feat(relay): Allow to customize max_results per connection in relay (#3746)

Author: bellini666

RELEASE.md

@@ -0,0 +1,27 @@
+Release type: minor
+
+Add the ability to override the "max results" a relay's connection can return on
+a per-field basis.
+
+The default value for this is defined in the schema's config, and set to `100`
+unless modified by the user. Now, that per-field value will take precedence over
+it.
+
+For example:
+
+```python
+@strawerry.type
+class Query:
+    # This will still use the default value in the schema's config
+    fruits: ListConnection[Fruit] = relay.connection()
+
+    # This will reduce the maximum number of results to 10
+    limited_fruits: ListConnection[Fruit] = relay.connection(max_results=10)
+
+    # This will increase the maximum number of results to 10
+    higher_limited_fruits: ListConnection[Fruit] = relay.connection(max_results=10_000)
+```
+
+Note that this only affects `ListConnection` and subclasses. If you are
+implementing your own connection resolver, there's an extra keyword named
+`max_results: int | None` that will be passed to it.

docs/guides/relay.md

@@ -205,9 +205,24 @@ It can be defined in the `Query` objects in 4 ways:
 - `node: List[Optional[Node]]`: The same as `List[Node]`, but the returned list
   can contain `null` values if the given objects don't exist.
 
+### Max results for connections
+
+The implementation of `relay.ListConnection` will limit the number of results to
+the `relay_max_results` configuration in the
+[schema's config](../types/schema-configurations.md) (which defaults to `100`).
+
+That can also be configured on a per-field basis by passing `max_results` to the
+`@connection` decorator. For example:
+
+```python
+@strawerry.type
+class Query:
+    fruits: ListConnection[Fruit] = relay.connection(max_results=10_000)
+```
+
 ### Custom connection pagination
 
-The default `relay.Connection` class don't implement any pagination logic, and
+The default `relay.Connection` class doesn't implement any pagination logic, and
 should be used as a base class to implement your own pagination logic. All you
 need to do is implement the `resolve_connection` classmethod.
 

strawberry/relay/fields.py

@@ -207,6 +207,9 @@ async def resolve(resolved: Any = resolved_nodes) -> list[Node]:
 class ConnectionExtension(FieldExtension):
     connection_type: type[Connection[Node]]
 
+    def __init__(self, max_results: Optional[int] = None) -> None:
+        self.max_results = max_results
+
     def apply(self, field: StrawberryField) -> None:
         field.arguments = [
             *field.arguments,
@@ -313,6 +316,7 @@ def resolve(
             after=after,
             first=first,
             last=last,
+            max_results=self.max_results,
         )
 
     async def resolve_async(
@@ -341,6 +345,7 @@ async def resolve_async(
             after=after,
             first=first,
             last=last,
+            max_results=self.max_results,
         )
 
         # If nodes was an AsyncIterable/AsyncIterator, resolve_connection
@@ -382,6 +387,7 @@ def connection(
     metadata: Optional[Mapping[Any, Any]] = None,
     directives: Optional[Sequence[object]] = (),
     extensions: list[FieldExtension] = (),  # type: ignore
+    max_results: Optional[int] = None,
     # This init parameter is used by pyright to determine whether this field
     # is added in the constructor or not. It is not used to change
     # any behaviour at the moment.
@@ -414,6 +420,9 @@ def connection(
         metadata: The metadata of the field.
         directives: The directives to apply to the field.
         extensions: The extensions to apply to the field.
+        max_results: The maximum number of results this connection can return.
+            Can be set to override the default value of 100 defined in the
+            schema configuration.
         init: Used only for type checking purposes.
 
     Examples:
@@ -476,7 +485,7 @@ def get_some_nodes(self, age: int) -> Iterable[SomeType]: ...
         default_factory=default_factory,
         metadata=metadata,
         directives=directives or (),
-        extensions=[*extensions, ConnectionExtension()],
+        extensions=[*extensions, ConnectionExtension(max_results=max_results)],
     )
     if resolver is not None:
         f = f(resolver)

strawberry/relay/types.py

@@ -717,6 +717,7 @@ def resolve_connection(
         after: Optional[str] = None,
         first: Optional[int] = None,
         last: Optional[int] = None,
+        max_results: Optional[int] = None,
         **kwargs: Any,
     ) -> AwaitableOrValue[Self]:
         """Resolve a connection from nodes.
@@ -731,6 +732,7 @@ def resolve_connection(
             after: Returns the items in the list that come after the specified cursor.
             first: Returns the first n items from the list.
             last: Returns the items in the list that come after the specified cursor.
+            max_results: The maximum number of results to resolve.
             kwargs: Additional arguments passed to the resolver.
 
         Returns:
@@ -767,6 +769,7 @@ def resolve_connection(  # noqa: PLR0915
         after: Optional[str] = None,
         first: Optional[int] = None,
         last: Optional[int] = None,
+        max_results: Optional[int] = None,
         **kwargs: Any,
     ) -> AwaitableOrValue[Self]:
         """Resolve a connection from the list of nodes.
@@ -780,6 +783,7 @@ def resolve_connection(  # noqa: PLR0915
             after: Returns the items in the list that come after the specified cursor.
             first: Returns the first n items from the list.
             last: Returns the items in the list that come after the specified cursor.
+            max_results: The maximum number of results to resolve.
             kwargs: Additional arguments passed to the resolver.
 
         Returns:
@@ -794,6 +798,7 @@ def resolve_connection(  # noqa: PLR0915
             after=after,
             first=first,
             last=last,
+            max_results=max_results,
         )
 
         type_def = get_object_definition(cls)

strawberry/relay/utils.py

@@ -131,11 +131,16 @@ def from_arguments(
         after: str | None = None,
         first: int | None = None,
         last: int | None = None,
+        max_results: int | None = None,
     ) -> Self:
         """Get the slice metadata to use on ListConnection."""
         from strawberry.relay.types import PREFIX
 
-        max_results = info.schema.config.relay_max_results
+        max_results = (
+            max_results
+            if max_results is not None
+            else info.schema.config.relay_max_results
+        )
         start = 0
         end: int | None = None
 

tests/relay/test_connection.py

@@ -8,6 +8,8 @@
 import strawberry
 from strawberry.permission import BasePermission
 from strawberry.relay import Connection, Node
+from strawberry.relay.types import ListConnection
+from strawberry.schema.config import StrawberryConfig
 
 
 @strawberry.type
@@ -34,6 +36,8 @@ def resolve_connection(
         before: Optional[str] = None,
         first: Optional[int] = None,
         last: Optional[int] = None,
+        max_results: Optional[int] = None,
+        **kwargs: Any,
     ) -> Optional[Self]:
         return None
 
@@ -124,3 +128,57 @@ def users(self) -> Optional[list[User]]:  # pragma: no cover
     result = schema.execute_sync(query)
     assert result.data == {"users": None}
     assert result.errors[0].message == "Not allowed"
+
+
+@pytest.mark.parametrize(
+    ("field_max_results", "schema_max_results", "results", "expected"),
+    [
+        (5, 100, 5, 5),
+        (5, 2, 5, 5),
+        (5, 100, 10, 5),
+        (5, 2, 10, 5),
+        (5, 100, 0, 0),
+        (5, 2, 0, 0),
+        (None, 100, 5, 5),
+        (None, 2, 5, 2),
+    ],
+)
+def test_max_results(
+    field_max_results: Optional[int],
+    schema_max_results: int,
+    results: int,
+    expected: int,
+):
+    @strawberry.type
+    class User(Node):
+        id: strawberry.relay.NodeID[str]
+
+    @strawberry.type
+    class Query:
+        @strawberry.relay.connection(
+            ListConnection[User],
+            max_results=field_max_results,
+        )
+        def users(self) -> list[User]:
+            return [User(id=str(i)) for i in range(results)]
+
+    schema = strawberry.Schema(
+        query=Query,
+        config=StrawberryConfig(relay_max_results=schema_max_results),
+    )
+    query = """
+      query {
+        users {
+          edges {
+            node {
+              id
+            }
+          }
+        }
+      }
+    """
+
+    result = schema.execute_sync(query)
+    assert result.data is not None
+    assert isinstance(result.data["users"]["edges"], list)
+    assert len(result.data["users"]["edges"]) == expected