@Experimental
@Immutable
@Provider
public interface Node {

    /**
     * @return artifact for this node
     */
    @Nullable
    Artifact getArtifact();

    /**
     * @return dependency for this node
     */
    @Nullable
    Dependency getDependency();

    /**
     * Gets the child nodes of this node.
     *
     * @return the child nodes of this node, never {@code null}
     */
    @Nonnull

	if n < 0 {
		return 0, ErrNegativeCount
	}
	if n == 0 {
		return
	}

	b.lastByte = -1
	b.lastRuneSize = -1

	remain := n
	for {
		skip := b.Buffered()
		if skip == 0 {
			b.fill()
			skip = b.Buffered()
		}
		if skip > remain {
			skip = remain
		}
		b.r += skip
		remain -= skip
		if remain == 0 {
			return n, nil
		}
		if b.err != nil {

### 触发 `HTTPException`

`HTTPException` 是额外包含了和 API 有关数据的常规 Python 异常。

因为是 Python 异常，所以不能 `return`，只能 `raise`。

如在调用*路径操作函数*里的工具函数时，触发了 `HTTPException`，FastAPI 就不再继续执行*路径操作函数*中的后续代码，而是立即终止请求，并把 `HTTPException` 的 HTTP 错误发送至客户端。

在介绍依赖项与安全的章节中，您可以了解更多用 `raise` 异常代替 `return` 值的优势。

本例中，客户端用 `ID` 请求的 `item` 不存在时，触发状态码为 `404` 的异常：

{* ../../docs_src/handling_errors/tutorial001.py hl[11] *}

### 响应结果

)


@app.get("/items/")
async def read_items(token: Optional[str] = Security(oauth2_scheme)):
    return {"token": token}


client = TestClient(app)


def test_no_token():
    response = client.get("/items")
    assert response.status_code == 401, response.text
    assert response.json() == {"detail": "Not authenticated"}


def test_incorrect_token():

                "HTTPValidationError": {
                    "title": "HTTPValidationError",
                    "type": "object",
                    "properties": {
                        "detail": {
                            "title": "Detail",
                            "type": "array",
                            "items": {"$ref": "#/components/schemas/ValidationError"},
                        }
                    },

    p: Annotated[Optional[list[str]], Body(embed=True)] = None,
):
    return {"p": p}


class BodyModelOptionalListStr(BaseModel):
    p: Optional[list[str]] = None


@app.post("/model-optional-list-str", operation_id="model_optional_list_str")
async def read_model_optional_list_str(p: BodyModelOptionalListStr):
    return {"p": p.p}


@pytest.mark.parametrize(
    "path",

                "HTTPValidationError": {
                    "title": "HTTPValidationError",
                    "type": "object",
                    "properties": {
                        "detail": {
                            "title": "Detail",
                            "type": "array",
                            "items": {"$ref": "#/components/schemas/ValidationError"},
                        }
                    },

app = FastAPI()


def get_header(*, someheader: str = Header()):
    return someheader


def get_something_else(*, someheader: str = Depends(get_header)):
    return f"{someheader}123"


@app.get("/")
def get_deps(dep1: str = Depends(get_header), dep2: str = Depends(get_something_else)):
    return {"dep1": dep1, "dep2": dep2}


client = TestClient(app)

schema = {
    "components": {

        "components": {
            "schemas": {
                "HTTPValidationError": {
                    "properties": {
                        "detail": {
                            "items": {"$ref": "#/components/schemas/ValidationError"},
                            "title": "Detail",
                            "type": "array",
                        }
                    },
                    "title": "HTTPValidationError",

                },
                "HTTPValidationError": {
                    "properties": {
                        "detail": {
                            "items": {"$ref": "#/components/schemas/ValidationError"},
                            "type": "array",
                            "title": "Detail",
                        }
                    },
                    "type": "object",