@check_types now properly passes in *args **kwargs and checks their types

[ecthompson99]

Background

• Unexpected behavior of functions with *args or **kwargs when @check_types decorator is applied
• Root cause:
  • validate_inputs() uses sig.bind_partial(*args).arguments which returns an OrderedDict of arguments or keyword arguments. However:
    • *args are bundled into a single value: {arg1: 1, args: (2,3,4)} which is then returned to the wrapped function as (1, (2,3,4)) instead of (1,2,3,4)
    • **kwargs are bundled into a nested dictionary: {kwarg1: 1, kwargs: {kwarg2: 2, kwarg3: 3}} which is then returned to the wrapped function as {kwarg1: 1, {kwargs: {kwarg2: 2, kwarg3: 3}} instead of {kwarg1: 1, kwarg2: 2, kwarg3: 3}

Implementation

All changes added to def check_types (here)

• Additional logic is needed to handle cases when *args or **kwargs are passed in
• Since args and kwargs are treated differently, I split the validate_args into two validation functions -- one for positional arguments, one for keyword arguments
  • def validate_args:
    • Check if there are *args in function arguments by comparing the length of the named arguments (from sig.bind_partial(*args).arguments) and the nominal arguments. If the lengths match, no *args, and handle normally
    • If there are *args, handle the explicit args normally, and then validate each argument in *args, iteratively
    • Combine explicit and star_args into single list to pass into the function
  • def validate_kwargs:
    • Check if there are **kwargs in function arguments by comparing the keys in sig.bind_partial(**kwargs).arguments to the keys in the nominal keyword args. If they are different, then **kwargs exist
    • If there are **kwargs, handle explicit kwargs normally, and then validate each kwarg in **kwargs, iteratively
    • Combine explicit and star_kwargs into single list to pass into the function

Related Issue

#1334

Testing

• Added 3 tests:
  1. test_check_types_star_args: Test for *args by comparing argument lengths
  2. test_check_types_star_kwargs: Test for **kwargs by comparing keys
  3. test_check_types_star_args_kwargs: Test that the values for both *args and **kwargs get passed through correctly

[cosmicBboy]

thanks for the PR! looks like there are some mypy lint errors to address

[ecthompson99]

thanks for the PR! looks like there are some mypy lint errors to address

Hi @cosmicBboy, addressed the mypy and black formatting issues in the most recent commit, thanks!

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (ceeae10) 93.91% compared to head (6b1396e) 94.29%.
Report is 31 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1336      +/-   ##
==========================================
+ Coverage   93.91%   94.29%   +0.37%     
==========================================
  Files          91       91              
  Lines        6775     7024     +249     
==========================================
+ Hits         6363     6623     +260     
+ Misses        412      401      -11     

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[cosmicBboy]

Looks good @ecthompson99 merging now. Congrats on your first PR to pandera!