Cannot specify billing_cycle_anchor attribute for a Subscription

[PabloCastellano]

According to the documentation the billing_cycle_anchor attribute can be used when creating and updating a subscription.

billing_cycle_anchor (timestamp)

Determines the date of the first full invoice, and, for plans with month or year intervals, the day of the month for subsequent invoices.

This is particularly useful for the use case of Combining trials with billing cycle anchor.

As I understand, djstripe supports this option:

https://github.com/dj-stripe/dj-stripe/blob/master/djstripe/models/billing.py#L939

However when using customer.subscribe() you cannot specify this parameter

https://github.com/dj-stripe/dj-stripe/blob/master/djstripe/models/core.py#L512

I am willing to contribute but need some guidance. Is adding it as a parameter to that function and then when calling Subscription._api_create enough?

[PabloCastellano]

I've got it working in my branch.

import datetime
from dateutil.relativedelta import relativedelta

next_month = datetime.date.today() + relativedelta(months=1, day=1)                                                                                                                                                                 
ts = int(next_first.strftime("%s"))

subscription = customer.subscribe(plan, billing_cycle_anchor=ts)                                                                                                                                                

I've submitted two PRs, for master and stable-1.2

[therefromhere]

Thanks, that looks reasonable, I'll take a closer look later.

[blackboxoperations]

Be sure to note two things when leaning on the anchor like this:

1. It isn't odd anymore for everyone to have their own distinct subscription start date/time, as opposed to forcing everyone into a first/middle/last of the month start/stop date and pro-rate yourself into an early code grace unnecessarily

2. The billing_cycle_anchor is primarily about helping those who need to round off a cycle and pro-rate based on the remaining time, where the references above were emphasizing how you could add in a 7 day trial period and be sure that if there's any time left in the month, that it's pro-rated and invoiced specifically and accordingly.

Only reason I point this out is because the billing_cycle_anchor isn't meant to be a subscription trial period fix, so if and when a side-effect creeps up and bites anyone in the ass when using it, look in that direction first.