From 833382c1884f6ca62b16a1e16862fa78aaf483c2 Mon Sep 17 00:00:00 2001
From: Arda TANRIKULU <ardatanrikulu@gmail.com>
Date: Mon, 7 Nov 2022 12:09:34 +0300
Subject: [PATCH] fix(wrap): optional argument value is not defined with
 MapLeafValues transform

---
 .changeset/twelve-owls-glow.md                  |  5 +++++
 packages/wrap/src/transforms/MapLeafValues.ts   | 12 +++++++-----
 .../wrap/tests/transformMapLeafValues.test.ts   | 17 +++++++++++++++++
 3 files changed, 29 insertions(+), 5 deletions(-)
 create mode 100644 .changeset/twelve-owls-glow.md

diff --git a/.changeset/twelve-owls-glow.md b/.changeset/twelve-owls-glow.md
new file mode 100644
index 00000000000..e8bcf7c4dc3
--- /dev/null
+++ b/.changeset/twelve-owls-glow.md
@@ -0,0 +1,5 @@
+---
+'@graphql-tools/wrap': patch
+---
+
+Fix the bug when an optional argument's value is not provided with MapLeafValues transform
diff --git a/packages/wrap/src/transforms/MapLeafValues.ts b/packages/wrap/src/transforms/MapLeafValues.ts
index 1738c5c09af..dcf487d3bcb 100644
--- a/packages/wrap/src/transforms/MapLeafValues.ts
+++ b/packages/wrap/src/transforms/MapLeafValues.ts
@@ -179,14 +179,16 @@ export default class MapLeafValues<TContext = Record<string, any>>
             return newValue === undefined ? v : newValue;
           });
 
-          if (argValue.kind === Kind.VARIABLE) {
+          if (argValue?.kind === Kind.VARIABLE) {
             variableValues[argValue.name.value] = transformedValue;
           } else {
             const newValueNode = astFromValue(transformedValue, argType);
-            argumentNodeMap[argName] = {
-              ...argumentNode,
-              value: newValueNode!,
-            };
+            if (newValueNode != null) {
+              argumentNodeMap[argName] = {
+                ...argumentNode,
+                value: newValueNode,
+              };
+            }
           }
         }
 
diff --git a/packages/wrap/tests/transformMapLeafValues.test.ts b/packages/wrap/tests/transformMapLeafValues.test.ts
index 3e6d9f61648..3602ac6c218 100644
--- a/packages/wrap/tests/transformMapLeafValues.test.ts
+++ b/packages/wrap/tests/transformMapLeafValues.test.ts
@@ -81,4 +81,21 @@ describe('MapLeafValues', () => {
     expect(result.data['testEnum']).toBe('THREE');
     expect(result.data['testScalar']).toBe(15);
   });
+  test('works if optional argument is not provided', async () => {
+    const query = /* GraphQL */ `
+      query MyQuery {
+        testEnum
+        testScalar
+      }
+    `;
+
+    const result = await execute({
+      schema: transformedSchema,
+      document: parse(query),
+    });
+    if (isIncrementalResult(result)) throw Error('result is incremental');
+    assertSome(result.data);
+    expect(result.data['testEnum']).toBe(null);
+    expect(result.data['testScalar']).toBe(null);
+  });
 });