Method open

src/flask/testing.py:204–247

(
        self,
        *args: t.Any,
        buffered: bool = False,
        follow_redirects: bool = False,
        **kwargs: t.Any,
    )

            builder.close()

    def open(
        self,
        *args: t.Any,
        buffered: bool = False,
        follow_redirects: bool = False,
        **kwargs: t.Any,
    ) -> TestResponse:
        if args and isinstance(
            args[0], (werkzeug.test.EnvironBuilder, dict, BaseRequest)
        ):
            if isinstance(args[0], werkzeug.test.EnvironBuilder):
                builder = copy(args[0])
                builder.environ_base = self._copy_environ(builder.environ_base or {})  # type: ignore[arg-type]
                request = builder.get_request()
            elif isinstance(args[0], dict):
                request = EnvironBuilder.from_environ(
                    args[0], app=self.application, environ_base=self._copy_environ({})
                ).get_request()
            else:
                # isinstance(args[0], BaseRequest)
                request = copy(args[0])
                request.environ = self._copy_environ(request.environ)
        else:
            # request is None
            request = self._request_from_builder_args(args, kwargs)

        # Pop any previously preserved contexts. This prevents contexts
        # from being preserved across redirects or multiple requests
        # within a single block.
        self._context_stack.close()

        response = super().open(
            request,
            buffered=buffered,
            follow_redirects=follow_redirects,
        )
        response.json_module = self.application.json  # type: ignore[assignment]

        # Re-push contexts that were preserved during the request.
        for cm in self._new_contexts:
            self._context_stack.enter_context(cm)

        self._new_contexts.clear()
        return response

    def __enter__(self) -> FlaskClient:
        if self.preserve_context: