From 2417cadcea5afa6a3d1974c0e898d1b3ec8adec6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Rafa=C5=82=20Pito=C5=84?= <rafal@mirumee.com>
Date: Thu, 8 Feb 2024 16:29:17 +0100
Subject: [PATCH] Handle unset variables in schema proxy

---
 CHANGELOG.md                          |  1 +
 ariadne_graphql_proxy/proxy_schema.py | 10 ++++---
 tests/test_proxy_schema.py            | 38 +++++++++++++++++++++++++++
 3 files changed, 46 insertions(+), 3 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 81f6413..3492531 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,6 +3,7 @@
 ## UNRELEASED
 
 - Added `CacheSerializer`, `NoopCacheSerializer` and `JSONCacheSerializer`. Changed `CacheBackend`, `InMemoryCache`, `CloudflareCacheBackend` and `DynamoDBCacheBackend` to accept `serializer` initialization option.
+- Fixed schema proxy returning an error when variable defined in an operation is missing from its variables.
 
 
 ## 0.2.0 (2023-09-25)
diff --git a/ariadne_graphql_proxy/proxy_schema.py b/ariadne_graphql_proxy/proxy_schema.py
index 3560253..7856162 100644
--- a/ariadne_graphql_proxy/proxy_schema.py
+++ b/ariadne_graphql_proxy/proxy_schema.py
@@ -235,9 +235,13 @@ async def root_resolver(
                         "operationName": operation_name,
                         "query": print_ast(query_document),
                         "variables": (
-                            variables
-                            if not variables
-                            else {key: variables[key] for key in query_variables}
+                            {
+                                key: variables[key]
+                                for key in query_variables
+                                if key in variables
+                            }
+                            if variables
+                            else None
                         ),
                     },
                 )
diff --git a/tests/test_proxy_schema.py b/tests/test_proxy_schema.py
index 69226fe..b3fa647 100644
--- a/tests/test_proxy_schema.py
+++ b/tests/test_proxy_schema.py
@@ -771,6 +771,44 @@ async def test_proxy_schema_splits_variables_from_fragments_between_schemas(
     }
 
 
+@pytest.mark.asyncio
+async def test_proxy_schema_handles_omitted_optional_variables(
+    httpx_mock,
+    schema_json,
+):
+    httpx_mock.add_response(url="http://graphql.example.com/", json=schema_json)
+
+    proxy_schema = ProxySchema()
+    proxy_schema.add_remote_schema("http://graphql.example.com/")
+    proxy_schema.get_final_schema()
+
+    await proxy_schema.root_resolver(
+        {},
+        "TestQuery",
+        {"arg": "test"},
+        parse(
+            """
+            query TestQuery($arg: Generic, $other: Generic) {
+              basic(arg: $arg, other: $other)
+            }
+            """
+        ),
+    )
+
+    request = httpx_mock.get_requests(url="http://graphql.example.com/")[-1]
+    assert json.loads(request.content) == {
+        "operationName": "TestQuery",
+        "variables": {"arg": "test"},
+        "query": dedent(
+            """
+            query TestQuery($arg: Generic, $other: Generic) {
+              basic(arg: $arg, other: $other)
+            }
+            """
+        ).strip(),
+    }
+
+
 def test_insert_field_adds_field_into_local_schemas_with_given_type(
     schema, complex_schema
 ):