billing: Add backend for paying by invoice.

corporate/lib/stripe.py

@@ -34,6 +34,9 @@ log_to_file(logging.getLogger('stripe'), BILLING_LOG_PATH)
 
 CallableT = TypeVar('CallableT', bound=Callable[..., Any])
 
+MIN_INVOICED_SEAT_COUNT = 30
+DEFAULT_INVOICE_DAYS_UNTIL_DUE = 30
+
 def get_seat_count(realm: Realm) -> int:
     return UserProfile.objects.filter(realm=realm, is_active=True, is_bot=False).count()
 
@@ -202,7 +205,7 @@ def do_replace_coupon(user: UserProfile, coupon: Coupon) -> stripe.Customer:
 
 @catch_stripe_errors
 def do_subscribe_customer_to_plan(user: UserProfile, stripe_customer: stripe.Customer, stripe_plan_id: str,
-                                  seat_count: int, tax_percent: float) -> None:
+                                  seat_count: int, tax_percent: float, charge_automatically: bool) -> None:
     if extract_current_subscription(stripe_customer) is not None:
         # Most likely due to two people in the org going to the billing page,
         # and then both upgrading their plan. We don't send clients
@@ -212,6 +215,12 @@ def do_subscribe_customer_to_plan(user: UserProfile, stripe_customer: stripe.Cus
                              "but has an active subscription" % (stripe_customer.id, stripe_plan_id))
         raise BillingError('subscribing with existing subscription', BillingError.TRY_RELOADING)
     customer = Customer.objects.get(stripe_customer_id=stripe_customer.id)
+    if charge_automatically:
+        billing_method = 'charge_automatically'
+        days_until_due = None
+    else:
+        billing_method = 'send_invoice'
+        days_until_due = DEFAULT_INVOICE_DAYS_UNTIL_DUE
     # Note that there is a race condition here, where if two users upgrade at exactly the
     # same time, they will have two subscriptions, and get charged twice. We could try to
     # reduce the chance of it with a well-designed idempotency_key, but it's not easy since
@@ -222,7 +231,8 @@ def do_subscribe_customer_to_plan(user: UserProfile, stripe_customer: stripe.Cus
     # Otherwise we should expect it to throw a stripe.error.
     stripe_subscription = stripe.Subscription.create(
         customer=stripe_customer.id,
-        billing='charge_automatically',
+        billing=billing_method,
+        days_until_due=days_until_due,
         items=[{
             'plan': stripe_plan_id,
             'quantity': seat_count,
@@ -239,7 +249,8 @@ def do_subscribe_customer_to_plan(user: UserProfile, stripe_customer: stripe.Cus
             acting_user=user,
             event_type=RealmAuditLog.STRIPE_PLAN_CHANGED,
             event_time=timestamp_to_datetime(stripe_subscription.created),
-            extra_data=ujson.dumps({'plan': stripe_plan_id, 'quantity': seat_count}))
+            extra_data=ujson.dumps({'plan': stripe_plan_id, 'quantity': seat_count,
+                                    'billing_method': billing_method}))
 
         current_seat_count = get_seat_count(customer.realm)
         if seat_count != current_seat_count:
@@ -250,11 +261,14 @@ def do_subscribe_customer_to_plan(user: UserProfile, stripe_customer: stripe.Cus
                 requires_billing_update=True,
                 extra_data=ujson.dumps({'quantity': current_seat_count}))
 
-def process_initial_upgrade(user: UserProfile, plan: Plan, seat_count: int, stripe_token: str) -> None:
+def process_initial_upgrade(user: UserProfile, plan: Plan, seat_count: int,
+                            stripe_token: Optional[str]) -> None:
     customer = Customer.objects.filter(realm=user.realm).first()
     if customer is None:
         stripe_customer = do_create_customer(user, stripe_token=stripe_token)
-    else:
+    # elif instead of if since we want to avoid doing two round trips to
+    # stripe if we can
+    elif stripe_token is not None:
         stripe_customer = do_replace_payment_source(user, stripe_token)
     do_subscribe_customer_to_plan(
         user=user,
@@ -263,7 +277,8 @@ def process_initial_upgrade(user: UserProfile, plan: Plan, seat_count: int, stri
         seat_count=seat_count,
         # TODO: billing address details are passed to us in the request;
         # use that to calculate taxes.
-        tax_percent=0)
+        tax_percent=0,
+        charge_automatically=(stripe_token is not None))
     do_change_plan_type(user, Realm.STANDARD)
 
 def attach_discount_to_realm(user: UserProfile, percent_off: int) -> None:

corporate/tests/stripe_fixtures/upgrade_billing_by_invoice:Customer.create.1.json

@@ -0,0 +1,35 @@
+{
+  "account_balance": 0,
+  "created": 1542524016,
+  "currency": null,
+  "default_source": null,
+  "delinquent": false,
+  "description": "zulip (Zulip Dev)",
+  "discount": null,
+  "email": "hamlet@zulip.com",
+  "id": "cus_NORMALIZED0001",
+  "invoice_prefix": "NORMA01",
+  "livemode": false,
+  "metadata": {
+    "realm_id": "1",
+    "realm_str": "zulip"
+  },
+  "object": "customer",
+  "shipping": null,
+  "sources": {
+    "data": [],
+    "has_more": false,
+    "object": "list",
+    "total_count": 0,
+    "url": "/v1/customers/cus_NORMALIZED0001/sources"
+  },
+  "subscriptions": {
+    "data": [],
+    "has_more": false,
+    "object": "list",
+    "total_count": 0,
+    "url": "/v1/customers/cus_NORMALIZED0001/subscriptions"
+  },
+  "tax_info": null,
+  "tax_info_verification": null
+}

corporate/tests/stripe_fixtures/upgrade_billing_by_invoice:Customer.retrieve.1.json

@@ -0,0 +1,119 @@
+{
+  "account_balance": 0,
+  "created": 1542524016,
+  "currency": "usd",
+  "default_source": null,
+  "delinquent": false,
+  "description": "zulip (Zulip Dev)",
+  "discount": null,
+  "email": "hamlet@zulip.com",
+  "id": "cus_NORMALIZED0001",
+  "invoice_prefix": "NORMA01",
+  "livemode": false,
+  "metadata": {
+    "realm_id": "1",
+    "realm_str": "zulip"
+  },
+  "object": "customer",
+  "shipping": null,
+  "sources": {
+    "data": [],
+    "has_more": false,
+    "object": "list",
+    "total_count": 0,
+    "url": "/v1/customers/cus_NORMALIZED0001/sources"
+  },
+  "subscriptions": {
+    "data": [
+      {
+        "application_fee_percent": null,
+        "billing": "send_invoice",
+        "billing_cycle_anchor": 1542524017,
+        "cancel_at_period_end": false,
+        "canceled_at": null,
+        "created": 1542524017,
+        "current_period_end": 1574060017,
+        "current_period_start": 1542524017,
+        "customer": "cus_NORMALIZED0001",
+        "days_until_due": 30,
+        "default_source": null,
+        "discount": null,
+        "ended_at": null,
+        "id": "sub_NORMALIZED0001",
+        "items": {
+          "data": [
+            {
+              "created": 1542524017,
+              "id": "si_NORMALIZED0001",
+              "metadata": {},
+              "object": "subscription_item",
+              "plan": {
+                "active": true,
+                "aggregate_usage": null,
+                "amount": 8000,
+                "billing_scheme": "per_unit",
+                "created": 1539831971,
+                "currency": "usd",
+                "id": "plan_Do3xCvbzO89OsR",
+                "interval": "year",
+                "interval_count": 1,
+                "livemode": false,
+                "metadata": {},
+                "nickname": "annual",
+                "object": "plan",
+                "product": "prod_Do3x494SetTDpx",
+                "tiers": null,
+                "tiers_mode": null,
+                "transform_usage": null,
+                "trial_period_days": null,
+                "usage_type": "licensed"
+              },
+              "quantity": 123,
+              "subscription": "sub_NORMALIZED0001"
+            }
+          ],
+          "has_more": false,
+          "object": "list",
+          "total_count": 1,
+          "url": "/v1/subscription_items?subscription=sub_NORMALIZED0001"
+        },
+        "livemode": false,
+        "metadata": {},
+        "object": "subscription",
+        "plan": {
+          "active": true,
+          "aggregate_usage": null,
+          "amount": 8000,
+          "billing_scheme": "per_unit",
+          "created": 1539831971,
+          "currency": "usd",
+          "id": "plan_Do3xCvbzO89OsR",
+          "interval": "year",
+          "interval_count": 1,
+          "livemode": false,
+          "metadata": {},
+          "nickname": "annual",
+          "object": "plan",
+          "product": "prod_Do3x494SetTDpx",
+          "tiers": null,
+          "tiers_mode": null,
+          "transform_usage": null,
+          "trial_period_days": null,
+          "usage_type": "licensed"
+        },
+        "quantity": 123,
+        "start": 1542524017,
+        "status": "active",
+        "tax_percent": 0.0,
+        "trial_end": null,
+        "trial_start": null
+      }
+    ],
+    "has_more": false,
+    "object": "list",
+    "total_count": 1,
+    "url": "/v1/customers/cus_NORMALIZED0001/subscriptions"
+  },
+  "tax_info": null,
+  "tax_info_verification": null
+}

corporate/tests/stripe_fixtures/upgrade_billing_by_invoice:Customer.retrieve.2.json

@@ -0,0 +1,209 @@
+{
+  "account_balance": 0,
+  "created": 1542524016,
+  "currency": "usd",
+  "default_source": {
+    "ach_credit_transfer": {
+      "account_number": "test_c61c954f0ca8",
+      "bank_name": "TEST BANK",
+      "fingerprint": "NORMALIZED000001",
+      "refund_account_holder_name": null,
+      "refund_account_holder_type": null,
+      "refund_account_number": null,
+      "refund_routing_number": null,
+      "routing_number": "110000000",
+      "swift_code": "TSTEZ122"
+    },
+    "amount": null,
+    "client_secret": "src_client_secret_DzjdyQ9DrS7xsDJprt8u1VGU",
+    "created": 1542524018,
+    "currency": "usd",
+    "customer": "cus_NORMALIZED0001",
+    "flow": "receiver",
+    "id": "src_1DXkA2Gh0CmXqmnwvjBfz4VX",
+    "livemode": false,
+    "metadata": {},
+    "object": "source",
+    "owner": {
+      "address": null,
+      "email": "amount_0@stripe.com",
+      "name": null,
+      "phone": null,
+      "verified_address": null,
+      "verified_email": null,
+      "verified_name": null,
+      "verified_phone": null
+    },
+    "receiver": {
+      "address": "110000000-test_c61c954f0ca8",
+      "amount_charged": 0,
+      "amount_received": 0,
+      "amount_returned": 0,
+      "refund_attributes_method": "email",
+      "refund_attributes_status": "missing"
+    },
+    "statement_descriptor": null,
+    "status": "pending",
+    "type": "ach_credit_transfer",
+    "usage": "reusable"
+  },
+  "delinquent": false,
+  "description": "zulip (Zulip Dev)",
+  "discount": null,
+  "email": "hamlet@zulip.com",
+  "id": "cus_NORMALIZED0001",
+  "invoice_prefix": "NORMA01",
+  "livemode": false,
+  "metadata": {
+    "realm_id": "1",
+    "realm_str": "zulip"
+  },
+  "object": "customer",
+  "shipping": null,
+  "sources": {
+    "data": [
+      {
+        "ach_credit_transfer": {
+          "account_number": "test_c61c954f0ca8",
+          "bank_name": "TEST BANK",
+          "fingerprint": "NORMALIZED000001",
+          "refund_account_holder_name": null,
+          "refund_account_holder_type": null,
+          "refund_account_number": null,
+          "refund_routing_number": null,
+          "routing_number": "110000000",
+          "swift_code": "TSTEZ122"
+        },
+        "amount": null,
+        "client_secret": "src_client_secret_DzjdyQ9DrS7xsDJprt8u1VGU",
+        "created": 1542524018,
+        "currency": "usd",
+        "customer": "cus_NORMALIZED0001",
+        "flow": "receiver",
+        "id": "src_1DXkA2Gh0CmXqmnwvjBfz4VX",
+        "livemode": false,
+        "metadata": {},
+        "object": "source",
+        "owner": {
+          "address": null,
+          "email": "amount_0@stripe.com",
+          "name": null,
+          "phone": null,
+          "verified_address": null,
+          "verified_email": null,
+          "verified_name": null,
+          "verified_phone": null
+        },
+        "receiver": {
+          "address": "110000000-test_c61c954f0ca8",
+          "amount_charged": 0,
+          "amount_received": 0,
+          "amount_returned": 0,
+          "refund_attributes_method": "email",
+          "refund_attributes_status": "missing"
+        },
+        "statement_descriptor": null,
+        "status": "pending",
+        "type": "ach_credit_transfer",
+        "usage": "reusable"
+      }
+    ],
+    "has_more": false,
+    "object": "list",
+    "total_count": 1,
+    "url": "/v1/customers/cus_NORMALIZED0001/sources"
+  },
+  "subscriptions": {
+    "data": [
+      {
+        "application_fee_percent": null,
+        "billing": "send_invoice",
+        "billing_cycle_anchor": 1542524017,
+        "cancel_at_period_end": false,
+        "canceled_at": null,
+        "created": 1542524017,
+        "current_period_end": 1574060017,
+        "current_period_start": 1542524017,
+        "customer": "cus_NORMALIZED0001",
+        "days_until_due": 30,
+        "default_source": null,
+        "discount": null,
+        "ended_at": null,
+        "id": "sub_NORMALIZED0001",
+        "items": {
+          "data": [
+            {
+              "created": 1542524017,
+              "id": "si_NORMALIZED0001",
+              "metadata": {},
+              "object": "subscription_item",
+              "plan": {
+                "active": true,
+                "aggregate_usage": null,
+                "amount": 8000,
+                "billing_scheme": "per_unit",
+                "created": 1539831971,
+                "currency": "usd",
+                "id": "plan_Do3xCvbzO89OsR",
+                "interval": "year",
+                "interval_count": 1,
+                "livemode": false,
+                "metadata": {},
+                "nickname": "annual",
+                "object": "plan",
+                "product": "prod_Do3x494SetTDpx",
+                "tiers": null,
+                "tiers_mode": null,
+                "transform_usage": null,
+                "trial_period_days": null,
+                "usage_type": "licensed"
+              },
+              "quantity": 8,
+              "subscription": "sub_NORMALIZED0001"
+            }
+          ],
+          "has_more": false,
+          "object": "list",
+          "total_count": 1,
+          "url": "/v1/subscription_items?subscription=sub_NORMALIZED0001"
+        },
+        "livemode": false,
+        "metadata": {},
+        "object": "subscription",
+        "plan": {
+          "active": true,
+          "aggregate_usage": null,
+          "amount": 8000,
+          "billing_scheme": "per_unit",
+          "created": 1539831971,
+          "currency": "usd",
+          "id": "plan_Do3xCvbzO89OsR",
+          "interval": "year",
+          "interval_count": 1,
+          "livemode": false,
+          "metadata": {},
+          "nickname": "annual",
+          "object": "plan",
+          "product": "prod_Do3x494SetTDpx",
+          "tiers": null,
+          "tiers_mode": null,
+          "transform_usage": null,
+          "trial_period_days": null,
+          "usage_type": "licensed"
+        },
+        "quantity": 8,
+        "start": 1542524018,
+        "status": "active",
+        "tax_percent": 0.0,
+        "trial_end": null,
+        "trial_start": null
+      }
+    ],
+    "has_more": false,
+    "object": "list",
+    "total_count": 1,
+    "url": "/v1/customers/cus_NORMALIZED0001/subscriptions"
+  },
+  "tax_info": null,
+  "tax_info_verification": null
+}

corporate/tests/stripe_fixtures/upgrade_billing_by_invoice:Invoice.list.1.json

@@ -0,0 +1,98 @@
+{
+  "data": [
+    {
+      "amount_due": 984000,
+      "amount_paid": 0,
+      "amount_remaining": 984000,
+      "application_fee": null,
+      "attempt_count": 0,
+      "attempted": false,
+      "auto_advance": true,
+      "billing": "send_invoice",
+      "billing_reason": "subscription_create",
+      "charge": null,
+      "currency": "usd",
+      "customer": "cus_NORMALIZED0001",
+      "date": 1542524017,
+      "default_source": null,
+      "description": "",
+      "discount": null,
+      "due_date": 1545116017,
+      "ending_balance": null,
+      "finalized_at": null,
+      "hosted_invoice_url": null,
+      "id": "in_1DXkA1Gh0CmXqmnwNApgkOR1",
+      "invoice_pdf": null,
+      "lines": {
+        "data": [
+          {
+            "amount": 984000,
+            "currency": "usd",
+            "description": "123 user \u00d7 Zulip Cloud Premium (at $80.00 / year)",
+            "discountable": true,
+            "id": "sli_NORMALIZED0001",
+            "livemode": false,
+            "metadata": {},
+            "object": "line_item",
+            "period": {
+              "end": 1574060017,
+              "start": 1542524017
+            },
+            "plan": {
+              "active": true,
+              "aggregate_usage": null,
+              "amount": 8000,
+              "billing_scheme": "per_unit",
+              "created": 1539831971,
+              "currency": "usd",
+              "id": "plan_Do3xCvbzO89OsR",
+              "interval": "year",
+              "interval_count": 1,
+              "livemode": false,
+              "metadata": {},
+              "nickname": "annual",
+              "object": "plan",
+              "product": "prod_Do3x494SetTDpx",
+              "tiers": null,
+              "tiers_mode": null,
+              "transform_usage": null,
+              "trial_period_days": null,
+              "usage_type": "licensed"
+            },
+            "proration": false,
+            "quantity": 123,
+            "subscription": "sub_NORMALIZED0001",
+            "subscription_item": "si_NORMALIZED0001",
+            "type": "subscription"
+          }
+        ],
+        "has_more": false,
+        "object": "list",
+        "total_count": 1,
+        "url": "/v1/invoices/in_1DXkA1Gh0CmXqmnwNApgkOR1/lines"
+      },
+      "livemode": false,
+      "metadata": {},
+      "next_payment_attempt": null,
+      "number": "NORMALI-0001",
+      "object": "invoice",
+      "paid": false,
+      "payment_intent": null,
+      "period_end": 1542524017,
+      "period_start": 1542524017,
+      "receipt_number": null,
+      "starting_balance": 0,
+      "statement_descriptor": null,
+      "status": "draft",
+      "subscription": "sub_NORMALIZED0001",
+      "subtotal": 984000,
+      "tax": 0,
+      "tax_percent": 0.0,
+      "total": 984000,
+      "webhooks_delivered_at": 1542524017
+    }
+  ],
+  "has_more": false,
+  "object": "list",
+  "url": "/v1/invoices"
+}

corporate/tests/stripe_fixtures/upgrade_billing_by_invoice:Subscription.create.1.json

@@ -0,0 +1,83 @@
+{
+  "application_fee_percent": null,
+  "billing": "send_invoice",
+  "billing_cycle_anchor": 1542524017,
+  "cancel_at_period_end": false,
+  "canceled_at": null,
+  "created": 1542524017,
+  "current_period_end": 1574060017,
+  "current_period_start": 1542524017,
+  "customer": "cus_NORMALIZED0001",
+  "days_until_due": 30,
+  "default_source": null,
+  "discount": null,
+  "ended_at": null,
+  "id": "sub_NORMALIZED0001",
+  "items": {
+    "data": [
+      {
+        "created": 1542524017,
+        "id": "si_NORMALIZED0001",
+        "metadata": {},
+        "object": "subscription_item",
+        "plan": {
+          "active": true,
+          "aggregate_usage": null,
+          "amount": 8000,
+          "billing_scheme": "per_unit",
+          "created": 1539831971,
+          "currency": "usd",
+          "id": "plan_Do3xCvbzO89OsR",
+          "interval": "year",
+          "interval_count": 1,
+          "livemode": false,
+          "metadata": {},
+          "nickname": "annual",
+          "object": "plan",
+          "product": "prod_Do3x494SetTDpx",
+          "tiers": null,
+          "tiers_mode": null,
+          "transform_usage": null,
+          "trial_period_days": null,
+          "usage_type": "licensed"
+        },
+        "quantity": 123,
+        "subscription": "sub_NORMALIZED0001"
+      }
+    ],
+    "has_more": false,
+    "object": "list",
+    "total_count": 1,
+    "url": "/v1/subscription_items?subscription=sub_NORMALIZED0001"
+  },
+  "livemode": false,
+  "metadata": {},
+  "object": "subscription",
+  "plan": {
+    "active": true,
+    "aggregate_usage": null,
+    "amount": 8000,
+    "billing_scheme": "per_unit",
+    "created": 1539831971,
+    "currency": "usd",
+    "id": "plan_Do3xCvbzO89OsR",
+    "interval": "year",
+    "interval_count": 1,
+    "livemode": false,
+    "metadata": {},
+    "nickname": "annual",
+    "object": "plan",
+    "product": "prod_Do3x494SetTDpx",
+    "tiers": null,
+    "tiers_mode": null,
+    "transform_usage": null,
+    "trial_period_days": null,
+    "usage_type": "licensed"
+  },
+  "quantity": 123,
+  "start": 1542524017,
+  "status": "active",
+  "tax_percent": 0.0,
+  "trial_end": null,
+  "trial_start": null
+}

corporate/tests/stripe_fixtures/upgrade_billing_by_invoice:Subscription.save.1.json

@@ -0,0 +1,83 @@
+{
+  "application_fee_percent": null,
+  "billing": "send_invoice",
+  "billing_cycle_anchor": 1542524017,
+  "cancel_at_period_end": false,
+  "canceled_at": null,
+  "created": 1542524017,
+  "current_period_end": 1574060017,
+  "current_period_start": 1542524017,
+  "customer": "cus_NORMALIZED0001",
+  "days_until_due": 30,
+  "default_source": null,
+  "discount": null,
+  "ended_at": null,
+  "id": "sub_NORMALIZED0001",
+  "items": {
+    "data": [
+      {
+        "created": 1542524017,
+        "id": "si_NORMALIZED0001",
+        "metadata": {},
+        "object": "subscription_item",
+        "plan": {
+          "active": true,
+          "aggregate_usage": null,
+          "amount": 8000,
+          "billing_scheme": "per_unit",
+          "created": 1539831971,
+          "currency": "usd",
+          "id": "plan_Do3xCvbzO89OsR",
+          "interval": "year",
+          "interval_count": 1,
+          "livemode": false,
+          "metadata": {},
+          "nickname": "annual",
+          "object": "plan",
+          "product": "prod_Do3x494SetTDpx",
+          "tiers": null,
+          "tiers_mode": null,
+          "transform_usage": null,
+          "trial_period_days": null,
+          "usage_type": "licensed"
+        },
+        "quantity": 8,
+        "subscription": "sub_NORMALIZED0001"
+      }
+    ],
+    "has_more": false,
+    "object": "list",
+    "total_count": 1,
+    "url": "/v1/subscription_items?subscription=sub_NORMALIZED0001"
+  },
+  "livemode": false,
+  "metadata": {},
+  "object": "subscription",
+  "plan": {
+    "active": true,
+    "aggregate_usage": null,
+    "amount": 8000,
+    "billing_scheme": "per_unit",
+    "created": 1539831971,
+    "currency": "usd",
+    "id": "plan_Do3xCvbzO89OsR",
+    "interval": "year",
+    "interval_count": 1,
+    "livemode": false,
+    "metadata": {},
+    "nickname": "annual",
+    "object": "plan",
+    "product": "prod_Do3x494SetTDpx",
+    "tiers": null,
+    "tiers_mode": null,
+    "transform_usage": null,
+    "trial_period_days": null,
+    "usage_type": "licensed"
+  },
+  "quantity": 8,
+  "start": 1542524018,
+  "status": "active",
+  "tax_percent": 0.0,
+  "trial_end": null,
+  "trial_start": null
+}

corporate/tests/test_stripe.py

@@ -26,7 +26,8 @@ from corporate.lib.stripe import catch_stripe_errors, \
     do_subscribe_customer_to_plan, attach_discount_to_realm, \
     get_seat_count, extract_current_subscription, sign_string, unsign_string, \
     get_next_billing_log_entry, run_billing_processor_one_step, \
-    BillingError, StripeCardError, StripeConnectionError, stripe_get_customer
+    BillingError, StripeCardError, StripeConnectionError, stripe_get_customer, \
+    DEFAULT_INVOICE_DAYS_UNTIL_DUE, MIN_INVOICED_SEAT_COUNT
 from corporate.models import Customer, Plan, Coupon, BillingProcessor
 import corporate.urls
 
@@ -206,6 +207,13 @@ class Kandra(object):
     def __eq__(self, other: Any) -> bool:
         return True
 
+def process_all_billing_log_entries() -> None:
+    assert not RealmAuditLog.objects.get(pk=1).requires_billing_update
+    processor = BillingProcessor.objects.create(
+        log_row=RealmAuditLog.objects.get(pk=1), realm=None, state=BillingProcessor.DONE)
+    while run_billing_processor_one_step(processor):
+        pass
+
 class StripeTest(ZulipTestCase):
     @mock_stripe("Product.create", "Plan.create", "Coupon.create", generate=False)
     def setUp(self, mock3: Mock, mock2: Mock, mock1: Mock) -> None:
@@ -467,6 +475,30 @@ class StripeTest(ZulipTestCase):
         self.assert_in_success_response(["Upgrade to Zulip Standard"], response)
         self.assertEqual(response['error_description'], 'tampered plan')
 
+    def test_upgrade_with_insufficient_invoiced_seat_count(self) -> None:
+        self.login(self.example_email("hamlet"))
+        # Test invoicing for less than MIN_INVOICED_SEAT_COUNT
+        response = self.client_post("/upgrade/", {
+            'invoiced_seat_count': self.quantity,
+            'signed_seat_count': self.signed_seat_count,
+            'salt': self.salt,
+            'plan': Plan.CLOUD_ANNUAL
+        })
+        self.assert_in_success_response(["Upgrade to Zulip Standard",
+                                         "at least %d users" % (MIN_INVOICED_SEAT_COUNT,)], response)
+        self.assertEqual(response['error_description'], 'lowball seat count')
+        # Test invoicing for less than your user count
+        with patch("corporate.views.MIN_INVOICED_SEAT_COUNT", 3):
+            response = self.client_post("/upgrade/", {
+                'invoiced_seat_count': self.quantity - 1,
+                'signed_seat_count': self.signed_seat_count,
+                'salt': self.salt,
+                'plan': Plan.CLOUD_ANNUAL
+            })
+        self.assert_in_success_response(["Upgrade to Zulip Standard",
+                                         "at least %d users" % (self.quantity,)], response)
+        self.assertEqual(response['error_description'], 'lowball seat count')
+
     @patch("corporate.lib.stripe.billing_logger.error")
     def test_upgrade_with_uncaught_exception(self, mock1: Mock) -> None:
         self.login(self.example_email("hamlet"))
@@ -481,6 +513,69 @@ class StripeTest(ZulipTestCase):
                                          "Something went wrong. Please contact"], response)
         self.assertEqual(response['error_description'], 'uncaught exception during upgrade')
 
+    @mock_stripe("Customer.create", "Subscription.create", "Subscription.save",
+                 "Customer.retrieve", "Invoice.list")
+    def test_upgrade_billing_by_invoice(self, mock5: Mock, mock4: Mock, mock3: Mock,
+                                        mock2: Mock, mock1: Mock) -> None:
+        user = self.example_user("hamlet")
+        self.login(user.email)
+        self.client_post("/upgrade/", {
+            'invoiced_seat_count': 123,
+            'signed_seat_count': self.signed_seat_count,
+            'salt': self.salt,
+            'plan': Plan.CLOUD_ANNUAL})
+        process_all_billing_log_entries()
+
+        # Check that we correctly created a Customer in Stripe
+        stripe_customer = stripe_get_customer(Customer.objects.get(realm=user.realm).stripe_customer_id)
+        self.assertEqual(stripe_customer.email, user.email)
+        # It can take a second for Stripe to attach the source to the
+        # customer, and in particular it may not be attached at the time
+        # stripe_get_customer is called above, causing test flakes.
+        # So commenting the next line out, but leaving it here so future readers know what
+        # is supposed to happen here (e.g. the default_source is not None as it would be if
+        # we had not added a Subscription).
+        # self.assertEqual(stripe_customer.default_source.type, 'ach_credit_transfer')
+
+        # Check that we correctly created a Subscription in Stripe
+        stripe_subscription = extract_current_subscription(stripe_customer)
+        self.assertEqual(stripe_subscription.billing, 'send_invoice')
+        self.assertEqual(stripe_subscription.days_until_due, DEFAULT_INVOICE_DAYS_UNTIL_DUE)
+        self.assertEqual(stripe_subscription.plan.id,
+                         Plan.objects.get(nickname=Plan.CLOUD_ANNUAL).stripe_plan_id)
+        self.assertEqual(stripe_subscription.quantity, get_seat_count(user.realm))
+        self.assertEqual(stripe_subscription.status, 'active')
+        # Check that we correctly created an initial Invoice in Stripe
+        for stripe_invoice in stripe.Invoice.list(customer=stripe_customer.id, limit=1):
+            self.assertTrue(stripe_invoice.auto_advance)
+            self.assertEqual(stripe_invoice.billing, 'send_invoice')
+            self.assertEqual(stripe_invoice.billing_reason, 'subscription_create')
+            # Transitions to 'open' after 1-2 hours
+            self.assertEqual(stripe_invoice.status, 'draft')
+            # Very important. Check that we're invoicing for 123, and not get_seat_count
+            self.assertEqual(stripe_invoice.amount_due, 8000*123)
+
+        # Check that we correctly updated Realm
+        realm = get_realm("zulip")
+        self.assertTrue(realm.has_seat_based_plan)
+        self.assertEqual(realm.plan_type, Realm.STANDARD)
+        # Check that we created a Customer in Zulip
+        self.assertEqual(1, Customer.objects.filter(stripe_customer_id=stripe_customer.id,
+                                                    realm=realm).count())
+        # Check that RealmAuditLog has STRIPE_PLAN_QUANTITY_RESET, and doesn't have STRIPE_CARD_CHANGED
+        audit_log_entries = list(RealmAuditLog.objects.order_by('-id')
+                                 .values_list('event_type', 'event_time',
+                                              'requires_billing_update')[:4])[::-1]
+        self.assertEqual(audit_log_entries, [
+            (RealmAuditLog.STRIPE_CUSTOMER_CREATED, timestamp_to_datetime(stripe_customer.created), False),
+            (RealmAuditLog.STRIPE_PLAN_CHANGED, timestamp_to_datetime(stripe_subscription.created), False),
+            (RealmAuditLog.STRIPE_PLAN_QUANTITY_RESET, timestamp_to_datetime(stripe_subscription.created), True),
+            (RealmAuditLog.REALM_PLAN_TYPE_CHANGED, Kandra(), False),
+        ])
+        self.assertEqual(ujson.loads(RealmAuditLog.objects.filter(
+            event_type=RealmAuditLog.STRIPE_PLAN_QUANTITY_RESET).values_list('extra_data', flat=True).first()),
+            {'quantity': self.quantity})
+
     @patch("stripe.Customer.retrieve", side_effect=mock_customer_with_subscription)
     def test_redirect_for_billing_home(self, mock_customer_with_subscription: Mock) -> None:
         user = self.example_user("iago")
@@ -532,7 +627,7 @@ class StripeTest(ZulipTestCase):
         with self.assertRaisesRegex(BillingError, 'subscribing with existing subscription'):
             do_subscribe_customer_to_plan(self.example_user("iago"),
                                           mock_customer_with_subscription(),
-                                          self.stripe_plan_id, self.quantity, 0)
+                                          self.stripe_plan_id, self.quantity, 0, True)
 
     def test_sign_string(self) -> None:
         string = "abc"

corporate/views.py

@@ -18,7 +18,8 @@ from zerver.models import UserProfile, Realm
 from corporate.lib.stripe import STRIPE_PUBLISHABLE_KEY, \
     stripe_get_customer, upcoming_invoice_total, get_seat_count, \
     extract_current_subscription, process_initial_upgrade, sign_string, \
-    unsign_string, BillingError, process_downgrade, do_replace_payment_source
+    unsign_string, BillingError, process_downgrade, do_replace_payment_source, \
+    MIN_INVOICED_SEAT_COUNT
 from corporate.models import Customer, Plan
 
 billing_logger = logging.getLogger('corporate.stripe')
@@ -56,7 +57,14 @@ def initial_upgrade(request: HttpRequest) -> HttpResponse:
         try:
             plan, seat_count = unsign_and_check_upgrade_parameters(
                 user, request.POST['plan'], request.POST['signed_seat_count'], request.POST['salt'])
-            process_initial_upgrade(user, plan, seat_count, request.POST['stripeToken'])
+            if 'invoiced_seat_count' in request.POST:
+                min_required_seat_count = max(seat_count, MIN_INVOICED_SEAT_COUNT)
+                if int(request.POST['invoiced_seat_count']) < min_required_seat_count:
+                    raise BillingError(
+                        'lowball seat count',
+                        "You must invoice for at least %d users." % (min_required_seat_count,))
+                seat_count = int(request.POST['invoiced_seat_count'])
+            process_initial_upgrade(user, plan, seat_count, request.POST.get('stripeToken', None))
         except BillingError as e:
             error_message = e.message
             error_description = e.description
@@ -129,8 +137,12 @@ def billing_home(request: HttpRequest) -> HttpResponse:
         renewal_amount = 0
 
     payment_method = None
-    if stripe_customer.default_source is not None:
+    stripe_source = stripe_customer.default_source
-        payment_method = "Card ending in %(last4)s" % {'last4': stripe_customer.default_source.last4}
+    if stripe_source is not None:
+        if stripe_source.object == 'card':
+            # To fix mypy error, set Customer.default_source: Union[Source, Card] in stubs and debug
+            payment_method = "Card ending in %(last4)s" % \
+                             {'last4': stripe_source.last4}  # type: ignore # see above
 
     context.update({
         'plan_name': plan_name,

stubs/stripe/__init__.pyi

@@ -8,7 +8,7 @@ from typing import Optional, Any, Dict, List, Union
 api_key: Optional[str]
 
 class Customer:
-    default_source: Card
+    default_source: Source
     created: int
     id: str
     source: str
@@ -43,7 +43,12 @@ class Customer:
 
 
 class Invoice:
+    auto_advance: bool
     amount_due: int
+    billing: str
+    billing_reason: str
+    default_source: Source
+    status: str
     total: int
 
     @staticmethod
@@ -51,16 +56,22 @@ class Invoice:
                  subscription_items: List[Dict[str, Union[str, int]]]=...) -> Invoice:
         ...
 
+    @staticmethod
+    def list(customer: str=..., limit: Optional[int]=...) -> List[Invoice]:
+        ...
+
 class Subscription:
     created: int
     status: str
     canceled_at: int
     cancel_at_period_end: bool
+    days_until_due: Optional[int]
     proration_date: int
     quantity: int
 
     @staticmethod
-    def create(customer: str=..., billing: str=..., items: List[Dict[str, Any]]=...,
+    def create(customer: str=..., billing: str=..., days_until_due: Optional[int]=...,
+               items: List[Dict[str, Any]]=...,
                prorate: bool=..., tax_percent: float=...) -> Subscription:
         ...
 
@@ -68,9 +79,15 @@ class Subscription:
     def save(subscription: Subscription, idempotency_key: str=...) -> Subscription:
         ...
 
+class Source:
+    id: str
+    object: str
+    type: str
+
 class Card:
     id: str
     last4: str
+    object: str
 
 class Plan:
     id: str