Fix codegen crash on nullable lists of non-scalars (#3653)

Co-authored-by: Jacob Allen <[email protected]>

RELEASE.md

@@ -0,0 +1,3 @@
+Release type: patch
+
+Fixes an issue where the codegen tool would crash when working with a nullable list of types.

strawberry/codegen/query_codegen.py

@@ -645,20 +645,22 @@ def _unwrap_type(
     ) -> Tuple[
         Union[type, StrawberryType], Optional[Callable[[GraphQLType], GraphQLType]]
     ]:
-        wrapper = None
+        wrapper: Optional[Callable[[GraphQLType], GraphQLType]] = None
 
         if isinstance(type_, StrawberryOptional):
-            type_, wrapper = self._unwrap_type(type_.of_type)
+            type_, previous_wrapper = self._unwrap_type(type_.of_type)
             wrapper = (
                 GraphQLOptional
-                if wrapper is None
-                else lambda t: GraphQLOptional(wrapper(t))  # type: ignore[misc]
+                if previous_wrapper is None
+                else lambda t: GraphQLOptional(previous_wrapper(t))  # type: ignore[misc]
             )
 
         elif isinstance(type_, StrawberryList):
-            type_, wrapper = self._unwrap_type(type_.of_type)
+            type_, previous_wrapper = self._unwrap_type(type_.of_type)
             wrapper = (
-                GraphQLList if wrapper is None else lambda t: GraphQLList(wrapper(t))
+                GraphQLList
+                if previous_wrapper is None
+                else lambda t: GraphQLList(previous_wrapper(t))
             )
 
         elif isinstance(type_, LazyType):

tests/codegen/conftest.py

@@ -101,6 +101,7 @@ class Query:
     person: Person
     optional_person: Optional[Person]
     list_of_people: List[Person]
+    optional_list_of_people: Optional[List[Person]]
     enum: Color
     json: JSON
     union: PersonOrAnimal

tests/codegen/queries/nullable_list_of_non_scalars.graphql

@@ -0,0 +1,6 @@
+query OperationName {
+  optionalListOfPeople {
+    name
+    age
+  }
+}

tests/codegen/snapshots/python/nullable_list_of_non_scalars.py

@@ -0,0 +1,8 @@
+from typing import List, Optional
+
+class OperationNameResultOptionalListOfPeople:
+    name: str
+    age: int
+
+class OperationNameResult:
+    optional_list_of_people: Optional[List[OperationNameResultOptionalListOfPeople]]

tests/codegen/snapshots/typescript/nullable_list_of_non_scalars.ts

@@ -0,0 +1,8 @@
+type OperationNameResultOptionalListOfPeople = {
+    name: string
+    age: number
+}
+
+type OperationNameResult = {
+    optional_list_of_people: OperationNameResultOptionalListOfPeople[] | undefined
+}