Method __init__

fastapi/routing.py:1855–1875

(
        self,
        *,
        directory: str | os.PathLike[str],
        fallback: Literal["auto", "index.html", "404.html"] | None,
        check_dir: bool = True,
    )

class _FrontendStaticFiles(StaticFiles):
    def __init__(
        self,
        *,
        directory: str | os.PathLike[str],
        fallback: Literal["auto", "index.html", "404.html"] | None,
        check_dir: bool = True,
    ) -> None:
        self.fallback = fallback
        if check_dir and not os.path.isdir(directory):
            raise RuntimeError(
                f"Frontend directory '{directory}' does not exist. "
                f"Resolved absolute path: '{_get_resolved_absolute_path(directory)}'"
            )
        super().__init__(
            directory=directory,
            html=True,
            check_dir=check_dir,
            follow_symlink=False,
        )
        if check_dir and fallback in {"index.html", "404.html"}:
            self._check_fallback_file(fallback)

    def _check_fallback_file(self, fallback: str) -> None:
        _, stat_result = self.lookup_path(fallback)