From_pydantic fails on union type

[tobiasBora]

Describe the Bug

If I do:

QuestionType = Annotated[Union[QuestionMultipleChoiceType, QuestionTextType, QuestionNumberType],
                         strawberry.union("Question")]

Then I'm not able to call:

QuestionType.from_pydantic(question)

as from_pydantic does not exist on union types.

MWE:

import strawberry
import operator
from pydantic import BaseModel, TypeAdapter
from typing import Union, Literal, Annotated
from strawberry.schema.config import StrawberryConfig

# Pedantic classes
class QuestionMultipleChoice(BaseModel):
    # This helps pydantic to distinguish the types
    kind: str = "QuestionMultipleChoice"
    nbChoices: int

class QuestionText(BaseModel):
    kind: str = "QuestionText"
    
class QuestionNumber(BaseModel):
    kind: str = "QuestionNumber"

Question = Union[
    QuestionMultipleChoice,
    QuestionText,
    QuestionNumber
]

# GraphQL types

@strawberry.experimental.pydantic.type(model=QuestionMultipleChoice, all_fields=True)
class QuestionMultipleChoiceType:
    pass

@strawberry.experimental.pydantic.type(model=QuestionText, all_fields=True)
class QuestionTextType:
    pass

@strawberry.experimental.pydantic.type(model=QuestionNumber, all_fields=True)
class QuestionNumberType:
    pass

# Redefining all types in the union seems very verbose and error-prone. Is this really the good approach?
QuestionType = Annotated[Union[QuestionMultipleChoiceType, QuestionTextType, QuestionNumberType],
                         strawberry.union("Question")]

# Fake a redis database

data = {
    "questionA": QuestionMultipleChoice(nbChoices=4).model_dump_json(),
    "questionB": QuestionText().model_dump_json(),
    "questionC": QuestionNumber().model_dump_json(),
}
print(data)

@strawberry.type
class Query:
    @strawberry.field
    def get_ident(self, questionID: str) -> QuestionType:
        question = TypeAdapter(Question).validate_json(data[questionID])
        print("question:", question)
        return QuestionType.from_pydantic(question)

config = StrawberryConfig(
    default_resolver=operator.getitem
)

schema = strawberry.Schema(query=Query, config=config)

System Information

• Operating system: NixOs
• Strawberry version (if applicable): 0.237.3

Additional Context