ast_utils: Refactor and improve interface

examples/advanced/create_ast.py

@@ -31,7 +31,8 @@ class _Statement(_Ast):
     pass
 
 @dataclass
-class Value(_Ast):
+class Value(_Ast, ast_utils.WithMeta):
+    meta: object
     value: object
 
 @dataclass

lark/ast_utils.py

@@ -20,23 +20,16 @@ class AsList(object):
     """
 
 class WithMeta(object):
+    """Abstract class
+
+    Subclasses will be instanciated the Meta instance of the tree. (see ``v_args`` for more detail)
+    """
     pass
 
 def camel_to_snake(name):
     return re.sub(r'(?<!^)(?=[A-Z])', '_', name).lower()
 
-def _call(func, _data, children, _meta):
-    return func(*children)
-def _call_with_meta(func, _data, children, meta):
-    return func(meta, children)
-def _call_with_meta_inline(func, _data, children, meta):
-    return func(meta, *children)
-
-inline = v_args(wrapper=_call)
-with_meta = v_args(wrapper=_call_with_meta)
-with_meta_inline = v_args(wrapper=_call_with_meta_inline)
-
-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.
@@ -47,20 +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):
-                    if issubclass(obj, WithMeta):
-                        obj = with_meta_inline(obj).__get__(t)
-                    else:
-                        obj = inline(obj).__get__(t)
-                elif issubclass(obj, WithMeta):
-                    obj = with_meta(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