将Flask路由参数传递给装饰器

Question

I have written a decorator that attempts to check we have post data for a Flask POST route:

Here's my decorator:

def require_post_data(required_fields=None):
    def decorator(f):
        @wraps(f)
        def decorated_function(*args, **kwargs):
            for required_field in required_fields:
                if not request.form.get(required_field, None):
                    return jsonify({"error": "Missing %s from post data." %
                                    required_field}), 400
            else:
                if not request.form:
                    return jsonify({"error": "No post data, aborting."}), 400
            return f(*args, **kwargs)
        return decorated_function
    return decorator

And I have two routes, with with a URL param and the other without:

from flask import Blueprint, jsonify, request

mod = Blueprint('contacts', __name__, url_prefix='/contacts')


@mod.route('/', methods=['POST'])
@require_post_data(['customer_id', 'some_other_required_field'])
def create_contact():
    # Do some business


@mod.route('/<int:contact_id>', methods=['POST'])
@require_post_data
def update_contact(contact_id):
    # Do some business

When I run a test that hits update_contact , I'm getting the following exception:

TypeError: decorator() got an unexpected keyword argument 'contact_id'

But it looks like create_contact is working as expected.

Why is contact_id being passed into decorator() ?

Answer 1

I believe you're just missing one thing, which is to actually call require_post_data to produce a decorator function in the update_contact route. This should fix it:

@mod.route('/<int:contact_id>', methods=['POST'])
@require_post_data() # <- note the parens
def update_contact(contact_id):
    # Do some business

The detailed explanation is that what you expected to happen (and what is happening in create contact ) is that the the view function is being modified by the decorator produced by require_post_data . In your update_contact above, what is actually happening is that the view function is being passed to require_post_data itself and simply used as the value of the required_fields parameter. This doesn't cause an error so require_post_data happily returns decorator which is then routed to when you hit /<int> , causing it to be passed contact_id as a keyword argument, resulting in the error you saw.