AssertionError：如果未提供端点，则预期视图函数 - python

Question

trying to decorate end point with requires_fields decorator. this is the implementation.

import functools
from flask import request, jsonify

def requires_fields(fields):
    required_fields = set(fields)

    def wrapper(func):
        @functools.wraps(func)
        def decorated(*args, **kwargs):
            current_fields = set(request.get_json().keys())
            missing_fields = required_fields - current_fields
            if missing_fields:
                return jsonify({'error': 'missing fields', 'fields': list(missing_fields)}), 400  # Bad Request
            resp = func(*args, **kwargs)
            return resp
    return wrapper

@app.route('/is_registered', methods=['POST'])
@requires_fields(['mobile'])
def is_registered():
    _json = request.get_json()
    keys = _json.keys()
    customer = Customer()
    registered = False

    response = verify_required_params(['mobile'], keys)
    if response:
        return response

    _mobile = _json['mobile']

    validated = validate_mobile(_mobile)
    cust, response_code = customer.get(_mobile)
    if cust is not None and cust['id']:
        registered = True

    if not validated:
        response = responses.get(MOBILE_NUMBER_NOT_VALID)
        return jsonify(response)

    if not registered:
        response = responses.get(MOBILE_NUMBER_NOT_REGISTERED)
        return jsonify(response)

    response = responses.get(MOBILE_NUMBER_REGISTERED)
    return jsonify(response)

It is giving me this error:

assert view_func is not None, "expected view func if endpoint is not provided."
AssertionError: expected view func if endpoint is not provided.

What is causing this issue? How can we fix this?

Answer 1

You forgot to return the decorated function from the wrapper function.

When you do @wrapper on top of a function test for instance, you are basically writing test = wrapper(test) .

Since wrapper does not return anything, you get an error.

So basically you need to do:

def requires_fields(fields):
    required_fields = set(fields)
    def wrapper(func):
        @functools.wraps(func)
        def decorated(*args, **kwargs):
            # ...
        return decorated # you are missing this
    return wrapper