Feature: allows ast subscript

[lucasiscovici2]

Hello, and thank you for dev Darglint 🙂 This Pr is intended to allow more complicated types hints to be detected for parameters and return. (With "[") Ex: List[int], Union[int, str], ....

TODO :

• [x] parameters
• [ ] tests
• [ ] return
• [ ] doc
• [ ] change the display depending on the version of python

Explanation :

• Using ast.dump to transform type hints annotations (ast.AST) into strings..
• Using ast.parse to transform doctring (string) into ast.AST and using ast.dump to transform into string

Why ast.parse/ast.dump ?

• Because is compatible with python 2 & 3
• Python Standard Library

Pb ?

• Not clear error message for "ParameterTypeMismatchError" : "actual" is a string but "excepted“ is the ast.dump of the ast.AST

Alternatives :

• change solution according to the python version
  • Python 3.9 : ast.unparse
  • Python 3.8 : ast.get_source_segment
  • Less Python 3.8 : ast.dump and ast.parse
• use others libraries
  • astunparse
  • astmonkey

Even if it's a draft, I would like your corrections/comments ✍🏻 🙂

Ex: test.py

def fib(self, a: List[int], b: int) -> List[int]:
        """Fibo.

        Parameters
        ----------
        a : List[str]
            the first number
        b : int
            the second number

        Returns
        -------
        List[int]
            the fibo resut
        """
        return a

original_darglint test.py  // no error
darglint test.py  // test.py:fib:0: DAR103:  ~a: expected Subscript(Name('List', Load()), Name('int', Load()), Load()) but was List[str]

[terrencepreilly]

Could you explain what problem this PR is solving? How is doing analysis on the function's type signature helpful? Ideally, an explanation for why this is useful would include examples, a brief cost-benefit analysis (e.g. how difficult would this change be to maintain), and an explanation of alternative solutions.

[lucasiscovici2]

Could you explain what problem this PR is solving? How is doing analysis on the function's type signature helpful? Ideally, an explanation for why this is useful would include examples, a brief cost-benefit analysis (e.g. how difficult would this change be to maintain), and an explanation of alternative solutions.

@terrencepreilly https://github.com/terrencepreilly/darglint/pull/194#issue-1106148726

[lucasiscovici2]

@terrencepreilly maybe the best is to use astunparse (Until python 3.8) and ast.unparse (From python 3.9) ?

[lucasiscovici2]

@terrencepreilly maybe the best is to use astunparse (Until python 3.8) and ast.unparse (From python 3.9) ?

@terrencepreilly i create the pr #195 for this solution 🙂