make parser yield trees only at the end in one step

Author: alex9849

src/fandango/language/grammar/parser/forest.py

@@ -163,22 +163,22 @@ def open_frame(target: ParseState) -> None:
                 self._children_keepalive.append(frame.state)
         return resolve(state)
 
-    def all_children_of(self, state: ParseState) -> Iterator[DerivationTree]:
+    def derivations_of(self, state: ParseState) -> Iterator[DerivationTree]:
         """
-        The children of `state` in every derivation, the first derivation first.
+        The trees for all derivations of `state` on-demand.
         """
-        choices = _Choices([])
-        yield from self.children_of(state, choices)
-        picks = [0] * len(choices.edge_counts)
+        picks: list[int] = []
         while True:
+            choices = _Choices(picks)
+            # Returns a list with exactly one element. We take it.
+            (tree,) = self.children_of(state, choices)
+            yield tree
+            picks += [0] * (len(choices.edge_counts) - len(picks))
             while picks and picks[-1] + 1 == choices.edge_counts[len(picks) - 1]:
                 picks.pop()
             if not picks:
                 return
             picks[-1] += 1
-            choices = _Choices(picks)
-            yield from self.children_of(state, choices)
-            picks += [0] * (len(choices.edge_counts) - len(picks))
 
     def _is_ambiguous(self, state: ParseState) -> bool:
         """

src/fandango/language/grammar/parser/iterative_parser.py

@@ -499,8 +499,8 @@ def tree_at(self, offset: int) -> Generator[DerivationTree, None, None]:
         state = self._completed.get(offset)
         if state is None:
             return
-        for child in self._forest.all_children_of(state):
-            yield self.to_derivation_tree(child)
+        for tree in self._forest.derivations_of(state):
+            yield self.to_derivation_tree(tree)
 
     def _consume(
         self, char: str | bytes | int, *, build_trees: bool = True
@@ -594,12 +594,12 @@ def _consume(
 
             if build_trees:
                 for state in starts_to_yield:
-                    for child in self._forest.all_children_of(state):
+                    for tree in self._forest.derivations_of(state):
                         if self._parsing_mode == ParsingMode.INCOMPLETE:
-                            if child in self._yielded_incomplete:
+                            if tree in self._yielded_incomplete:
                                 continue
-                            self._yielded_incomplete.add(child)
-                        yield child, state.is_finished
+                            self._yielded_incomplete.add(tree)
+                        yield tree, state.is_finished
 
             column_index += 1
             if column_index % columns_per_byte == 0: