tmpl-fastapi/app/paths/errors.py

"""Custom error pages for FastAPI app"""

from pathlib import Path
from typing import List

from fastapi import Request, Response
from fastapi import HTTPException

from . import Paths
from .. import respond
from .. import common

# Add other HTTP error codes
codes: List[int] = [404, 500]


class ErrorsPaths(Paths):
    """Sets up custom error pages,
    inherited from paths.Paths"""

    def add_paths(self) -> None:

        # For each HTTP code specified above
        for code in codes:
            self.add_handler(code)
    
    def add_handler(self, code: int) -> None:
        """Adds an error handler to FastAPI app.
        Only for internal use!

        Args:
            code (int): HTTP error code
        """

        # Jinja template file name
        # e.g. 404.html for 404 code
        file = Path(common.templates_dir) / f'{code}.html'

        # Exit from the function
        # if the template does not exist
        if not file.exists():
            return

        @self.app.exception_handler(code)
        async def handler(req: Request, exc: HTTPException) -> Response:

            # Respond with the template
            return respond.with_tmpl(
                f'{code}.html',
                code=code,
                request=req,
                exc=exc,
            )