Support dictionaries in structured output

[chrisheecho]

client = genai.Client()

async def main():
    class Foo(BaseModel):
        foo: dict[str, int]

    await client.aio.models.generate_content(
        model="gemini-2.0-flash",
        contents="Please populate all fields of the following model with random values",
        config={
            "response_mime_type": "application/json",
            "response_schema": Foo,
        }
    )


if __name__ == "__main__":
    asyncio.run(main())

pydantic_core._pydantic_core.ValidationError: 1 validation error for Schema
properties.foo.additionalProperties
  Extra inputs are not permitted [type=extra_forbidden, input_value={'type': 'integer'}, input_type=dict]
    For further information visit https://errors.pydantic.dev/2.10/v/extra_forbidden

To achieve the above, I would need to refactor my model into something utterly disgusting:

client = genai.Client()

async def main():

    class Bar(BaseModel):
        key: str
        value: int

    class Foo(BaseModel):
        foo: list[Bar]

    return (await client.aio.models.generate_content(

        model="gemini-2.0-flash",
        contents="Please populate all fields of the following model with random values",
        config={
            "response_mime_type": "application/json",
            "response_schema": Foo,
        }
    )).parsed

if __name__ == "__main__":
    print(asyncio.run(main()))

Using a straight up dict also does not work:

client = genai.Client()

async def main():
    return (await client.aio.models.generate_content(
        model="gemini-2.0-flash",
        contents="Please populate all fields of the following model with random values",
        config={
            "response_mime_type": "application/json",
            "response_schema": dict[str, int],
        }
    )).parsed

if __name__ == "__main__":
    print(asyncio.run(main()))

additionalProperties
  Extra inputs are not permitted [type=extra_forbidden, input_value={'type': 'integer'}, input_type=dict]
    For further information visit https://errors.pydantic.dev/2.10/v/extra_forbidden

[sasha-gitg]

Closing in favor of: #70