Fix: many to many auth (#748)

* fix: many-to-many relationship with auth directive

* chore: formatting

Author: olliethedev

packages/appsync-modelgen-plugin/src/__tests__/visitors/appsync-visitor.test.ts

@@ -985,6 +985,51 @@ describe('AppSyncModelVisitor', () => {
     });
   });
 
+  describe('manyToMany with @auth directive', () => {
+    it('should correctly process @auth directive in manyToMany relation', () => {
+      const schema = /* GraphQL */ `
+        type Post @model @auth(rules: [
+          { allow: groups, groups: ["Admins"] },
+          { allow: public, operations: [read] },
+          { allow: private, operations: [create] }
+        ]){
+          slug: ID! @primaryKey
+          title: String!
+          content: String!
+          tags: [Tag] @manyToMany(relationName: "PostTag")
+        }
+  
+        type Tag @model @auth(rules: [
+          { allow: groups, groups: ["Admins"] },
+          { allow: public, operations: [read] },
+          { allow: private, operations: [create] }
+        ]){
+          name: ID! @primaryKey
+          posts: [Post] @manyToMany(relationName: "PostTag")
+        }
+      `;
+  
+      const { models } = createAndGenerateVisitor(schema, { usePipelinedTransformer: true, respectPrimaryKeyAttributesOnConnectionField: true, transformerVersion: 2 });
+  
+      const jointTableModel = models.PostTag;
+      const authDirective = jointTableModel.directives.find(d => d.name === 'auth');
+  
+      expect(authDirective).toBeDefined();
+      expect(authDirective!.arguments.rules).toEqual([
+        { 
+          allow: 'groups', 
+          groups: ['Admins'], 
+          operations: ['create', 'update', 'delete', 'read'],
+          groupClaim: 'cognito:groups',
+          groupField: undefined,
+          provider: 'userPools',
+        },
+        { allow: 'public', operations: ['read'] },
+        { allow: 'private', operations: ['create'] },
+      ]);
+    });
+  });
+
   describe('Primary Key Type', () => {
     describe('V1 GraphQL schema tests', () => {
       const schemaV1 = /* GraphQL */ `

packages/appsync-modelgen-plugin/src/visitors/appsync-visitor.ts

@@ -965,6 +965,20 @@ export class AppSyncModelVisitor<
         value[1].model,
         graphqlName(toUpper(value[0].directive.arguments.relationName)),
       );
+
+      const extractedAuthDirectives = [...value[0].model.directives, ...value[1].model.directives]
+        .filter(directive => directive.name === 'auth');
+
+      const serializedDirectives = extractedAuthDirectives.map(directive => JSON.stringify(directive));
+
+      const uniqueSerializedDirectives = serializedDirectives.filter((serializedDirective, index, array) =>
+        array.indexOf(serializedDirective) === index
+      );
+
+      const authDirectives = uniqueSerializedDirectives.map(serializedDirective => JSON.parse(serializedDirective));
+
+      intermediateModel.directives = [...intermediateModel.directives, ...authDirectives];
+
       const modelDirective = intermediateModel.directives.find(directive => directive.name === 'model');
       if (modelDirective) {
         // Maps @primaryKey and @index of intermediate model to old @key