tiangolo.fastapi/fastapi/exceptions.py

from collections.abc import Mapping, Sequence
from typing import Annotated, Any, TypedDict

from annotated_doc import Doc
from pydantic import BaseModel, create_model
from starlette.exceptions import HTTPException as StarletteHTTPException
from starlette.exceptions import WebSocketException as StarletteWebSocketException


class EndpointContext(TypedDict, total=False):
    function: str
    path: str
    file: str
    line: int


class HTTPException(StarletteHTTPException):
    """
    An HTTP exception you can raise in your own code to show errors to the client.

    This is for client errors, invalid authentication, invalid data, etc. Not for server
    errors in your code.

    Read more about it in the
    [FastAPI docs for Handling Errors](https://fastapi.tiangolo.com/tutorial/handling-errors/).

    ## Example

    ```python
    from fastapi import FastAPI, HTTPException

    app = FastAPI()

    items = {"foo": "The Foo Wrestlers"}


    @app.get("/items/{item_id}")
    async def read_item(item_id: str):
        if item_id not in items:
            raise HTTPException(status_code=404, detail="Item not found")
        return {"item": items[item_id]}
    ```
    """

    def __init__(
        self,
        status_code: Annotated[
            int,
            Doc(
                """
                HTTP status code to send to the client.

                Read more about it in the
                [FastAPI docs for Handling Errors](https://fastapi.tiangolo.com/tutorial/handling-errors/#use-httpexception)
                """
            ),
        ],
        detail: Annotated[
            Any,
            Doc(
                """
                Any data to be sent to the client in the `detail` key of the JSON
                response.

                Read more about it in the
                [FastAPI docs for Handling Errors](https://fastapi.tiangolo.com/tutorial/handling-errors/#use-httpexception)
                """
            ),
        ] = None,
        headers: Annotated[
            Mapping[str, str] | None,
            Doc(
                """
                Any headers to send to the client in the response.

                Read more about it in the
                [FastAPI docs for Handling Errors](https://fastapi.tiangolo.com/tutorial/handling-errors/#add-custom-headers)

                """
            ),
        ] = None,
    ) -> None:
        super().__init__(status_code=status_code, detail=detail, headers=headers)


class WebSocketException(StarletteWebSocketException):
    """
    A WebSocket exception you can raise in your own code to show errors to the client.

    This is for client errors, invalid authentication, invalid data, etc. Not for server
    errors in your code.

    Read more about it in the
    [FastAPI docs for WebSockets](https://fastapi.tiangolo.com/advanced/websockets/).

    ## Example

    ```python
    from typing import Annotated

    from fastapi import (
        Cookie,
        FastAPI,
        WebSocket,
        WebSocketException,
        status,
    )

    app = FastAPI()

    @app.websocket("/items/{item_id}/ws")
    async def websocket_endpoint(
        *,
        websocket: WebSocket,
        session: Annotated[str | None, Cookie()] = None,
        item_id: str,
    ):
        if session is None:
            raise WebSocketException(code=status.WS_1008_POLICY_VIOLATION)
        await websocket.accept()
        while True:
            data = await websocket.receive_text()
            await websocket.send_text(f"Session cookie is: {session}")
            await websocket.send_text(f"Message text was: {data}, for item ID: {item_id}")
    ```
    """

    def __init__(
        self,
        code: Annotated[
            int,
            Doc(
                """
                A closing code from the
                [valid codes defined in the specification](https://datatracker.ietf.org/doc/html/rfc6455#section-7.4.1).
                """
            ),
        ],
        reason: Annotated[
            str | None,
            Doc(
                """
                The reason to close the WebSocket connection.

                It is UTF-8-encoded data. The interpretation of the reason is up to the
                application, it is not specified by the WebSocket specification.

                It could contain text that could be human-readable or interpretable
                by the client code, etc.
                """
            ),
        ] = None,
    ) -> None:
        super().__init__(code=code, reason=reason)


RequestErrorModel: type[BaseModel] = create_model("Request")
WebSocketErrorModel: type[BaseModel] = create_model("WebSocket")


class FastAPIError(RuntimeError):
    """
    A generic, FastAPI-specific error.
    """


class DependencyScopeError(FastAPIError):
    """
    A dependency declared that it depends on another dependency with an invalid
    (narrower) scope.
    """


class ValidationException(Exception):
    """Base exception for request data validation errors.

    Stores validation errors and optional endpoint context for enhanced
    error messages that include the source file, line, and path of the
    endpoint that triggered the validation failure.
    """

    def __init__(
        self,
        errors: Sequence[Any],
        *,
        endpoint_ctx: EndpointContext | None = None,
    ) -> None:
        self._errors = errors
        self.endpoint_ctx = endpoint_ctx

        ctx = endpoint_ctx or {}
        self.endpoint_function = ctx.get("function")
        self.endpoint_path = ctx.get("path")
        self.endpoint_file = ctx.get("file")
        self.endpoint_line = ctx.get("line")

    def errors(self) -> Sequence[Any]:
        return self._errors

    def _format_endpoint_context(self) -> str:
        if not (self.endpoint_file and self.endpoint_line and self.endpoint_function):
            if self.endpoint_path:
                return f"\n  Endpoint: {self.endpoint_path}"
            return ""

        context = f'\n  File "{self.endpoint_file}", line {self.endpoint_line}, in {self.endpoint_function}'
        if self.endpoint_path:
            context += f"\n    {self.endpoint_path}"
        return context

    def __str__(self) -> str:
        message = f"{len(self._errors)} validation error{'s' if len(self._errors) != 1 else ''}:\n"
        for err in self._errors:
            message += f"  {err}\n"
        message += self._format_endpoint_context()
        return message.rstrip()


class RequestValidationError(ValidationException):
    """Raised when incoming request data fails validation.

    Includes the request body that failed validation, accessible via the
    ``body`` attribute. Handled by default to return a 422 Unprocessable
    Entity response.
    """

    def __init__(
        self,
        errors: Sequence[Any],
        *,
        body: Any = None,
        endpoint_ctx: EndpointContext | None = None,
    ) -> None:
        super().__init__(errors, endpoint_ctx=endpoint_ctx)
        self.body = body


class WebSocketRequestValidationError(ValidationException):
    """Raised when incoming WebSocket request data fails validation.

    Similar to ``RequestValidationError`` but for WebSocket endpoints.
    Handled by default to close the WebSocket connection with a 1008
    Policy Violation code.
    """

    def __init__(
        self,
        errors: Sequence[Any],
        *,
        endpoint_ctx: EndpointContext | None = None,
    ) -> None:
        super().__init__(errors, endpoint_ctx=endpoint_ctx)


class ResponseValidationError(ValidationException):
    """Raised when outgoing response data fails validation.

    Includes the response body that failed validation, accessible via
    the ``body`` attribute. This is raised when a response model is set
    and the returned data does not match it.
    """

    def __init__(
        self,
        errors: Sequence[Any],
        *,
        body: Any = None,
        endpoint_ctx: EndpointContext | None = None,
    ) -> None:
        super().__init__(errors, endpoint_ctx=endpoint_ctx)
        self.body = body


class PydanticV1NotSupportedError(FastAPIError):
    """
    A pydantic.v1 model is used, which is no longer supported.
    """


class FastAPIDeprecationWarning(UserWarning):
    """
    A custom deprecation warning as DeprecationWarning is ignored
    Ref: https://sethmlarson.dev/deprecations-via-warnings-dont-work-for-python-libraries
    """