stripe: Link InvoiceItem to Invoice.

This is required for upgrading to the basil version of stripe.
Changes haven't been tested in this commit. It is just for easy
verification of changes.

corporate/lib/stripe.py

@@ -3216,25 +3216,32 @@ class BillingSession(ABC):
                 licenses_base = plan.invoiced_through.licenses
                 invoiced_through_id = plan.invoiced_through.id
 
+            # Invoice Variables
+            stripe_invoice: stripe.Invoice | None = None
+            need_to_invoice = False
+
             # Track if we added renewal invoice item which is possibly eligible for discount.
             renewal_invoice_period: stripe.InvoiceItem.CreateParamsPeriod | None = None
             for ledger_entry in LicenseLedger.objects.filter(
                 plan=plan, id__gt=invoiced_through_id, event_time__lte=event_time
             ).order_by("id"):
-                price_args: PriceArgs = {}
+                # InvoiceItem variables.
+                invoice_item_params = stripe.InvoiceItem.CreateParams(
+                    customer=plan.customer.stripe_customer_id
+                )
+
                 if ledger_entry.is_renewal:
                     if plan.fixed_price is not None:
                         amount_due = get_amount_due_fixed_price_plan(
                             plan.fixed_price, plan.billing_schedule
                         )
-                        price_args = {"amount": amount_due}
+                        invoice_item_params["amount"] = amount_due
                     else:
                         assert plan.price_per_license is not None  # needed for mypy
-                        price_args = {
+                        invoice_item_params["unit_amount"] = plan.price_per_license
-                            "unit_amount": plan.price_per_license,
+                        invoice_item_params["quantity"] = ledger_entry.licenses
-                            "quantity": ledger_entry.licenses,
+                    invoice_item_params["description"] = f"{plan.name} - renewal"
-                        }
+                    need_to_invoice = True
-                    description = f"{plan.name} - renewal"
                 elif (
                     plan.fixed_price is None
                     and licenses_base is not None
@@ -3260,61 +3267,15 @@ class BillingSession(ABC):
                             plan_renewal_or_end_date - ledger_entry.event_time
                         ) / (billing_period_end - last_renewal)
                         unit_amount = int(plan.price_per_license * proration_fraction + 0.5)
-                    price_args = {
+                    invoice_item_params["unit_amount"] = unit_amount
-                        "unit_amount": unit_amount,
+                    invoice_item_params["quantity"] = ledger_entry.licenses - licenses_base
-                        "quantity": ledger_entry.licenses - licenses_base,
+                    invoice_item_params["description"] = "Additional license ({} - {})".format(
-                    }
-                    description = "Additional license ({} - {})".format(
                         ledger_entry.event_time.strftime("%b %-d, %Y"),
                         plan_renewal_or_end_date.strftime("%b %-d, %Y"),
                     )
+                    need_to_invoice = True
 
-                if price_args:
+                if stripe_invoice is None and need_to_invoice:
-                    plan.invoiced_through = ledger_entry
-                    plan.invoicing_status = CustomerPlan.INVOICING_STATUS_STARTED
-                    plan.save(update_fields=["invoicing_status", "invoiced_through"])
-                    invoice_period = stripe.InvoiceItem.CreateParamsPeriod(
-                        start=datetime_to_timestamp(ledger_entry.event_time),
-                        end=datetime_to_timestamp(
-                            get_plan_renewal_or_end_date(plan, ledger_entry.event_time)
-                        ),
-                    )
-
-                    if ledger_entry.is_renewal:
-                        renewal_invoice_period = invoice_period
-
-                    stripe.InvoiceItem.create(
-                        currency="usd",
-                        customer=plan.customer.stripe_customer_id,
-                        description=description,
-                        discountable=False,
-                        period=invoice_period,
-                        idempotency_key=get_idempotency_key(ledger_entry),
-                        **price_args,
-                    )
-                # Update license base per ledger_entry.
-                licenses_base = ledger_entry.licenses
-                plan.invoiced_through = ledger_entry
-
-            if renewal_invoice_period is not None:
-                flat_discount, flat_discounted_months = self.get_flat_discount_info(plan.customer)
-                if plan.fixed_price is None and flat_discounted_months > 0:
-                    num_months = (
-                        12 if plan.billing_schedule == CustomerPlan.BILLING_SCHEDULE_ANNUAL else 1
-                    )
-                    flat_discounted_months = min(flat_discounted_months, num_months)
-                    discount = flat_discount * flat_discounted_months
-                    plan.customer.flat_discounted_months -= flat_discounted_months
-                    plan.customer.save(update_fields=["flat_discounted_months"])
-                    stripe.InvoiceItem.create(
-                        currency="usd",
-                        customer=plan.customer.stripe_customer_id,
-                        description=f"${cents_to_dollar_string(flat_discount)}/month new customer discount",
-                        # Negative value to apply discount.
-                        amount=(-1 * discount),
-                        period=renewal_invoice_period,
-                    )
-
                     if plan.charge_automatically:
                         collection_method: Literal["charge_automatically", "send_invoice"] = (
                             "charge_automatically"
@@ -3332,6 +3293,57 @@ class BillingSession(ABC):
                     if days_until_due is not None:
                         invoice_params["days_until_due"] = days_until_due
                     stripe_invoice = stripe.Invoice.create(**invoice_params)
+
+                if invoice_item_params.get("description") is not None:
+                    invoice_period = stripe.InvoiceItem.CreateParamsPeriod(
+                        start=datetime_to_timestamp(ledger_entry.event_time),
+                        end=datetime_to_timestamp(
+                            get_plan_renewal_or_end_date(plan, ledger_entry.event_time)
+                        ),
+                    )
+
+                    if ledger_entry.is_renewal:
+                        renewal_invoice_period = invoice_period
+
+                    invoice_item_params["currency"] = "usd"
+                    invoice_item_params["discountable"] = False
+                    invoice_item_params["period"] = invoice_period
+                    invoice_item_params["idempotency_key"] = get_idempotency_key(ledger_entry)
+                    assert stripe_invoice is not None
+                    assert stripe_invoice.id is not None
+                    invoice_item_params["invoice"] = stripe_invoice.id
+                    stripe.InvoiceItem.create(**invoice_item_params)
+
+                # Update license base per ledger_entry.
+                licenses_base = ledger_entry.licenses
+                plan.invoiced_through = ledger_entry
+
+            flat_discount, flat_discounted_months = self.get_flat_discount_info(plan.customer)
+            if stripe_invoice is not None:
+                # Only apply discount if this invoice contains renewal of the plan.
+                if (
+                    renewal_invoice_period is not None
+                    and plan.fixed_price is None
+                    and flat_discounted_months > 0
+                ):
+                    assert stripe_invoice.id is not None
+                    num_months = (
+                        12 if plan.billing_schedule == CustomerPlan.BILLING_SCHEDULE_ANNUAL else 1
+                    )
+                    flat_discounted_months = min(flat_discounted_months, num_months)
+                    discount = flat_discount * flat_discounted_months
+                    plan.customer.flat_discounted_months -= flat_discounted_months
+                    plan.customer.save(update_fields=["flat_discounted_months"])
+                    stripe.InvoiceItem.create(
+                        invoice=stripe_invoice.id,
+                        currency="usd",
+                        customer=plan.customer.stripe_customer_id,
+                        description=f"${cents_to_dollar_string(flat_discount)}/month new customer discount",
+                        # Negative value to apply discount.
+                        amount=(-1 * discount),
+                        period=renewal_invoice_period,
+                    )
+
                 stripe.Invoice.finalize_invoice(stripe_invoice)
 
         plan.invoicing_status = CustomerPlan.INVOICING_STATUS_DONE