FormDataRoutingRedirect Class — flask Architecture

Source Code

src/flask/debughelpers.py lines 50–78

class FormDataRoutingRedirect(AssertionError):
    """This exception is raised in debug mode if a routing redirect
    would cause the browser to drop the method or body. This happens
    when method is not GET, HEAD or OPTIONS and the status code is not
    307 or 308.
    """

    def __init__(self, request: Request) -> None:
        exc = request.routing_exception
        assert isinstance(exc, RequestRedirect)
        buf = [
            f"A request was sent to '{request.url}', but routing issued"
            f" a redirect to the canonical URL '{exc.new_url}'."
        ]

        if f"{request.base_url}/" == exc.new_url.partition("?")[0]:
            buf.append(
                " The URL was defined with a trailing slash. Flask"
                " will redirect to the URL with a trailing slash if it"
                " was accessed without one."
            )

        buf.append(
            " Send requests to the canonical URL, or use 307 or 308 for"
            " routing redirects. Otherwise, browsers will drop form"
            " data.\n\n"
            "This exception is only raised in debug mode."
        )
        super().__init__("".join(buf))