env:
          GITHUB_CONTEXT: ${{ toJson(github) }}
        run: echo "$GITHUB_CONTEXT"
      - uses: actions/checkout@v4
        with:
          # To allow latest-changes to commit to the main branch
          token: ${{ secrets.FASTAPI_LATEST_CHANGES }}
      # Allow debugging with tmate
      - name: Setup tmate session
        uses: mxschmitt/action-tmate@v3

## Read the Tutorial first

The next sections assume you already read the main [Tutorial - User Guide: Security](../../tutorial/security/index.md){.internal-link target=_blank}.

    new_field.required = field.required  # type: ignore[misc]
    new_field.model_config = field.model_config  # type: ignore[attr-defined]
    new_field.field_info = field.field_info
    new_field.allow_none = field.allow_none  # type: ignore[attr-defined]
    new_field.validate_always = field.validate_always  # type: ignore[attr-defined]
    if field.sub_fields:  # type: ignore[attr-defined]

    */
  content: "\00A0[↪]";
}

a.internal-link::after {
  /* \00A0 is a non-breaking space
        to make the mark be on the same line as the link
    */
  content: "\00A0↪";
}

.shadow {
  box-shadow: 5px 5px 10px #999;
}

/* Give space to lower icons so Gitter chat doesn't get on top of them */
.md-footer-meta {
  padding-bottom: 2em;
}

.user-list {
  display: flex;
  flex-wrap: wrap;

app = FastAPI()


class InternalError(Exception):
    pass


def get_username():
    try:
        yield "Rick"
    except InternalError:
        print("We don't swallow the internal error here, we raise again 😎")
        raise


@app.get("/items/{item_id}")
def get_item(item_id: str, username: str = Depends(get_username)):
    if item_id == "portal-gun":
        raise InternalError(

from typing_extensions import Annotated

app = FastAPI()


class InternalError(Exception):
    pass


def get_username():
    try:
        yield "Rick"
    except InternalError:
        print("We don't swallow the internal error here, we raise again 😎")
        raise


@app.get("/items/{item_id}")
def get_item(item_id: str, username: Annotated[str, Depends(get_username)]):
    if item_id == "portal-gun":

app = FastAPI()


class InternalError(Exception):
    pass


def get_username():
    try:
        yield "Rick"
    except InternalError:
        print("We don't swallow the internal error here, we raise again 😎")
        raise


@app.get("/items/{item_id}")
def get_item(item_id: str, username: Annotated[str, Depends(get_username)]):
    if item_id == "portal-gun":

    width: 15px;
    height: 15px;
    border-radius: 50%;
    /* A little hack to display the window buttons in one pseudo element. */
    background: #d9515d;
    -webkit-box-shadow: 25px 0 0 #f4c025, 50px 0 0 #3ec930;
            box-shadow: 25px 0 0 #f4c025, 50px 0 0 #3ec930;
}

[data-termynal]:after {
    content: 'bash';
    position: absolute;
    color: var(--color-text-subtle);
    top: 5px;
    left: 0;

* Validate **complex structures**:
    * Use of hierarchical Pydantic models, Python `typing`’s `List` and `Dict`, etc.
    * And validators allow complex data schemas to be clearly and easily defined, checked and documented as JSON Schema.
    * You can have deeply **nested JSON** objects and have them all validated and annotated.
* **Extensible**:

!!! note
    FastAPI will know that the value of `q` is not required because of the default value `= None`.

    The `Union` in `Union[str, None]` is not used by FastAPI, but will allow your editor to give you better support and detect errors.

## Without Pydantic