fix(graphql): generate fields as optional when they contain arguments

Fields with arguments are usually resolved using a separate method with the
@ResolveField() annotation.
Having such field generated as a required property thus proves quite cumbersome
 as it forces assigning a value in the result of parent @query() method.

This makes fields with arguments always optional.

Author: arthurtemple

packages/graphql/lib/graphql-ast.explorer.ts

@@ -314,7 +314,8 @@ export class GraphQLAstExplorer {
     return {
       name: propertyName,
       type: this.addSymbolIfRoot(type),
-      hasQuestionToken: !required,
+      hasQuestionToken:
+        !required || (item as FieldDefinitionNode).arguments?.length > 0,
     };
   }
 

packages/graphql/tests/graphql-ast.explorer.spec.ts

@@ -0,0 +1,33 @@
+import { GraphQLAstExplorer } from '../lib';
+import { gql } from 'graphql-tag';
+
+describe('GraphQLAstExplorer', () => {
+  describe('explore', () => {
+    it('should generate fields as optional when they contain arguments', () => {
+      const astExplorer = new GraphQLAstExplorer();
+
+      const document = gql`
+        type Cat {
+          id: Int!
+          name: String!
+          weight(unit: String!): Int!
+        }
+
+        type Query {
+          cat(id: ID!): Cat
+        }
+      `;
+
+      astExplorer
+        .explore(document, '/dev/null', 'interface', {})
+        .then((sourceFile) => {
+          expect(
+            sourceFile
+              .getStructure()
+              .statements[0].properties.find((prop) => prop.name === 'weight')!
+              .hasQuestionToken,
+          ).toBe(true);
+        });
+    });
+  });
+});