`StrictBytes` does not raise `ValidationError` when `max_length` is present in `Field`

[arthurazs]

Initial Checks

• I have searched GitHub for a duplicate issue and I'm sure this is something new
• I have searched Google & StackOverflow for a solution and couldn't find anything
• I have read and followed the docs and still think this is a bug
• I am confident that the issue is with pydantic (not my code, or another library in the ecosystem like FastAPI or mypy)

Description

I'm using pydantic version 1.9.2.

Mind this model:

# my_model/__init__.py
from pydantic import BaseModel, StrictBytes, Field


class Model(BaseModel):
    a: StrictBytes = Field(...)
    b: StrictBytes = Field(..., max_length=5)

Even though b is StrictBytes, I can create an object with the following line:

m = Model(a=b'arthur', b=123) which I assume is a bug.

I cannot create an object the other way around:
m = Model(a=123, b=b'art'), which I assume is the intended behaviour.

---

Here follows a pytest example:

# tests/test_my_model.py

from my_model import Model
import pytest
from pydantic import ValidationError


def test_normal():
    m = Model(a=b'arthur', b=b'lucas')
    assert m.a == b'arthur'
    assert m.b == b'lucas'

def test_large():
    with pytest.raises(ValidationError) as error:
        m = Model(a=b'arthur', b=b'arthur')
    assert 'b\n' in str(error.value)
    assert 'value_error.any_str.max_length' in str(error.value)

def test_a_str():
    with pytest.raises(ValidationError) as error:
        m = Model(a=123123, b=b'lucas')
    assert 'a\n' in str(error.value)
    assert 'type_error.bytes' in str(error.value)

def test_b_str():
    with pytest.raises(ValidationError) as error:
        m = Model(a=b'arthur', b=123)  # does not raise
    assert 'b\n' in str(error.value)
    assert 'type_error.bytes' in str(error.value)

And the output from pytest:

platform linux -- Python 3.10.6, pytest-6.2.5, py-1.11.0, pluggy-1.0.0
rootdir: /home/arthurazs/Desktop/my_model
collected 4 items                                                                     

tests/test_my_model.py ...F                                                      [100%]

====================================== FAILURES =======================================
_____________________________________ test_b_str ______________________________________

    def test_b_str():
>       with pytest.raises(ValidationError) as error:
E       Failed: DID NOT RAISE <class 'pydantic.error_wrappers.ValidationError'>

tests/test_my_model.py:24: Failed
=============================== short test summary info ===============================
FAILED tests/test_my_model.py::test_b_str - Failed: DID NOT RAISE <class 'pydantic.e...
============================= 1 failed, 3 passed in 0.04s =============================

Example Code

from pydantic import BaseModel, StrictBytes, Field


class Model(BaseModel):
    a: StrictBytes = Field(...)
    b: StrictBytes = Field(..., max_length=5)

m = Model(a=b'arthur', b=123)  # does not raise

Python, Pydantic & OS Version

pydantic version: 1.9.2
            pydantic compiled: True
                 install path: /home/arthurazs/.cache/pypoetry/virtualenvs/asd-8JLwExQw-py3.10/lib/python3.10/site-packages/pydantic
               python version: 3.10.6 (main, Aug  2 2022, 15:11:28) [GCC 9.4.0]
                     platform: Linux-5.15.0-46-generic-x86_64-with-glibc2.31
     optional deps. installed: ['typing-extensions']

Affected Components

• Compatibility between releases
• Data validation/parsing
• Data serialization - .dict() and .json()
• JSON Schema
• Dataclasses
• Model Config
• Field Types - adding or changing a particular data type
• Function validation decorator
• Generic Models
• Other Model behaviour - construct(), pickling, private attributes, ORM mode
• Settings Management
• Plugins and integration with other tools - mypy, FastAPI, python-devtools, Hypothesis, VS Code, PyCharm, etc.

[hramezani]

The reason is, by setting the max_length in b (b: StrictBytes = Field(..., max_length=5)), it won't be considered as StrictBytes anymore. then the provided value 123 will be converted to bytes during validation

from pydantic import BaseModel, StrictBytes, Field


class Model(BaseModel):
    a: StrictBytes = Field(...)
    b: StrictBytes = Field(..., max_length=5)

m = Model(a=b'arthur', b=123)  # does not raise
print(m)  # a=b'arthur' b=b'123'

I am not sure if is it an intended behavior or not. @samuelcolvin what is your opinion here?

[samuelcolvin]

It's an error, happy to review a PR if it's simple and submitted asap. Otherwise this is/will be fixed in V2.