]> git.madduck.net Git - etc/vim.git/blobdiff - src/blib2to3/pgen2/parse.py

madduck's git repository

Every one of the projects in this repository is available at the canonical URL git://git.madduck.net/madduck/pub/<projectpath> — see each project's metadata for the exact URL.

All patches and comments are welcome. Please squash your changes to logical commits before using git-format-patch and git-send-email to patches@git.madduck.net. If you'd read over the Git project's submission guidelines and adhered to them, I'd be especially grateful.

SSH access, as well as push access can be individually arranged.

If you use my repositories frequently, consider adding the following snippet to ~/.gitconfig and using the third clone URL listed for each project:

[url "git://git.madduck.net/madduck/"]
  insteadOf = madduck:

Bump docker/build-push-action from 2 to 3 (#3057)
[etc/vim.git] / src / blib2to3 / pgen2 / parse.py
index 792e8e66698246f578fef7ce88d7bf69258af3e9..a9dc11f39ce15deedbcb57cbef8d5774c238d4ea 100644 (file)
@@ -46,6 +46,17 @@ 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
@@ -53,8 +64,8 @@ class Recorder:
         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}
+        self._start_point = self.parser.stack
+        self._points = {ilabel: stack_copy(self._start_point) for ilabel in ilabels}
 
     @property
     def ilabels(self) -> Set[int]:
@@ -62,13 +73,32 @@ class Recorder:
 
     @contextmanager
     def switch_to(self, ilabel: int) -> Iterator[None]:
-        self.parser.stack = self._points[ilabel]
+        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
-        except ParseError:
-            self._dead_ilabels.add(ilabel)
         finally:
-            self.parser.stack = self._start_point
+            self.parser.is_backtracking = is_backtracking
 
     def add_token(self, tok_type: int, tok_val: Text, raw: bool = False) -> None:
         func: Callable[..., Any]
@@ -179,6 +209,7 @@ 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, proxy: "TokenProxy", start: Optional[int] = None) -> None:
         """Prepare for parsing.
@@ -238,6 +269,10 @@ class Parser(object):
                     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]
 
@@ -319,28 +354,40 @@ class Parser(object):
 
     def shift(self, type: int, value: Text, newstate: int, context: Context) -> None:
         """Shift a token.  (Internal)"""
-        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)
+        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)
 
     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 = convert(self.grammar, popnode)
-        if self.stack:
-            dfa, state, node = self.stack[-1]
-            assert node[-1] is not None
-            node[-1].append(newnode)
+        if self.is_backtracking:
+            self.stack.pop()
         else:
-            self.rootnode = newnode
-            self.rootnode.used_names = self.used_names
+            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
+                node[-1].append(newnode)
+            else:
+                self.rootnode = newnode
+                self.rootnode.used_names = self.used_names