From 9d63e37051a20e8dfc583fb9f0781f3b2cad3100 Mon Sep 17 00:00:00 2001
From: Felix Meziere <felix.meziere@gmail.com>
Date: Thu, 16 Sep 2021 12:17:27 +0100
Subject: [PATCH] Allow for hints with same value on multiple different
 resolvers of a given DjangoObjectType.

---
 graphene_django_optimizer/query.py |  2 +-
 tests/schema.py                    | 17 +++++++++++++++++
 tests/test_query.py                | 30 ++++++++++++++++++++++++++++++
 3 files changed, 48 insertions(+), 1 deletion(-)

diff --git a/graphene_django_optimizer/query.py b/graphene_django_optimizer/query.py
index e64f041..8ef4d6a 100644
--- a/graphene_django_optimizer/query.py
+++ b/graphene_django_optimizer/query.py
@@ -269,7 +269,7 @@ def _add_optimization_hints(self, source, target):
         if source:
             if not is_iterable(source):
                 source = (source,)
-            target += source
+            target += [source_item for source_item in source if source_item not in target]
 
     def _get_name_from_resolver(self, resolver):
         optimization_hints = self._get_optimization_hints(resolver)
diff --git a/tests/schema.py b/tests/schema.py
index fc30203..42208df 100644
--- a/tests/schema.py
+++ b/tests/schema.py
@@ -52,6 +52,10 @@ class ItemInterface(graphene.Interface):
         "tests.schema.ItemType",
         name=graphene.String(required=True),
     )
+    aux_filtered_children = graphene.List(
+        "tests.schema.ItemType",
+        name=graphene.String(required=True),
+    )
     children_custom_filtered = gql_optimizer.field(
         ConnectionField("tests.schema.ItemConnection", filter_input=ItemFilterInput()),
         prefetch_related=_prefetch_children,
@@ -82,6 +86,19 @@ def resolve_aux_children_names(root, info):
     def resolve_filtered_children(root, info, name):
         return getattr(root, "gql_filtered_children_" + name)
 
+    @gql_optimizer.resolver_hints(
+        prefetch_related=lambda info, name: Prefetch(
+            "children",
+            queryset=gql_optimizer.query(Item.objects.filter(name=f"some_prefix {name}"), info),
+            # Different queryset than resolve_filtered_children but same to_attr, on purpose
+            # to check equality of Prefetch is based only on to_attr attribute, as it is implemented in Django.
+            to_attr="gql_filtered_children_" + name,
+        ),
+    )
+    def resolve_aux_filtered_children(root, info, name):
+        return getattr(root, "gql_filtered_children_" + name)
+
+
     def resolve_children_custom_filtered(root, info, *_args):
         return getattr(root, "gql_custom_filtered_children")
 
diff --git a/tests/test_query.py b/tests/test_query.py
index fa7339d..2a50b0c 100644
--- a/tests/test_query.py
+++ b/tests/test_query.py
@@ -585,3 +585,33 @@ def test_should_only_use_the_only_and_not_select_related():
     items = gql_optimizer.query(qs, info)
     optimized_items = qs.only("id", "name")
     assert_query_equality(items, optimized_items)
+
+@pytest.mark.django_db
+def test_should_accept_two_hints_with_same_prefetch_to_attr_and_keep_one_of_them():
+    info = create_resolve_info(
+        schema,
+        """
+        query {
+            items(name: "foo") {
+                filteredChildren(name: "bar") {
+                    id
+                    name
+                }
+                auxFilteredChildren(name: "bar") { # Same name to generate Prefetch with same to_attr
+                    id
+                    name
+                }
+            }
+        }
+    """,
+    )
+    qs = Item.objects.filter(name="foo")
+    items = gql_optimizer.query(qs, info)
+    optimized_items = qs.prefetch_related(
+        Prefetch(
+            "children",
+            queryset=Item.objects.filter(name="bar").only('id','name'),
+            to_attr="gql_filtered_children_foo",
+        )
+    )
+    assert_query_equality(items, optimized_items)