Add `nodes.Const.kind` for `r` prefix and Python < 3.8

[DanielNoord]

Current behavior

Following discussion in pylint-dev/pylint#4787 additional functionality for the nodes.Const.kind attribute would be helpful.
See documentation for current behaviour, which only supports the u prefix and Python =< 3.8

Expected behavior

For the following code, inferring a_string and checking its kind should return r.

Note: at the same time making kind work with the f prefix or combined prefixes such as fr might be possible

a_string = r"Test string"

[Pierre-Sassoulas]

Thank you for creating the issue :)

[cdce8p]

Unfortunately, I don't think this is possible at the moment. The Const.kind value is extracted from the Constant ast node. That is only ever u or None.

import ast
import sys

code = """
a_string = r"Test string"
"""

if __name__ == '__main__':
    ast_node = ast.parse(code)
    if sys.version_info >= (3, 9):
        print(ast.dump(ast_node, indent=2))
    else:
        print(ast.dump(ast_node))

--
python/cpython#12295
https://bugs.python.org/issue36280
#943

[DanielNoord]

I was thinking of looking for the column number of the string and doing columnno - 1 to look for the prefix and handle some edge cases. Is this something worth trying, or do you foresee problems which such a basic approach?

[cdce8p]

I was thinking of looking for the column number of the string and doing columnno - 1 to look for the prefix and handle some edge cases. Is this something worth trying, or do you foresee problems which such a basic approach?

It might work although there might be issues to be aware of. Just to name one: The Const node can contain not just strings, but bytes, ints, bool, None, ... as well. I would need to investigate it further at some point.

If you like, you can take a look at it yourself. The logic should probably be part of nodes.Const.__init__(...).