Exception parsing negative integer strings

[noamkush]

Initial Checks

• I confirm that I'm using Pydantic V2

Description

Starting with pydantic 2.7.1 parsing an integer string like '-1.0' gives an error while '1.0' works fine. Probably related to pydantic/pydantic-core#1269 or pydantic/pydantic-core#1272.

Example Code

In [1]: import pydantic

In [2]: class A(pydantic.BaseModel):
   ...:     i: int
   ...: 

In [3]: A(i='4.0')
Out[3]: A(i=4)

In [4]: A(i='-4.0')
---------------------------------------------------------------------------
ValidationError                           Traceback (most recent call last)
Cell In[4], line 1
----> 1 A(i='-4.0')

File ~/.cache/pypoetry/virtualenvs/hl-7m4wOqun-py3.12/lib/python3.12/site-packages/pydantic/main.py:176, in BaseModel.__init__(self, **data)
    174 # `__tracebackhide__` tells pytest and some other tools to omit this function from tracebacks
    175 __tracebackhide__ = True
--> 176 self.__pydantic_validator__.validate_python(data, self_instance=self)

ValidationError: 1 validation error for A
i
  Input should be a valid integer, unable to parse string as an integer [type=int_parsing, input_value='-4.0', input_type=str]
    For further information visit https://errors.pydantic.dev/2.7/v/int_parsing

Python, Pydantic & OS Version

             pydantic version: 2.7.1
        pydantic-core version: 2.18.2
          pydantic-core build: profile=release pgo=true
                 install path: /home/noam/.cache/pypoetry/virtualenvs/hl-7m4wOqun-py3.12/lib/python3.12/site-packages/pydantic
               python version: 3.12.3 (main, Apr 10 2024, 05:33:47) [GCC 13.2.0]
                     platform: Linux-5.15.133.1-microsoft-standard-WSL2-x86_64-with-glibc2.39
             related packages: typing_extensions-4.10.0 mypy-1.7.1
                       commit: unknown

[RajatRajdeep]

I investigated this and the issue seems to be in strip_leading_zeros function where if any character occurs except (+, _, 1 ... 9) in the string then None is being returned. The - character is not handled here and due to this it's throwing validation error.

https://github.com/pydantic/pydantic-core/blob/main/src/input/shared.rs#L149-L168

[sydney-runkle]

Hey folks,

Thanks for reporting this bug. Definitely something we want to fix in 2.7.2. Should be an easy fix if anyone is interested in contributing to pydantic-core. I'll pick this up soon if not!

[RajatRajdeep]

I'll pick it up.