Merge pull request #1467 from makukha/1466-add-tree-find-token

Add Tree.find_token() method

.gitignore

@@ -1,6 +1,7 @@
 *.pyc
 *.pyo
 /.tox
+/lark.egg-info/**
 /lark_parser.egg-info/**
 tags
 .vscode

lark/tree.py

@@ -3,8 +3,10 @@
 
 from typing import List, Callable, Iterator, Union, Optional, Generic, TypeVar, TYPE_CHECKING
 
+from .lexer import Token
+
 if TYPE_CHECKING:
-    from .lexer import TerminalDef, Token
+    from .lexer import TerminalDef
     try:
         import rich
     except ImportError:
@@ -171,6 +173,16 @@ def find_data(self, data: str) -> 'Iterator[Tree[_Leaf_T]]':
 
 ###}
 
+    def find_token(self, token_type: str) -> Iterator[_Leaf_T]:
+        """Returns all tokens whose type equals the given token_type.
+
+        This is a recursive function that will find tokens in all the subtrees.
+
+        Example:
+            >>> term_tokens = tree.find_token('TERM')
+        """
+        return self.scan_values(lambda v: isinstance(v, Token) and v.type == token_type)
+
     def expand_kids_by_data(self, *data_values):
         """Expand (inline) children with any of the given data values. Returns True if anything changed"""
         changed = False

tests/test_trees.py

@@ -17,6 +17,11 @@
 class TestTrees(TestCase):
     def setUp(self):
         self.tree1 = Tree('a', [Tree(x, y) for x, y in zip('bcd', 'xyz')])
+        self.tree2 = Tree('a', [
+            Tree('b', [Token('T', 'x')]),
+            Tree('c', [Token('T', 'y')]),
+            Tree('d', [Tree('z', [Token('T', 'zz'), Tree('zzz', 'zzz')])]),
+        ])
 
     def test_eq(self):
         assert self.tree1 == self.tree1
@@ -48,6 +53,11 @@ def test_iter_subtrees_topdown(self):
         nodes = list(self.tree1.iter_subtrees_topdown())
         self.assertEqual(nodes, expected)
 
+    def test_find_token(self):
+        expected = [Token('T', 'x'), Token('T', 'y'), Token('T', 'zz')]
+        tokens = list(self.tree2.find_token('T'))
+        self.assertEqual(tokens, expected)
+
     def test_visitor(self):
         class Visitor1(Visitor):
             def __init__(self):