add

ccxt/static_dependencies/lark/ast_utils.py

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+"""
+    Module of utilities for transforming a lark.Tree into a custom Abstract Syntax Tree (AST defined in classes)
+"""
+
+import inspect, re
+import types
+from typing import Optional, Callable
+
+from lark import Transformer, v_args
+
+class Ast:
+    """Abstract class
+
+    Subclasses will be collected by `create_transformer()`
+    """
+    pass
+
+class AsList:
+    """Abstract class
+
+    Subclasses will be instantiated with the parse results as a single list, instead of as arguments.
+    """
+
+class WithMeta:
+    """Abstract class
+
+    Subclasses will be instantiated with 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 create_transformer(ast_module: types.ModuleType,
+                       transformer: Optional[Transformer]=None,
+                       decorator_factory: Callable=v_args) -> Transformer:
+    """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.
+    CamelCase names will be converted into snake_case. Example: "CodeBlock" -> "code_block".
+
+    Classes starting with an underscore (`_`) will be skipped.
+
+    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):
+                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