Using resources from dependencies with `yield` in background tasks is no longer supported.

This change is what supports the new features, read below. 🤓

### Dependencies with `yield`, `HTTPException` and Background Tasks

Dependencies with `yield` now can raise `HTTPException` and other exceptions after `yield`. 🎉

                It can contain several fields.

                * `name`: (`str`) **REQUIRED** (if a `license_info` is set). The
                    license name used for the API.
                * `identifier`: (`str`) An [SPDX](https://spdx.dev/) license expression
                    for the API. The `identifier` field is mutually exclusive of the `url`
                    field. Available since OpenAPI 3.1.0, FastAPI 0.99.0.

                response_field = create_response_field(name=response_name, type_=model)
                response_fields[additional_status_code] = response_field
        if response_fields:
            self.response_fields: Dict[Union[int, str], ModelField] = response_fields
        else:
            self.response_fields = {}

        assert callable(endpoint), "An endpoint must be a callable"

    ```

For example, in one of the ways the OAuth2 specification can be used (called "password flow") it is required to send a `username` and `password` as form fields.

The <abbr title="specification">spec</abbr> requires the fields to be exactly named `username` and `password`, and to be sent as form fields, not JSON.

```

!!! tip
    Pydantic 是 FastAPI 中所有数据验证和序列化的核心，当你在没有设默认值的情况下使用 `Optional` 或 `Union[Something, None]` 时，它具有特殊行为，你可以在 Pydantic 文档中阅读有关<a href="https://docs.pydantic.dev/latest/concepts/models/#required-optional-fields" class="external-link" target="_blank">必需可选字段</a>的更多信息。

### 使用Pydantic中的`Required`代替省略号(`...`)

如果你觉得使用 `...` 不舒服，你也可以从 Pydantic 导入并使用 `Required`：

```Python hl_lines="2  8"

!!! tip "Tipp"

            Pydantic's `include` parameter, passed to Pydantic models to set the
            fields to include.
            """
        ),
    ] = None,
    exclude: Annotated[
        Optional[IncEx],
        Doc(
            """
            Pydantic's `exclude` parameter, passed to Pydantic models to set the
            fields to exclude.
            """
        ),
    ] = None,
    by_alias: Annotated[

    Por exemplo, você pode usar isso para adicionar metadados para uma interface de usuário de front-end, etc.

## `Field` de argumentos adicionais

Ao usar `Field ()` com modelos Pydantic, você também pode declarar informações extras para o **JSON Schema** passando quaisquer outros argumentos arbitrários para a função.

# Body - Nested Models

With **FastAPI**, you can define, validate, document, and use arbitrarily deeply nested models (thanks to Pydantic).

## List fields

You can define an attribute to be a subtype. For example, a Python `list`:

=== "Python 3.10+"

    ```Python hl_lines="12"
    {!> ../../../docs_src/body_nested_models/tutorial001_py310.py!}
    ```

=== "Python 3.8+"

    ```Python hl_lines="14"

    ```

=== "Python 3.8+"

    ```Python hl_lines="15-23"
    {!> ../../../docs_src/schema_extra_example/tutorial001.py!}
    ```

这些额外的信息将按原样添加到输出的JSON模式中。

## `Field` 的附加参数

在 `Field`, `Path`, `Query`, `Body` 和其他你之后将会看到的工厂函数，你可以为JSON 模式声明额外信息，你也可以通过给工厂函数传递其他的任意参数来给JSON 模式声明额外信息，比如增加 `example`:

=== "Python 3.10+"

    ```Python hl_lines="2  8-11"