Validating a dict value agains a Literal type gives the wrong ValidationError

[markus1978]

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

Validating a dict value agains a Literal type gives the wrong ValidationError. Instead of unexpected value; permitted: '*' the validation error just says unhashable type: 'dict' (type=type_error). Which does not describe the problem and is confusing, e.g. if handing this to API users in fastAPI. I would also expect an unexpected value; permitted: '*' for all non string values.

The respective validator in pydantic/validators.py (line 480ff) only catches a KeyError:

def make_literal_validator(type_: Any) -> Callable[[Any], Any]:
    permitted_choices = all_literal_values(type_)

    # To have a O(1) complexity and still return one of the values set inside the `Literal`,
    # we create a dict with the set values (a set causes some problems with the way intersection works).
    # In some cases the set value and checked value can indeed be different (see `test_literal_validator_str_enum`)
    allowed_choices = {v: v for v in permitted_choices}

    def literal_validator(v: Any) -> Any:
        try:
            return allowed_choices[v]
        except KeyError:
            raise errors.WrongConstantError(given=v, permitted=permitted_choices)

    return literal_validator

IMHO, it should also catch a TypeError (i.e. the "unhashable type") and produce a corresponding error. Or, it could check for isinstance(v, str) first and raise respective error if it is not a string.

Example Code

import pydantic
from typing import Literal

pydantic.parse_obj_as(Literal['*'], {})

Python, Pydantic & OS Version

pydantic version: 1.10.9
            pydantic compiled: True
                 install path: ********.pyenv/lib/python3.9/site-packages/pydantic
               python version: 3.9.16 (main, Dec  7 2022, 10:16:11)  [Clang 14.0.0 (clang-1400.0.29.202)]
                     platform: macOS-13.2-x86_64-i386-64bit
     optional deps. installed: ['devtools', 'dotenv', 'email-validator', '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
• Plugins and integration with other tools - mypy, FastAPI, python-devtools, Hypothesis, VS Code, PyCharm, etc.

[hramezani]

Thanks @markus1978 for reporting.

Would you like to open a PR for fixing?

[markus1978]

@hramezani

Would you like to open a PR for fixing?

Sure. I guess, I should base of and target 1.10.X-fixes?

[hramezani]

@hramezani

Would you like to open a PR for fixing?

Sure. I guess, I should base of and target 1.10.X-fixes?

Yes

[hramezani]

Fixed in d7afe99