Add Positional Feature

[Daraan]

Resolves: #169

To also work for pydantic needs: #174, then also resolves: #165 (thats why latest tests) fail

Supports

from tap import Tap, Positional

class MyTap(Tap):
    positional_arg: Positional[int]
    positional_default: Positional[int] = 2
    positional_args: Positional[list[str]]

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.38%. Comparing base (2215ef5) to head (7199f92).
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Additional details and impacted files

@@            Coverage Diff             @@
##             main     #176      +/-   ##
==========================================
+ Coverage   94.18%   94.38%   +0.20%     
==========================================
  Files           4        4              
  Lines         757      784      +27     
==========================================
+ Hits          713      740      +27     
  Misses         44       44              

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[Daraan]

This avoids just an additional untrimmed space at the end of the help message if there is none; i.e. "(int, required) " -> "(int, required)"

[Daraan]

Ready for review :)

[martinjm97]

Thank you! This looks great! Sorry for the delay, we'll do our best to review this sizable PR soon.

--JK

[Daraan]

Tell me if you think something needs a redesign.

[swansonk14]

Hi @Daraan,

Thank you so much for this PR! Overall it looks great! One issue we noticed is a mismatch in behavior between argparse and Tap in the way that the order of positionals with defaults is handled. We will work on fixing it in the next few hours. We also left a few other comments regarding additional tests and documentation that we will work on.

--JK

[swansonk14]

We agree that this is correct behavior for PositionalOptionalOrder1, but we think that this is incorrect for PositionalOptionalOrder3. In PositionalOptionalOrder3, since barg is the first positional, the input "custom" should map to barg even though barg has a default value, which would then lead to a crash. This happens in argparse as seen in the code below.

from argparse import ArgumentParser

parser = ArgumentParser()
parser.add_argument("barg", type=int, default=1)
parser.add_argument("arg", type=str)

args = parser.parse_args(["custom"])

which produces the error

usage: main.py [-h] barg arg
main.py: error: argument barg: invalid int value: 'custom'

We would suggest changing this test so that PositionalOptionalOrder1 runs this code but PositionalOptionalOrder3 expects a SystemExit.

[swansonk14]

These tests are great, but it might be worth adding at least one more complex test with multiple positional and non-positional arguments.

[swansonk14]

It would also be good to include a test that passes an argument to the function directly (via **func_kwargs in tapify) rather than through the CLI. For example,

def greet(name: Positional[str], age: int):
    return f"Hello, {name} ({age})!"


output = tapify(greet, command_line_args=["Alice"], age=32)

[swansonk14]

Show example usage.

"""main.py"""
from tap import Tap, Positional

class MyTap(Tap):
    required_arg: str
    default_arg: str = 'default value'
    positional_arg: Positional[int]

args = MyTap().parse_args()
print(f"positional = {args.positional_arg}, required = {args.required_arg}, default = {args.default_arg}")

For example, running

>>> python main.py 42 --required_arg "I'm required"

would produce

positional = 42, required = "I'm required", default = "default value"

[martinjm97]

We believe we have the few minor fixes completed. We'll merge and then apply those fixes. Thank you again and sorry for the delay on the merge!

--JK