Merge pull request #982 from lark-parser/astutils_meta

examples/advanced/create_ast.py

@@ -15,6 +15,7 @@ from typing import List
 from dataclasses import dataclass
 
 from lark import Lark, ast_utils, Transformer, v_args
+from lark.tree import Meta
 
 this_module = sys.modules[__name__]
 
@@ -31,7 +32,9 @@ class _Statement(_Ast):
     pass
 
 @dataclass
-class Value(_Ast):
+class Value(_Ast, ast_utils.WithMeta):
+    "Uses WithMeta to include line-number metadata in the meta attribute"
+    meta: Meta
     value: object
 
 @dataclass

lark/ast_utils.py

@@ -19,15 +19,17 @@ class AsList(object):
     Subclasses will be instanciated with the parse results as a single list, instead of as arguments.
     """
 
-def camel_to_snake(name):
-    return re.sub(r'(?<!^)(?=[A-Z])', '_', name).lower()
+class WithMeta(object):
+    """Abstract class
 
-def _call(func, _data, children, _meta):
-    return func(*children)
+    Subclasses will be instanciated with the Meta instance of the tree. (see ``v_args`` for more detail)
+    """
+    pass
 
-inline = v_args(wrapper=_call)
+def camel_to_snake(name):
+    return re.sub(r'(?<!^)(?=[A-Z])', '_', name).lower()
 
-def create_transformer(ast_module, transformer=None):
+def create_transformer(ast_module, transformer=None, decorator_factory=v_args):
     """Collects `Ast` subclasses from the given module, and creates a Lark transformer that builds the AST.
 
     For each class, we create a corresponding rule in the transformer, with a matching name.
@@ -38,15 +40,16 @@ def create_transformer(ast_module, transformer=None):
     Parameters:
         ast_module: A Python module containing all the subclasses of ``ast_utils.Ast``
         transformer (Optional[Transformer]): An initial transformer. Its attributes may be overwritten.
+        decorator_factory (Callable): An optional callable accepting two booleans, inline, and meta, 
+            and returning a decorator for the methods of ``transformer``. (default: ``v_args``).
     """
     t = transformer or Transformer()
 
     for name, obj in inspect.getmembers(ast_module):
         if not name.startswith('_') and inspect.isclass(obj):
             if issubclass(obj, Ast):
-                if not issubclass(obj, AsList):
-                    obj = inline(obj).__get__(t)
-
+                wrapper = decorator_factory(inline=not issubclass(obj, AsList), meta=issubclass(obj, WithMeta))
+                obj = wrapper(obj).__get__(t)
                 setattr(t, camel_to_snake(name), obj)
 
     return t