Codegen generic types (#3077)

Co-authored-by: Matt Gilson <mgilson@lat.ai>

RELEASE.md

@@ -0,0 +1,3 @@
+Release type: patch
+
+This fixes a bug where codegen would choke trying to find a field in the schema for a generic type.

strawberry/codegen/query_codegen.py

@@ -678,12 +678,32 @@ def _field_from_selection_set(
     ) -> GraphQLField:
         assert selection.selection_set is not None
 
+        parent_type_name = parent_type.name
+
+        # Check if the parent type is generic.
+        # This seems to be tracked by `strawberry` in the `type_var_map`
+        # If the type is generic, then the strawberry generated schema
+        # naming convention is <GenericType,...><ClassName>
+        # The implementation here assumes that the `type_var_map` is ordered,
+        # but insertion order is maintained in python3.6+ (for CPython) and
+        # guaranteed for all python implementations in python3.7+, so that
+        # should be pretty safe.
+        if parent_type.type_var_map:
+            parent_type_name = (
+                "".join(
+                    c.__name__  # type: ignore[union-attr]
+                    for c in parent_type.type_var_map.values()
+                )
+                + parent_type.name
+            )
+
         selected_field = self.schema.get_field_for_type(
-            selection.name.value, parent_type.name
+            selection.name.value, parent_type_name
         )
+
         assert (
             selected_field
-        ), f"Couldn't find {parent_type.name}.{selection.name.value}"
+        ), f"Couldn't find {parent_type_name}.{selection.name.value}"
 
         selected_field_type, wrapper = self._unwrap_type(selected_field.type)
         name = capitalize_first(to_camel_case(selection.name.value))

tests/codegen/conftest.py

@@ -2,7 +2,7 @@
 import decimal
 import enum
 import random
-from typing import TYPE_CHECKING, List, NewType, Optional, Union
+from typing import TYPE_CHECKING, Generic, List, NewType, Optional, TypeVar, Union
 from typing_extensions import Annotated
 from uuid import UUID
 
@@ -35,6 +35,16 @@ class Animal:
     age: int
 
 
+LivingThing1 = TypeVar("LivingThing1")
+LivingThing2 = TypeVar("LivingThing2")
+
+
+@strawberry.type
+class LifeContainer(Generic[LivingThing1, LivingThing2]):
+    items1: List[LivingThing1]
+    items2: List[LivingThing2]
+
+
 PersonOrAnimal = Annotated[Union[Person, Animal], strawberry.union("PersonOrAnimal")]
 
 
@@ -110,6 +120,13 @@ def get_person_or_animal(self) -> Union[Person, Animal]:
         p_or_a.age = 7
         return p_or_a
 
+    @strawberry.field
+    def list_life() -> LifeContainer[Person, Animal]:
+        """Get lists of living things."""
+        person = Person(name="Henry", age=10)
+        dinosaur = Animal(name="rex", age=66_000_000)
+        return LifeContainer([person], [dinosaur])
+
 
 @strawberry.input
 class BlogPostInput:

tests/codegen/queries/generic_types.graphql

@@ -0,0 +1,12 @@
+query ListLifeGeneric {
+  listLife {
+    items1 {
+      name
+      age
+    }
+    items2 {
+      name
+      age
+    }
+  }
+}

tests/codegen/snapshots/python/generic_types.py

@@ -0,0 +1,16 @@
+from typing import List
+
+class ListLifeGenericResultListLifeItems1:
+    name: str
+    age: int
+
+class ListLifeGenericResultListLifeItems2:
+    name: str
+    age: int
+
+class ListLifeGenericResultListLife:
+    items1: List[ListLifeGenericResultListLifeItems1]
+    items2: List[ListLifeGenericResultListLifeItems2]
+
+class ListLifeGenericResult:
+    list_life: ListLifeGenericResultListLife

tests/codegen/snapshots/typescript/generic_types.ts

@@ -0,0 +1,18 @@
+type ListLifeGenericResultListLifeItems1 = {
+    name: string
+    age: number
+}
+
+type ListLifeGenericResultListLifeItems2 = {
+    name: string
+    age: number
+}
+
+type ListLifeGenericResultListLife = {
+    items1: ListLifeGenericResultListLifeItems1[]
+    items2: ListLifeGenericResultListLifeItems2[]
+}
+
+type ListLifeGenericResult = {
+    list_life: ListLifeGenericResultListLife
+}