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# Copyright (c) Meta Platforms, Inc. and affiliates.
#
# This source code is licensed under the MIT license found in the
# LICENSE file in the root directory of this source tree.
import re
from typing import Dict, Pattern, Union
import libcst as cst
from libcst.codemod._context import CodemodContext
from libcst.codemod._visitor import ContextAwareVisitor
from libcst.metadata import PositionProvider
class GatherCommentsVisitor(ContextAwareVisitor):
"""
Collects all comments matching a certain regex and their line numbers.
This visitor is useful for capturing special-purpose comments, for example
``noqa`` style lint suppression annotations.
Standalone comments are assumed to affect the line following them, and
inline ones are recorded with the line they are on.
After visiting a CST, matching comments are collected in the ``comments``
attribute.
"""
METADATA_DEPENDENCIES = (PositionProvider,)
def __init__(self, context: CodemodContext, comment_regex: str) -> None:
super().__init__(context)
#: Dictionary of comments found in the CST. Keys are line numbers,
#: values are comment nodes.
self.comments: Dict[int, cst.Comment] = {}
self._comment_matcher: Pattern[str] = re.compile(comment_regex)
def visit_EmptyLine(self, node: cst.EmptyLine) -> bool:
if node.comment is not None:
self.handle_comment(node)
return False
def visit_TrailingWhitespace(self, node: cst.TrailingWhitespace) -> bool:
if node.comment is not None:
self.handle_comment(node)
return False
def handle_comment(
self, node: Union[cst.EmptyLine, cst.TrailingWhitespace]
) -> None:
comment = node.comment
assert comment is not None # ensured by callsites above
if not self._comment_matcher.match(comment.value):
return
line = self.get_metadata(PositionProvider, comment).start.line
if isinstance(node, cst.EmptyLine):
# Standalone comments refer to the next line
line += 1
self.comments[line] = comment
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