X-Git-Url: https://git.madduck.net/etc/vim.git/blobdiff_plain/2082a325fdd14f0aabd88f7f12a20f9fb085c538..0b4d7d55f78913be9e0a3738681ef3aafd5d9a5a:/src/blib2to3/pgen2/parse.py?ds=sidebyside diff --git a/src/blib2to3/pgen2/parse.py b/src/blib2to3/pgen2/parse.py index 8c374d3..17bf118 100644 --- a/src/blib2to3/pgen2/parse.py +++ b/src/blib2to3/pgen2/parse.py @@ -9,26 +9,31 @@ See Parser/parser.c in the Python distribution for additional info on how this parsing engine works. """ +from contextlib import contextmanager # Local imports -from . import token +from . import grammar, token, tokenize from typing import ( - Optional, - Text, - Sequence, + cast, Any, + Optional, Union, Tuple, Dict, List, + Iterator, Callable, Set, + TYPE_CHECKING, ) from blib2to3.pgen2.grammar import Grammar -from blib2to3.pytree import NL, Context, RawNode, Leaf, Node +from blib2to3.pytree import convert, NL, Context, RawNode, Leaf, Node + +if TYPE_CHECKING: + from blib2to3.pgen2.driver import TokenProxy -Results = Dict[Text, NL] +Results = Dict[str, NL] Convert = Callable[[Grammar, RawNode], Union[Node, Leaf]] DFA = List[List[Tuple[int, int]]] DFAS = Tuple[DFA, Dict[int, int]] @@ -39,14 +44,95 @@ def lam_sub(grammar: Grammar, node: RawNode) -> NL: return Node(type=node[0], children=node[3], context=node[2]) +# A placeholder node, used when parser is backtracking. +DUMMY_NODE = (-1, None, None, None) + + +def stack_copy( + stack: List[Tuple[DFAS, int, RawNode]] +) -> List[Tuple[DFAS, int, RawNode]]: + """Nodeless stack copy.""" + return [(dfa, label, DUMMY_NODE) for dfa, label, _ in stack] + + +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 = self.parser.stack + self._points = {ilabel: stack_copy(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]: + with self.backtrack(): + self.parser.stack = self._points[ilabel] + try: + yield + except ParseError: + self._dead_ilabels.add(ilabel) + finally: + self.parser.stack = self._start_point + + @contextmanager + def backtrack(self) -> Iterator[None]: + """ + Use the node-level invariant ones for basic parsing operations (push/pop/shift). + These still will operate on the stack; but they won't create any new nodes, or + modify the contents of any other existing nodes. + + This saves us a ton of time when we are backtracking, since we + want to restore to the initial state as quick as possible, which + can only be done by having as little mutatations as possible. + """ + is_backtracking = self.parser.is_backtracking + try: + self.parser.is_backtracking = True + yield + finally: + self.parser.is_backtracking = is_backtracking + + def add_token(self, tok_type: int, tok_val: str, 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[str] = 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.""" def __init__( - self, msg: Text, type: Optional[int], value: Optional[Text], context: Context + self, msg: str, type: Optional[int], value: Optional[str], context: Context ) -> None: Exception.__init__( - self, "%s: type=%r, value=%r, context=%r" % (msg, type, value, context) + self, f"{msg}: type={type!r}, value={value!r}, context={context!r}" ) self.msg = msg self.type = type @@ -54,7 +140,7 @@ class ParseError(Exception): self.context = context -class Parser(object): +class Parser: """Parser engine. The proper usage sequence is: @@ -102,6 +188,11 @@ class Parser(object): to be converted. The syntax tree is converted from the bottom up. + **post-note: the convert argument is ignored since for Black's + usage, convert will always be blib2to3.pytree.convert. Allowing + this to be dynamic hurts mypyc's ability to use early binding. + These docs are left for historical and informational value. + A concrete syntax tree node is a (type, value, context, nodes) tuple, where type is the node type (a token or symbol number), value is None for symbols and a string for tokens, context is @@ -114,9 +205,11 @@ class Parser(object): """ self.grammar = grammar + # See note in docstring above. TL;DR this is ignored. self.convert = convert or lam_sub + self.is_backtracking = False - 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. @@ -139,11 +232,57 @@ 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: + def addtoken(self, type: int, value: str, 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 in (tokenize.COMMENT, tokenize.NL): + counter += 1 + continue + + if next_token_type == tokenize.OP: + next_token_type = grammar.opmap[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: str, context: Context) -> bool: # Loop until the token is shifted; may raise exceptions while True: dfa, state, node = self.stack[-1] @@ -151,10 +290,18 @@ class Parser(object): arcs = states[state] # Look for a state with this label for i, newstate in arcs: - t, v = self.grammar.labels[i] - if ilabel == i: + t = self.grammar.labels[i][0] + if t >= 256: + # See if it's a symbol and if we're in its first set + itsdfa = self.grammar.dfas[t] + itsstates, itsfirst = itsdfa + if ilabel in itsfirst: + # Push a symbol + self.push(t, itsdfa, newstate, context) + break # To continue the outer while loop + + elif ilabel == i: # Look it up in the list of labels - assert t < 256 # Shift a token; we're done with it self.shift(type, value, newstate, context) # Pop while we are in an accept-only state @@ -168,14 +315,7 @@ class Parser(object): states, first = dfa # Done with this token return False - elif t >= 256: - # See if it's a symbol and if we're in its first set - itsdfa = self.grammar.dfas[t] - itsstates, itsfirst = itsdfa - if ilabel in itsfirst: - # Push a symbol - self.push(t, self.grammar.dfas[t], newstate, context) - break # To continue the outer while loop + else: if (0, state) in arcs: # An accepting state, pop it and try something else @@ -187,47 +327,61 @@ 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: str, 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 - ) -> None: + def shift(self, type: int, value: str, newstate: int, context: Context) -> None: """Shift a token. (Internal)""" - dfa, state, node = self.stack[-1] - assert value is not None - assert context is not None - rawnode: RawNode = (type, value, context, None) - newnode = self.convert(self.grammar, rawnode) - if newnode is not None: + if self.is_backtracking: + dfa, state, _ = self.stack[-1] + self.stack[-1] = (dfa, newstate, DUMMY_NODE) + else: + dfa, state, node = self.stack[-1] + rawnode: RawNode = (type, value, context, None) + newnode = convert(self.grammar, rawnode) assert node[-1] is not None node[-1].append(newnode) - self.stack[-1] = (dfa, newstate, node) + self.stack[-1] = (dfa, newstate, node) def push(self, type: int, newdfa: DFAS, newstate: int, context: Context) -> None: """Push a nonterminal. (Internal)""" - dfa, state, node = self.stack[-1] - newnode: RawNode = (type, None, context, []) - self.stack[-1] = (dfa, newstate, node) - self.stack.append((newdfa, 0, newnode)) + if self.is_backtracking: + dfa, state, _ = self.stack[-1] + self.stack[-1] = (dfa, newstate, DUMMY_NODE) + self.stack.append((newdfa, 0, DUMMY_NODE)) + else: + dfa, state, node = self.stack[-1] + newnode: RawNode = (type, None, context, []) + self.stack[-1] = (dfa, newstate, node) + self.stack.append((newdfa, 0, newnode)) def pop(self) -> None: """Pop a nonterminal. (Internal)""" - popdfa, popstate, popnode = self.stack.pop() - newnode = self.convert(self.grammar, popnode) - if newnode is not None: + if self.is_backtracking: + self.stack.pop() + else: + popdfa, popstate, popnode = self.stack.pop() + newnode = convert(self.grammar, popnode) if self.stack: dfa, state, node = self.stack[-1] assert node[-1] is not None