JSON Schema & Pydantic's default factory.

[zcherry17]

Unless this is already a feature, I cannot find anything in the code base that supports this.
I am trying to make a schema that generates the following:

class Foo(BaseModel):
    my_list: list[int] = Field(default_factory=list)

Firstly, is there a reason why default factory is not supported? If there is not any particular reason, then a default factory should be generated for arrays in some meaningful way. Perhaps if the following schema was defined, then you would get the appropriate generation.

{
    "$id": "/foo",
    "$schema": "https://json-schema.org/draft/2020-12/schema",
    "title": "Foo",
    "type": "object",
    "properties": {
        "my_list": {
            "type": "array",
            "items": {"type": "integer"}
            "default": { "default_factory": "list" }
            < -- or -- >
            "default_factory": "list" < -- as I have seen that extra keys are supported in the code generator -->
        }
    }
}

[tommyjcarpenter]

I hit this exact same issue, and before finding this thread, wrote a workaround... here is my literal docstring:

parse_permissions(perms_dict: AnyManifest) -> PermissionsV2Bound:
    """
    I tried, endlessly, to get pydantic to spit out default_factory rather than None, when fields on the API are
    *optional* but *have defaults*
    The root of the problem is that we want optional fields to be allowed on the API, ie the user can omit them,
    but no Nones in the generated pydantic model.

    Basically see their example here: https://koxudaxi.github.io/datamodel-code-generator/
    What their example code produces is:

    apiUrl: Optional[AnyUrl] = Field(
        None, description="The URL describing the dataset's fields"
    )

    What I want is:

    apiUrl: Optional[AnyUrl] = Field(
        default_factory=AnyUrl, description="The URL describing the dataset's fields"
    )
    https://docs.pydantic.dev/usage/models/#field-with-dynamic-default-value

    Or in our case, instead of

        class PermissionsV2(BaseModel):
            class Config:
                extra = Extra.forbid

            version: Optional[VersionString] = "v2.1"
            apis: Optional[Apis] = None
            admin_ui: Optional[AdminUIPermissions] = None

    What I want:

    class PermissionsV2(BaseModel):
        ...
        apis: Optional[Apis] = field(default_factory=Apis)
        ...

    I tried every field here: https://github.com/koxudaxi/datamodel-code-generator#usage

    and I can't get it to do this! so for now this exists
    """

[koxudaxi]

@zcherry17 @tommyjcarpenter
I'm sorry for my too-late reply.
Now, the default factory is not supported.
I will implement the feature.
Thank you

[koxudaxi]

I just created the issue.
#1026

[koxudaxi]

@zcherry17 @tommyjcarpenter
I have released a new version 0.17.0.
The version supports default_factory attribute.
Thank you very much!!