Allow install under pypy (#2559)

[etc/vim.git] / src / blib2to3 / pgen2 / parse.py

diff --git a/src/blib2to3/pgen2/parse.py b/src/blib2to3/pgen2/parse.py
index 47c8f02b4f5c8ee081ed70f4ba26f351483095a0..dc405264bad454a92469cb613b6dd962c394e837 100644 (file)
--- 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.
 
 """
 how this parsing engine works.
 
 """

+import copy
+from contextlib import contextmanager

 
 # Local imports
 
 # Local imports

-from . import token
+from . import grammar, token, tokenize

 from typing import (
 from typing import (

+    cast,
+    Any,

     Optional,
     Text,
     Union,
     Tuple,
     Dict,
     List,
     Optional,
     Text,
     Union,
     Tuple,
     Dict,
     List,

+    Iterator,

     Callable,
     Set,
     Callable,
     Set,

+    TYPE_CHECKING,

 )
 from blib2to3.pgen2.grammar import Grammar
 from blib2to3.pytree import NL, Context, RawNode, Leaf, Node
 
 )
 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]]
 
 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])
 
 
     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."""
 
 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
 
         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.
         """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.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
 
     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]
         # 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)
 
                     # 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
         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)
         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
 
     def shift(
         self, type: int, value: Optional[Text], newstate: int, context: Context