Variable "pydantic_core.core_schema.FieldValidationInfo" is not valid as a type

[sisp]

The deprecation of pydantic_core.core_schema.FieldValidationInfo in v2.10.0 makes mypy unhappy:

from pydantic_core.core_schema import FieldValidationInfo

def f(x: FieldValidationInfo):
    ...

$ mypy test.py
test.py:3: error: Variable "pydantic_core.core_schema.FieldValidationInfo" is not valid as a type  [valid-type]
test.py:3: note: See https://mypy.readthedocs.io/en/stable/common_issues.html#variables-vs-type-aliases
Found 1 error in 1 file (checked 1 source file)

No error occurs when using v2.9.0.

This behavior turns the deprecation into a breaking change (at least regarding type-checking). As a result, we can't update from Pydantic v2.3 to v2.4 as pydantic-core is a pinned dependency and bumped to v2.10.

[dmontagu]

@sisp The import name was just changed (with a fallback to keep older code working). From pydantic_core.core_schema:

_deprecated_import_lookup = {
    'FieldValidationInfo': ValidationInfo,
    'FieldValidatorFunction': WithInfoValidatorFunction,
    'GeneralValidatorFunction': WithInfoValidatorFunction,
    'FieldWrapValidatorFunction': WithInfoWrapValidatorFunction,
}

I think if you change the import to ValidationInfo instead of FieldValidationInfo the mypy error will go away.

[adriangb]

Also see pydantic/pydantic#7667

[sisp]

True, I still think a deprecation should not break untouched code, not even for type-checking. Is there a way to fix the original import to keep mypy happy?

[dmontagu]

I'm not taking a side in the "mypy errors are breaking changes" argument, but for what it's worth, you could add an if TYPE_CHECKING: block for mypy to see the import while still ensuring that it is importable with the deprecation warning (thanks to the getattr).

[adriangb]

I agree that might be the fix. If it works a PR to implement it would be welcome.

[sisp]

I've submitted a PR with the suggested fix: #995