[BUG] LibCST.RemoveFromParent() function removes extra lines!!!

[hadialqattan]

These codes should remove only from .pgen2 import token import statement, but actually it removes two additional lines!

from typing import Union

import libcst as cst


class Transformer(cst.CSTTransformer):
    def leave_ImportFrom(
        self, original_node: cst.ImportFrom, updated_node: cst.ImportFrom
    ) -> Union[cst.RemovalSentinel, cst.ImportFrom]:
        if updated_node.names[0].name.value == "token":  # Hard coded name to remove.
            return cst.RemoveFromParent()  # Here we have a bug!
        return updated_node


def refactor_string(source: str) -> str:
    cst_tree = cst.parse_module(source)
    return cst_tree.visit(Transformer()).code


if __name__ == "__main__":
    refactored_code = refactor_string(
        """# Python imports
import os

from typing import Union

# Local imports
from .pgen2 import token
from .pgen2 import driver

from .pgen2.grammar import Grammar

os, Union, driver, Grammar"""
    )
    print(refactored_code)

Expected output:

# Python imports
 import os

 from typing import Union

# Local imports
-from .pgen2 import token
 from .pgen2 import driver

 from .pgen2.grammar import Grammar

os, Union, driver, Grammar

Actual output

# Python imports
 import os

 from typing import Union
-
-# Local imports
-from .pgen2 import token
 from .pgen2 import driver

 from .pgen2.grammar import Grammar
os, Union, driver, Grammar

[thatch]

The representation that LibCST uses for comments and whitespace is to attach them to some node. In this case, you wanted to keep the comments, but removed the node that owned them, which is why they went away. I have a similar use case where I reorder nodes, and see the comments move (in a somewhat arbitrary-looking, but at least consistent, way).

Did you expect LibCST to move those to another node for you?

[hadialqattan]

The representation that LibCST uses for comments and whitespace is to attach them to some node. In this case, you wanted to keep the comments, but removed the node that owned them, which is why they went away. I have a similar use case where I reorder nodes, and see the comments move (in a somewhat arbitrary-looking, but at least consistent, way).

Did you expect LibCST to move those to another node for you?

Clear, thank you!