Unexpected Config Error with discriminator

[gluhar2006]

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

Discriminator validation.

Expected: ValidationError when passing list or dict as discriminator.

Received: ConfigError.

Example Code

from typing import Literal

import pydantic


class Model1(pydantic.BaseModel):
    target: Literal["t1"]
    a: int


class Model2(pydantic.BaseModel):
    target: Literal["t2"]
    b: int


class Foo(pydantic.BaseModel):
    foo: Model1 | Model2 = pydantic.Field(discriminator="target")


# Foo(**{"foo": {"target": []}})
Foo(**{"foo": {"target": {}}})

Python, Pydantic & OS Version

pydantic version: 1.10.2
            pydantic compiled: True
                 install path: /home/.../lib/python3.10/site-packages/pydantic
               python version: 3.10.8 (main, Oct 19 2022, 10:31:59) [GCC 9.4.0]
                     platform: Linux-5.15.0-53-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
• Plugins and integration with other tools - mypy, FastAPI, python-devtools, Hypothesis, VS Code, PyCharm, etc.

[PrettyWood]

The real error is there TypeError: unhashable type: 'list' but TypeError is caught to raise a ConfigError indeed.

[gluhar2006]

I wrote about error, which received by user.
I just didn't understand https://github.com/pydantic/pydantic/blob/v1.10.2/pydantic/fields.py#L1124 otherwise I would have created PR, not issue

[fatelei]

I wrote about error, which received by user. I just didn't understand https://github.com/pydantic/pydantic/blob/v1.10.2/pydantic/fields.py#L1124 otherwise I would have created PR, not issue

discriminator decide target can be Model1 or Model2

example

Foo(foo={'target': 't1', 'a': 1})  # this is Model1

Foo(foo={'target': 't2', 'b': 1})  # this is Model2

Usage below is not right

Foo(**{"foo": {"target": {}}})

[fatelei]

this is not a bug

[gluhar2006]

this is not a bug

You mean that I need to validate target field separately or something else?

Usage below is not right

Why do you think so?

[fatelei]

Foo(foo={'target': 't2', 'b': 1})

target should not be {}, target should be one of t1 / t2

[gluhar2006]

target should not be {}, target should be one of t1 / t2

sounds weird

In this case how to explain that all works correctly with

Foo(**{"foo": {"target": 123}})?

[derek-globus]

The bug report seems to be about the error handling itself.

Foo(**{"foo": {"target": 123}})

raises a ValidationError indicating the document failed validation

Foo(**{"foo": {"target": []}})

raises a ConfigError indicating the Model is incorrect

---

Both documents should be invalid and thus should both raise ValidationErrors

[adriangb]

This will be fixed when we release v2:

from typing import Literal

import pydantic


class Model1(pydantic.BaseModel):
    target: Literal['t1']
    a: int


class Model2(pydantic.BaseModel):
    target: Literal['t2']
    b: int


class Foo(pydantic.BaseModel):
    foo: Model1 | Model2 = pydantic.Field(discriminator='target')


print(Foo(**{"foo": {"target": 't2', 'b': 123}}))
#> foo=Model2(target='t2', b=123)

Foo(**{"foo": {"target": []}})
"""
pydantic_core._pydantic_core.ValidationError: 1 validation error for Foo
foo
  Input should be a valid string [type=string_type, input_value=[], input_type=list]
"""
Foo(**{'foo': {'target': {}}})
"""
pydantic_core._pydantic_core.ValidationError: 1 validation error for Foo
foo
  Input should be a valid string [type=string_type, input_value={}, input_type=dict]
"""
Foo(**{"foo": {"target": 123}})
"""
pydantic_core._pydantic_core.ValidationError: 1 validation error for Foo
foo
    Input tag '123' found using 'target' does not match any of the expected tags: 't1', 't2' [type=union_tag_invalid, input_value={'target': 123}, input_type=dict]
"""