feat: add attribute exclusion mecanism

[zephvr]

Hi
I would like to propose this PR to fulfill #75 request

Sadly attributes cannot be decorated, so I introduce a new syntax that allow an attribute to be ignore.
Simply commenting # tap: ignore will ignore the attribute

With it this code

# code.py
from typing import ClassVar
from tap import Tap

class Args(Tap):
    attr_to_ignore: str  # tap: ignore
    """A comment for my IDE"""
    classvar_attr: ClassVar[str]
    hello: bool = True

args = Args().parse_args()

Gives

$ python code.py -h
usage: code.py [--hello] [-h]

options:
  --hello     (bool, default=True)
  -h, --help  show this help message and exit

Tell me if there is anything I can improve on this PR 😄

[martinjm97]

Hey @zephvr,

Thank you so much for the PR and sorry for the massive delay in response. We really like the overall setup. In general, we don't want the behavior of the Tap object to change based on comments, so we'd argue against # tap: ignore. We also think because ClassVar is not extremely well known, it could be confusing to users for that argument not to show up in the parsed object. One option is to have a thin wrapper around ClassVar called TapIgnore.

We're imagining something that looks like:

# code.py
from tap import Tap, TapIgnore

class Args(Tap):
    """A comment for my IDE"""
    attr_to_ignore: TapIgnore[str]
    classvar_attr: TapIgnore[str]
    hello: bool = True

args = Args().parse_args()

We would appreciate if you could make these changes, but ideally, we'll do it eventually.

Thanks,
Jesse and Kyle

[rainyl]

Well, I do like this feature, any progress?