Discriminator value represented in 'loc' of an error when ValidationError raised

[alice-luc]

Initial Checks

• I confirm that I'm using Pydantic V2

Description

When using List[Annotated[Union]] field with discriminator, its value appears in location tuple

Error i get
{
'input': '654f',
'loc': ('h', 'g', 0, 'c-discriminator', 'e', 'a'),
'msg': 'Input should be a valid integer, unable to parse string as an integer',
'type': 'int_parsing',
'url': 'https://errors.pydantic.dev/2.3/v/int_parsing'
}

Expected error
{
'input': '654f',
'loc': ('h', 'g', 0, 'e', 'a'),
'msg': 'Input should be a valid integer, unable to parse string as an integer',
'type': 'int_parsing',
'url': 'https://errors.pydantic.dev/2.3/v/int_parsing'
}

Example Code

from pprint import pprint
from typing import Annotated, Union, Literal, Any

from pydantic import BaseModel as BM, ConfigDict, Field, field_validator


class BaseModel(BM):
    model_config = ConfigDict(extra='forbid')


class A(BaseModel):
    a: int = 1
    b: str = "12345"


class B(BaseModel):
    c: int = 2
    d: str = "qwe"


class C(BaseModel):
    e: A
    t: Literal["c-discriminator"]


class D(BaseModel):
    f: C
    t: Literal["d-discriminator"]


DC = Annotated[
    Union[D, C],
    Field(discriminator="t")]


class F(BaseModel):
    g: list[DC]

    @field_validator("g", mode='before')
    def pre_root(cls, values: list[dict[str, Any]]):

        for v in values["g"]:
            if "e" in v:
                v["t"] = "c-discriminator"
            elif "f" in v:
                v["t"] = "d-discriminator"
        return values


class G(BaseModel):
    h: F


try:
    f = G(**{"h": {"g": [{"e": {"a": "654f"}}]}})
except Exception as e:
    pprint(e.errors())

Python, Pydantic & OS Version

pydantic version: 2.3.0
pydantic-core version: 2.6.3
pydantic-core build: profile=release pgo=false
install path: /[location]/lib/python3.11/site-packages/pydantic
python version: 3.11.4 (v3.11.4:d2340ef257, Jun  6 2023, 19:15:51) [Clang 13.0.0 (clang-1300.0.29.30)]
platform: macOS-13.5.2-arm64-arm-64bit
optional deps. installed: ['typing-extensions']

[sydney-runkle]

Hi @alice-luc,

Thanks for your question!

This is related to #7261 - specifically, see this comment. Let me know if you have any other questions!