Add catch_all_405s or ability to define custom error handler for 405 MethodNotAllowed Error

Errors 404 and 405 are treated in a special way by Flask-Restful (see _should_use_fr_error_handler()).

In case of 404 NotFound, we can set the catch_all_404s=False flag, so that Flask’s error handle will deal with the 404 NotFound exception.

There is no equivalent feature for 405 MethodNotAllowed. And so every time a request hits 405, the response will be {'message': 'The method is not allowed for the requested URL.'}. And that is even after registering custom error handler to Flask object: app.register_error_handler(Exception, my_custom_error_handler)

It would be really useful to be able to set catch_all_405s=False, or ideally be able to define our own error handler for 405 error.

Currently the only way to specify custom 405 error is by defining a non-dynamic dictionary: e.g.

    'MethodNotAllowed': {
        'type': 'MethodNotAllowed',
        'description': 'The method is not allowed for the requested URL.',
        'url': None,
        'data': None,
        'status': 405
    }

This however won’t allow us to update the dict elements such as ‘url’ in the given example.

[jakubczaplicki]

2 years later and I’ve hit this problem again. For those who may need this, here’s the solution.

If you want to replace the flask-restful 405 error message from

{"message": "The method is not allowed for the requested URL."}

to your custom message generated by your own handler , e.g.

{
 "description":"The method is not allowed for the requested URL.",
 "method":"GET",
 "type":"MethodNotAllowed",
 "url":"http://127.0.0.1:5000/v1/login"
}

you need to use Flask’s got_request_exception to catch when an exception happens during request processing:

application.py:

from flask import Flask, got_request_exception
from app.errors import custom_api_error_handler

def create_app(config_name='default'):
  app = Flask(__name__)
  got_request_exception.connect(custom_api_error_handler, app)
 # the rest of your code

errors.py:

from werkzeug.exceptions import HTTPException

def custom_api_error_handler(exception):
  payload = {
    'type': 'InternalServerError',
    'description': 'Internal Error',
    'method': request.method,
    'url': request.url
    }
  if isinstance(exception, HTTPException):
    payload['type'] = 'HTTPException'
    payload['description'] = exception.description
    status_code = exception.code
  else:
    payload['description'] = exception.args
    status_code = 500
  return jsonify(payload), status_code

[muteebakram]

Thank you for this 😃