, tok_type: int, tok_val: Optional[Text], raw: bool = False + ) -> None: + func: Callable[..., Any] + if raw: + func = self.parser._addtoken + else: + func = self.parser.addtoken + + for ilabel in self.ilabels: + with self.switch_to(ilabel): + args = [tok_type, tok_val, self.context] + if raw: + args.insert(0, ilabel) + func(*args) + + def determine_route( + self, value: Optional[Text] = None, force: bool = False + ) -> Optional[int]: + alive_ilabels = self.ilabels + if len(alive_ilabels) == 0: + *_, most_successful_ilabel = self._dead_ilabels + raise ParseError("bad input", most_successful_ilabel, value, self.context) + + ilabel, *rest = alive_ilabels + if force or not rest: + return ilabel + else: + return None + + class ParseError(Exception): """Exception to signal the parser is stuck.""" @@ -114,7 +178,7 @@ class Parser(object): self.grammar = grammar self.convert = convert or lam_sub - def setup(self, start: Optional[int] = None) -> None: + def setup(self, proxy: "TokenProxy", start: Optional[int] = None) -> None: """Prepare for parsing. This *must* be called before starting to parse. @@ -137,11 +201,55 @@ class Parser(object): self.stack: List[Tuple[DFAS, int, RawNode]] = [stackentry] self.rootnode: Optional[NL] = None self.used_names: Set[str] = set() + self.proxy = proxy def addtoken(self, type: int, value: Optional[Text], context: Context) -> bool: """Add a token; return True iff this is the end of the program.""" # Map from token to label - ilabel = self.classify(type, value, context) + ilabels = self.classify(type, value, context) + assert len(ilabels) >= 1 + + # If we have only one state to advance, we'll directly + # take it as is. + if len(ilabels) == 1: + [ilabel] = ilabels + return self._addtoken(ilabel, type, value, context) + + # If there are multiple states which we can advance (only + # happen under soft-keywords), then we will try all of them + # in parallel and as soon as one state can reach further than + # the rest, we'll choose that one. This is a pretty hacky + # and hopefully temporary algorithm. + # + # For a more detailed explanation, check out this post: + # https://tree.science/what-the-backtracking.html + + with self.proxy.release() as proxy: + counter, force = 0, False + recorder = Recorder(self, ilabels, context) + recorder.add_token(type, value, raw=True) + + next_token_value = value + while recorder.determine_route(next_token_value) is None: + if not proxy.can_advance(counter): + force = True + break + + next_token_type, next_token_value, *_ = proxy.eat(counter) + if next_token_type == tokenize.OP: + next_token_type = grammar.opmap[cast(str, next_token_value)] + + recorder.add_token(next_token_type, next_token_value) + counter += 1 + + ilabel = cast(int, recorder.determine_route(next_token_value, force=force)) + assert ilabel is not None + + return self._addtoken(ilabel, type, value, context) + + def _addtoken( + self, ilabel: int, type: int, value: Optional[Text], context: Context + ) -> bool: # Loop until the token is shifted; may raise exceptions while True: dfa, state, node = self.stack[-1] @@ -185,20 +293,29 @@ class Parser(object): # No success finding a transition raise ParseError("bad input", type, value, context) - def classify(self, type: int, value: Optional[Text], context: Context) -> int: - """Turn a token into a label. (Internal)""" + def classify(self, type: int, value: Optional[Text], context: Context) -> List[int]: + """Turn a token into a label. (Internal) + + Depending on whether the value is a soft-keyword or not, + this function may return multiple labels to choose from.""" if type == token.NAME: # Keep a listing of all used names assert value is not None self.used_names.add(value) # Check for reserved words - ilabel = self.grammar.keywords.get(value) - if ilabel is not None: - return ilabel + if value in self.grammar.keywords: + return [self.grammar.keywords[value]] + elif value in self.grammar.soft_keywords: + assert type in self.grammar.tokens + return [ + self.grammar.soft_keywords[value], + self.grammar.tokens[type], + ] + ilabel = self.grammar.tokens.get(type) if ilabel is None: raise ParseError("bad token", type, value, context) - return ilabel + return [ilabel] def shift( self, type: int, value: Optional[Text], newstate: int, context: Context