fix: null check for custom IAM policies Action array (#12346)

Author: sdstolworthy

packages/amplify-cli-core/src/__tests__/customPoliciesUtils.test.ts

@@ -1,6 +1,6 @@
 import { createDefaultCustomPoliciesFile, generateCustomPoliciesInTemplate } from '../customPoliciesUtils';
 import { printer } from '@aws-amplify/amplify-prompts';
-import { JSONUtilities } from '..';
+import { AmplifyError, JSONUtilities } from '..';
 import { pathManager, PathConstants, stateManager } from '../state-manager';
 import path from 'path';
 import { Template, Fn } from 'cloudform-types';
@@ -136,4 +136,17 @@ describe('Custom policies util test', () => {
 
     expect(template.Resources?.CustomLambdaExecutionPolicy).toBeUndefined();
   });
+  test('test generateCustomPoliciesInTemplate with empty action array', () => {
+    (stateManager.getCustomPolicies as jest.Mock).mockReturnValueOnce([
+      {
+        Action: undefined,
+        Resource: [],
+      },
+    ]);
+    try {
+      generateCustomPoliciesInTemplate({}, 'lambdaResourceName', 'Lambda', 'function');
+    } catch (e) {
+      expect((e as AmplifyError).name).toBe('CustomPoliciesFormatError');
+    }
+  });
 });

packages/amplify-cli-core/src/customPoliciesUtils.ts

@@ -163,7 +163,7 @@ function resourceHasCustomPolicies(customPolicies: CustomIAMPolicies): boolean {
   const customPolicy = _.first(customPolicies);
 
   // if either there are no custom policies in the array or the defined policy is the default
-  if (!customPolicy || (customPolicy && customPolicy.Action.length === 0 && customPolicy.Resource.length == 0)) {
+  if (!customPolicy || (customPolicy && customPolicy.Action?.length === 0 && customPolicy.Resource.length == 0)) {
     return false;
   }