feat: New Paginated generic to be used as a wrapped for paginated res…

…ults (#642)

docs/guide/pagination.md

@@ -12,20 +12,306 @@ An interface for limit/offset pagination can be use for basic pagination needs:
 @strawberry_django.type(models.Fruit, pagination=True)
 class Fruit:
     name: auto
+
+
+@strawberry.type
+class Query:
+    fruits: list[Fruit] = strawberry_django.field()
+```
+
+Would produce the following schema:
+
+```graphql title="schema.graphql"
+type Fruit {
+  name: String!
+}
+
+input OffsetPaginationInput {
+  offset: Int! = 0
+  limit: Int = null
+}
+
+type Query {
+  fruits(pagination: OffsetPaginationInput): [Fruit!]!
+}
 ```
 
+And can be queried like:
+
 ```graphql title="schema.graphql"
 query {
   fruits(pagination: { offset: 0, limit: 2 }) {
     name
-    color
   }
 }
 ```
 
-There is not default limit defined. All elements are returned if no pagination limit is defined.
+The `pagination` argument can be given to the type, which will enforce the pagination
+argument every time the field is annotated as a list, but you can also give it directly
+to the field for more control, like:
+
+```python title="types.py"
+@strawberry_django.type(models.Fruit)
+class Fruit:
+    name: auto
+
+
+@strawberry.type
+class Query:
+    fruits: list[Fruit] = strawberry_django.field(pagination=True)
+```
+
+Which will produce the exact same schema.
+
+### Default limit for pagination
+
+The default limit for pagination is set to `100`. This can be changed in the
+[strawberry django settings](./settings.md) to increase or decrease that number,
+or even set to `None` to set it to unlimited.
+
+To configure it on a per field basis, you can define your own `OffsetPaginationInput`
+subclass and modify its default value, like:
+
+```python
+@strawberry.input
+def MyOffsetPaginationInput(OffsetPaginationInput):
+    limit: int = 250
+
+
+# Pass it to the pagination argument when defining the type
+@strawberry_django.type(models.Fruit, pagination=MyOffsetPaginationInput)
+class Fruit:
+    ...
+
+
+@strawberry.type
+class Query:
+    # Or pass it to the pagination argument when defining the field
+    fruits: list[Fruit] = strawberry_django.field(pagination=MyOffsetPaginationInput)
+```
+
+## OffsetPaginated Generic
+
+For more complex pagination needs, you can use the `OffsetPaginated` generic, which alongside
+the `pagination` argument, will wrap the results in an object that contains the results
+and the pagination information, together with the `totalCount` of elements excluding pagination.
+
+```python title="types.py"
+from strawberry_django.pagination import OffsetPaginated
+
+
+@strawberry_django.type(models.Fruit)
+class Fruit:
+    name: auto
+
+
+@strawberry.type
+class Query:
+    fruits: OffsetPaginated[Fruit] = strawberry_django.offset_paginated()
+```
+
+Would produce the following schema:
+
+```graphql title="schema.graphql"
+type Fruit {
+  name: String!
+}
+
+type PaginationInfo {
+  limit: Int = null
+  offset: Int!
+}
+
+type FruitOffsetPaginated {
+  pageInfo: PaginationInfo!
+  totalCount: Int!
+  results: [Fruit]!
+}
+
+input OffsetPaginationInput {
+  offset: Int! = 0
+  limit: Int = null
+}
+
+type Query {
+  fruits(pagination: OffsetPaginationInput): [FruitOffsetPaginated!]!
+}
+```
+
+Which can be queried like:
+
+```graphql title="schema.graphql"
+query {
+  fruits(pagination: { offset: 0, limit: 2 }) {
+    totalCount
+    pageInfo {
+      limit
+      offset
+    }
+    results {
+      name
+    }
+  }
+}
+```
+
+> [!NOTE]
+> OffsetPaginated follow the same rules for the default pagination limit, and can be configured
+> in the same way as explained above.
+
+### Customizing queryset resolver
+
+It is possible to define a custom resolver for the queryset to either provide a custom
+queryset for it, or even to receive extra arguments alongside the pagination arguments.
+
+Suppose we want to pre-filter a queryset of fruits for only available ones,
+while also adding [ordering](./ordering.md) to it. This can be achieved with:
+
+```python title="types.py"
+
+@strawberry_django.type(models.Fruit)
+class Fruit:
+    name: auto
+    price: auto
+
+
+@strawberry_django.order(models.Fruit)
+class FruitOrder:
+    name: auto
+    price: auto
+
+
+@strawberry.type
+class Query:
+    @strawberry_django.offset_paginated(OffsetPaginated[Fruit], order=order)
+    def fruits(self, only_available: bool = True) -> QuerySet[Fruit]:
+        queryset = models.Fruit.objects.all()
+        if only_available:
+            queryset = queryset.filter(available=True)
+
+        return queryset
+```
+
+This would produce the following schema:
+
+```graphql title="schema.graphql"
+type Fruit {
+  name: String!
+  price: Decimal!
+}
+
+type FruitOrder {
+  name: Ordering
+  price: Ordering
+}
+
+type PaginationInfo {
+  limit: Int!
+  offset: Int!
+}
+
+type FruitOffsetPaginated {
+  pageInfo: PaginationInfo!
+  totalCount: Int!
+  results: [Fruit]!
+}
+
+input OffsetPaginationInput {
+  offset: Int! = 0
+  limit: Int = null
+}
+
+type Query {
+  fruits(
+    onlyAvailable: Boolean! = true
+    pagination: OffsetPaginationInput
+    order: FruitOrder
+  ): [FruitOffsetPaginated!]!
+}
+```
+
+### Customizing the pagination
+
+Like other generics, `OffsetPaginated` can be customized to modify its behavior or to
+add extra functionality in it. For example, suppose we want to add the average
+price of the fruits in the pagination:
+
+```python title="types.py"
+from strawberry_django.pagination import OffsetPaginated
+
+
+@strawberry_django.type(models.Fruit)
+class Fruit:
+    name: auto
+    price: auto
+
+
+@strawberry.type
+class FruitOffsetPaginated(OffsetPaginated[Fruit]):
+    @strawberry_django.field
+    def average_price(self) -> Decimal:
+        if self.queryset is None:
+            return Decimal(0)
+
+        return self.queryset.aggregate(Avg("price"))["price__avg"]
+
+    @strawberry_django.field
+    def paginated_average_price(self) -> Decimal:
+        paginated_queryset = self.get_paginated_queryset()
+        if paginated_queryset is None:
+            return Decimal(0)
+
+        return paginated_queryset.aggregate(Avg("price"))["price__avg"]
+
+
+@strawberry.type
+class Query:
+    fruits: FruitOffsetPaginated = strawberry_django.offset_paginated()
+```
+
+Would produce the following schema:
+
+```graphql title="schema.graphql"
+type Fruit {
+  name: String!
+}
+
+type PaginationInfo {
+  limit: Int = null
+  offset: Int!
+}
+
+type FruitOffsetPaginated {
+  pageInfo: PaginationInfo!
+  totalCount: Int!
+  results: [Fruit]!
+  averagePrice: Decimal!
+  paginatedAveragePrice: Decimal!
+}
+
+input OffsetPaginationInput {
+  offset: Int! = 0
+  limit: Int = null
+}
+
+type Query {
+  fruits(pagination: OffsetPaginationInput): [FruitOffsetPaginated!]!
+}
+```
+
+The following attributes/methods can be accessed in the `OffsetPaginated` class:
+
+- `queryset`: The queryset original queryset with any filters/ordering applied,
+  but not paginated yet
+- `pagination`: The `OffsetPaginationInput` object, with the `offset` and `limit` for pagination
+- `get_total_count()`: Returns the total count of elements in the queryset without pagination
+- `get_paginated_queryset()`: Returns the queryset with pagination applied
+- `resolve_paginated(queryset, *, info, pagiantion, **kwargs)`: The classmethod that
+  strawberry-django calls to create an instance of the `OffsetPaginated` class/subclass.
 
-## Relay pagination
+## Cursor pagination (aka Relay style pagination)
 
-For more complex scenarios, a cursor pagination would be better. For this,
-use the [relay integration](./relay.md) to define those.
+Another option for pagination is to use a
+[relay style cursor pagination](https://graphql.org/learn/pagination). For this,
+you can leverage the [relay integration](./relay.md) provided by strawberry
+to create a relay connection.

docs/guide/settings.md

@@ -62,7 +62,11 @@ A dictionary with the following optional keys:
 
       If True, [legacy filters](filters.md#legacy-filtering) are enabled. This is usefull for migrating from previous version.
 
-These features can be enabled by adding this code to your `settings.py` file.
+- **`PAGINATION_DEFAULT_LIMIT`** (default: `100`)
+
+      Defualt limit for [pagination](pagination.md) when one is not provided by the client. Can be set to `None` to set it to unlimited.
+
+These features can be enabled by adding this code to your `settings.py` file, like:
 
 ```python title="settings.py"
 STRAWBERRY_DJANGO = {
@@ -73,5 +77,6 @@ STRAWBERRY_DJANGO = {
     "GENERATE_ENUMS_FROM_CHOICES": False,
     "MAP_AUTO_ID_AS_GLOBAL_ID": True,
     "DEFAULT_PK_FIELD_NAME": "id",
+    "PAGINATION_DEFAULT_LIMIT": 250,
 }
 ```

strawberry_django/__init__.py

@@ -1,5 +1,5 @@
 from . import auth, filters, mutations, ordering, pagination, relay
-from .fields.field import connection, field, node
+from .fields.field import connection, field, node, offset_paginated
 from .fields.filter_order import filter_field, order_field
 from .fields.filter_types import (
     BaseFilterLookup,
@@ -60,6 +60,7 @@
     "mutation",
     "mutations",
     "node",
+    "offset_paginated",
     "order",
     "order_field",
     "ordering",

strawberry_django/fields/base.py

@@ -85,14 +85,18 @@ def is_async(self) -> bool:
 
     @functools.cached_property
     def django_type(self) -> type[WithStrawberryDjangoObjectDefinition] | None:
+        from strawberry_django.pagination import OffsetPaginated
+
         origin = self.type
 
         if isinstance(origin, LazyType):
             origin = origin.resolve_type()
 
         object_definition = get_object_definition(origin)
 
-        if object_definition and issubclass(object_definition.origin, relay.Connection):
+        if object_definition and issubclass(
+            object_definition.origin, (relay.Connection, OffsetPaginated)
+        ):
             origin_specialized_type_var_map = (
                 get_specialized_type_var_map(cast(type, origin)) or {}
             )
@@ -148,6 +152,16 @@ def is_list(self) -> bool:
 
         return isinstance(type_, StrawberryList)
 
+    @functools.cached_property
+    def is_paginated(self) -> bool:
+        from strawberry_django.pagination import OffsetPaginated
+
+        type_ = self.type
+        if isinstance(type_, StrawberryOptional):
+            type_ = type_.of_type
+
+        return isinstance(type_, type) and issubclass(type_, OffsetPaginated)
+
     @functools.cached_property
     def is_connection(self) -> bool:
         type_ = self.type