Added discount model (dj-stripe#1751)

* Added internal model InvoiceOrLineItem

InvoiceOrLineItem model is similar to the DjstripePaymentMethod model and
acts as a wrapper around the InvoiceItem and LineItem models.

This was done because Discount.invoice_item model field can receive
either of InvoiceItem or LineItem objects.

* Added InvoiceOrLineItemForeignKey custom model field

InvoiceOrLineItemForeignKey is like the PaymentMethodForeignKey to be able to
deal with both InvoiceItem and LineItem models whichever is returned as the
Discounts invoice_item field's value.

* Added Discount Model

* Exposed Discount model on the Admin

* Updated _handle_crud_like_event to allow syncing of discount.* events

This was done because Stripe doesn't allow direct retrieval
of Discount objects.

* Fixed Discount Event Fixtures

* Fixed corner case in Event.customer prop

It could be possible that the json key
may have been expanded using expand_fields
attribute and hence also handled that case.

* Updated Changelog

* Fix Formatting Errors

djstripe/admin/admin.py

@@ -248,6 +248,30 @@ def get_queryset(self, request):
         )
 
 
+@admin.register(models.Discount)
+class DiscountAdmin(ReadOnlyMixin, StripeModelAdmin):
+    list_display = (
+        "customer",
+        "coupon",
+        "invoice_item",
+        "promotion_code",
+        "subscription",
+    )
+    list_filter = ("customer", "start", "end", "promotion_code", "coupon")
+
+    def get_actions(self, request):
+        """
+        Returns _resync_instances only for
+        models with a defined model.stripe_class.retrieve
+        """
+        actions = super().get_actions(request)
+
+        # remove "_sync_all_instances" as Discounts cannot be listed
+        actions.pop("_sync_all_instances", None)
+
+        return actions
+
+
 @admin.register(models.Dispute)
 class DisputeAdmin(ReadOnlyMixin, StripeModelAdmin):
     list_display = ("reason", "status", "amount", "currency", "is_charge_refundable")

djstripe/enums.py

@@ -414,6 +414,12 @@ class InvoiceStatus(Enum):
     void = _("Void")
 
 
+class InvoiceorLineItemType(Enum):
+    invoice_item = _("Invoice Item")
+    line_item = _("Line Item")
+    unsupported = _("Unsupported")
+
+
 class IntentUsage(Enum):
     on_session = _("On session")
     off_session = _("Off session")

djstripe/event_handlers.py

@@ -408,9 +408,14 @@ def _handle_crud_like_event(
         if event.parts[:2] == ["account", "external_account"] and stripe_account:
             kwargs["account"] = models.Account._get_or_retrieve(id=stripe_account)
 
-        data = target_cls(**kwargs).api_retrieve(
-            stripe_account=stripe_account, api_key=event.default_api_key
-        )
+        # Stripe doesn't allow retrieval of Discount Objects
+        if target_cls not in (models.Discount,):
+            data = target_cls(**kwargs).api_retrieve(
+                stripe_account=stripe_account, api_key=event.default_api_key
+            )
+        else:
+            data = data.get("object")
+
         # create or update the object from the retrieved Stripe Data
         obj = target_cls.sync_from_stripe_data(data, api_key=event.default_api_key)
 

djstripe/fields.py

@@ -59,6 +59,12 @@ def __init__(self, **kwargs):
         super().__init__(**kwargs)
 
 
+class InvoiceOrLineItemForeignKey(models.ForeignKey):
+    def __init__(self, **kwargs):
+        kwargs.setdefault("to", "InvoiceOrLineItem")
+        super().__init__(**kwargs)
+
+
 class StripePercentField(FieldDeconstructMixin, models.DecimalField):
     """A field used to define a percent according to djstripe logic."""
 

djstripe/migrations/0017_invoiceorlineitem.py

@@ -0,0 +1,32 @@
+# Generated by Django 3.2.13 on 2022-07-09 08:04
+
+import django.db.models.deletion
+from django.conf import settings
+from django.db import migrations, models
+
+import djstripe.enums
+import djstripe.fields
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("djstripe", "0016_alter_payout_destination"),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name="InvoiceOrLineItem",
+            fields=[
+                (
+                    "id",
+                    models.CharField(max_length=255, primary_key=True, serialize=False),
+                ),
+                (
+                    "type",
+                    djstripe.fields.StripeEnumField(
+                        enum=djstripe.enums.InvoiceorLineItemType, max_length=12
+                    ),
+                ),
+            ],
+        ),
+    ]

djstripe/migrations/0018_discount.py

@@ -0,0 +1,130 @@
+# Generated by Django 3.2.16 on 2023-01-28 06:04
+
+import django.db.models.deletion
+from django.conf import settings
+from django.db import migrations, models
+
+import djstripe.fields
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("djstripe", "0017_invoiceorlineitem"),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name="Discount",
+            fields=[
+                ("djstripe_created", models.DateTimeField(auto_now_add=True)),
+                ("djstripe_updated", models.DateTimeField(auto_now=True)),
+                (
+                    "djstripe_id",
+                    models.BigAutoField(
+                        primary_key=True, serialize=False, verbose_name="ID"
+                    ),
+                ),
+                ("id", djstripe.fields.StripeIdField(max_length=255, unique=True)),
+                (
+                    "livemode",
+                    models.BooleanField(
+                        blank=True,
+                        default=None,
+                        help_text="Null here indicates that the livemode status is unknown or was previously unrecorded. Otherwise, this field indicates whether this record comes from Stripe test mode or live mode operation.",
+                        null=True,
+                    ),
+                ),
+                ("created", djstripe.fields.StripeDateTimeField(blank=True, null=True)),
+                ("metadata", djstripe.fields.JSONField(blank=True, null=True)),
+                (
+                    "description",
+                    models.TextField(
+                        blank=True, help_text="A description of this object.", null=True
+                    ),
+                ),
+                ("coupon", djstripe.fields.JSONField(blank=True, null=True)),
+                ("end", djstripe.fields.StripeDateTimeField(blank=True, null=True)),
+                (
+                    "promotion_code",
+                    models.CharField(
+                        blank=True,
+                        help_text="The promotion code applied to create this discount.",
+                        max_length=255,
+                    ),
+                ),
+                ("start", djstripe.fields.StripeDateTimeField(blank=True, null=True)),
+                (
+                    "checkout_session",
+                    djstripe.fields.StripeForeignKey(
+                        blank=True,
+                        help_text="The Checkout session that this coupon is applied to, if it is applied to a particular session in payment mode. Will not be present for subscription mode.",
+                        null=True,
+                        on_delete=django.db.models.deletion.CASCADE,
+                        to="djstripe.session",
+                        to_field=settings.DJSTRIPE_FOREIGN_KEY_TO_FIELD,
+                    ),
+                ),
+                (
+                    "customer",
+                    djstripe.fields.StripeForeignKey(
+                        blank=True,
+                        help_text="The ID of the customer associated with this discount.",
+                        null=True,
+                        on_delete=django.db.models.deletion.CASCADE,
+                        related_name="customer_discounts",
+                        to="djstripe.customer",
+                        to_field=settings.DJSTRIPE_FOREIGN_KEY_TO_FIELD,
+                    ),
+                ),
+                (
+                    "djstripe_owner_account",
+                    djstripe.fields.StripeForeignKey(
+                        blank=True,
+                        help_text="The Stripe Account this object belongs to.",
+                        null=True,
+                        on_delete=django.db.models.deletion.CASCADE,
+                        to="djstripe.account",
+                        to_field=settings.DJSTRIPE_FOREIGN_KEY_TO_FIELD,
+                    ),
+                ),
+                (
+                    "invoice",
+                    djstripe.fields.StripeForeignKey(
+                        blank=True,
+                        help_text="The invoice that the discount’s coupon was applied to, if it was applied directly to a particular invoice.",
+                        null=True,
+                        on_delete=django.db.models.deletion.CASCADE,
+                        related_name="invoice_discounts",
+                        to="djstripe.invoice",
+                        to_field=settings.DJSTRIPE_FOREIGN_KEY_TO_FIELD,
+                    ),
+                ),
+                (
+                    "invoice_item",
+                    djstripe.fields.InvoiceOrLineItemForeignKey(
+                        blank=True,
+                        help_text="The invoice item id (or invoice line item id for invoice line items of type=‘subscription’) that the discount’s coupon was applied to, if it was applied directly to a particular invoice item or invoice line item.",
+                        null=True,
+                        on_delete=django.db.models.deletion.CASCADE,
+                        to="djstripe.invoiceorlineitem",
+                    ),
+                ),
+                (
+                    "subscription",
+                    djstripe.fields.StripeForeignKey(
+                        blank=True,
+                        help_text="The subscription that this coupon is applied to, if it is applied to a particular subscription.",
+                        null=True,
+                        on_delete=django.db.models.deletion.CASCADE,
+                        related_name="subscription_discounts",
+                        to="djstripe.subscription",
+                        to_field=settings.DJSTRIPE_FOREIGN_KEY_TO_FIELD,
+                    ),
+                ),
+            ],
+            options={
+                "get_latest_by": "created",
+                "abstract": False,
+            },
+        ),
+    ]

djstripe/models/__init__.py

@@ -3,8 +3,10 @@
 from .base import IdempotencyKey, StripeModel
 from .billing import (
     Coupon,
+    Discount,
     Invoice,
     InvoiceItem,
+    InvoiceOrLineItem,
     LineItem,
     Plan,
     ShippingRate,
@@ -66,6 +68,7 @@
     "CountrySpec",
     "Coupon",
     "Customer",
+    "Discount",
     "Dispute",
     "DjstripePaymentMethod",
     "Event",
@@ -76,6 +79,7 @@
     "Invoice",
     "InvoiceItem",
     "LineItem",
+    "InvoiceOrLineItem",
     "Mandate",
     "Order",
     "PaymentIntent",

djstripe/models/base.py

@@ -439,7 +439,7 @@ def _stripe_object_field_to_foreign_key(
         :type stripe_account: string
         :return:
         """
-        from djstripe.models import DjstripePaymentMethod
+        from djstripe.models import DjstripePaymentMethod, InvoiceOrLineItem
 
         field_data = None
         field_name = field.name
@@ -451,8 +451,8 @@ def _stripe_object_field_to_foreign_key(
         if current_ids is None:
             current_ids = set()
 
-        if issubclass(field.related_model, StripeModel) or issubclass(
-            field.related_model, DjstripePaymentMethod
+        if issubclass(
+            field.related_model, (StripeModel, DjstripePaymentMethod, InvoiceOrLineItem)
         ):
             if field_name in manipulated_data:
                 raw_field_data = manipulated_data.get(field_name)