"""
            Minimum length for strings.
            """
        ),
    ] = None,
    max_length: Annotated[
        Optional[int],
        Doc(
            """
            Maximum length for strings.
            """
        ),
    ] = None,
    pattern: Annotated[
        Optional[str],
        Doc(
            """
            RegEx pattern for strings.
            """
        ),

For example, you could make sure that each *path operation* has a tag, and then generate the operation ID based on the **tag** and the *path operation* **name** (the function name).

### Custom Generate Unique ID Function

FastAPI uses a **unique ID** for each *path operation*, it is used for the **operation ID** and also for the names of any needed custom models, for requests or responses.

class="external-link" target="_blank">existing pull requests</a> for your language. You can filter the pull requests by the ones with the label for your language. For example, for Spanish, the label is <a href="https://github.com/tiangolo/fastapi/pulls?q=is%3Aopen+sort%3Aupdated-desc+label%3Alang-es+label%3Aawaiting-review" class="external-link" target="_blank">`lang-es`</a>.

* Review those pull requests, requesting changes or approving them. For the languages I don't speak, I'll wait for several others...

## Pin your `fastapi` version

The first thing you should do is to "pin" the version of **FastAPI** you are using to the specific latest version that you know works correctly for your application.

For example, let's say you are using version `0.45.0` in your app.

    # Override main [project] configs with custom configs for this package
    for key, value in project_config.items():
        metadata[key] = value
    # Get custom build config for the current package
    build_config: Dict[str, Any] = (
        config.get("tool", {}).get("pdm", {}).get("build", {})
    )
    # Override PDM build config with custom build config for this package
    for key, value in build_config.items():

    for an OAuth2 password flow.

    The OAuth2 specification dictates that for a password flow the data should be
    collected using form data (instead of JSON) and that it should have the specific
    fields `username` and `password`.

    All the initialization parameters are extracted from the request.

    Read more about it in the

## Integrated middlewares

**FastAPI** includes several middlewares for common use cases, we'll see next how to use them.

!!! note "Technical Details"
    For the next examples, you could also use `from starlette.middleware.something import SomethingMiddleware`.

    **FastAPI** provides several middlewares in `fastapi.middleware` just as a convenience for you, the developer. But most of the available middlewares come directly from Starlette.

You could want to set up a different database for testing, rollback the data after the tests, pre-fill it with some testing data, etc.

The main idea is exactly the same you saw in that previous chapter.

## Add tests for the SQL app

And there was a web user interface for Swagger APIs already created. So, being able to generate Swagger documentation for an API would allow using this web user interface automatically.

At some point, Swagger was given to the Linux Foundation, to be renamed OpenAPI.

That's why when talking about version 2.0 it's common to say "Swagger", and for version 3+ "OpenAPI".

!!! check "Inspired **FastAPI** to"

@needs_pydanticv2
def test_model_field_default_required():
    # For coverage
    field_info = FieldInfo(annotation=str)
    field = ModelField(name="foo", field_info=field_info)
    assert field.default is Undefined


@needs_pydanticv1
def test_upload_file_dummy_with_info_plain_validator_function():
    # For coverage
    assert UploadFile.__get_pydantic_core_schema__(str, lambda x: None) == {}