FPAD-7660: Add eslint rule to restrict top level arrow functions

Author: edlouth

eslint.config.mjs

@@ -32,6 +32,14 @@ export default defineConfig(
       '@typescript-eslint/switch-exhaustiveness-check': ['error'],
       'arrow-body-style': ['error', 'as-needed'],
       'keyword-spacing': ['error', { after: true }],
+      'no-restricted-syntax': [
+        'error',
+        {
+          selector: 'ExportNamedDeclaration > VariableDeclaration > VariableDeclarator > ArrowFunctionExpression',
+          message:
+            "Top-level exported functions should use the 'function' keyword for better readability and hoisting.",
+        },
+      ],
       'space-before-blocks': ['error', 'always'],
       'space-before-function-paren': ['error', { anonymous: 'always', named: 'never', asyncArrow: 'always' }],
       'object-curly-spacing': ['error', 'always'],

src/commons/build-partial-update-state-command.ts

@@ -18,14 +18,14 @@ type DeepRequiredKey<T, K extends keyof T> = Omit<T, K> & {
  * @param interventionName - optional intervention name if the event was a fraud intervention
  * @param historyList - list of history items
  */
-export const buildPartialUpdateAccountStateCommand = (
+export function buildPartialUpdateAccountStateCommand(
   finalState: StateDetails,
   eventName: EventsEnum,
   currentTimestamp: number,
   interventionEvent: TxMAIngressEvent,
   historyList: string[],
   interventionName?: AISInterventionTypes,
-): Partial<UpdateItemCommandInput> => {
+): Partial<UpdateItemCommandInput> {
   const eventTimestamp = interventionEvent.event_timestamp_ms ?? interventionEvent.timestamp * 1000;
 
   const baseUpdateItemCommandInput: DeepRequiredKey<
@@ -96,7 +96,7 @@ export const buildPartialUpdateAccountStateCommand = (
   baseUpdateItemCommandInput.UpdateExpression += buildRemoveExpression(finalState);
 
   return baseUpdateItemCommandInput;
-};
+}
 
 /**
  * Helper function to build the Remove Expression for DynamoDB update

src/handlers/account-deletion-processor-handler.ts

@@ -15,7 +15,7 @@ const ddbService = new DynamoDatabaseService(appConfig.tableName);
  * @param context -  This object provides methods and properties that provide information about the invocation, function, and execution environment.
  * @returns - Void. Sends off response to DynamoDB.
  */
-export const handler = async (event: SQSEvent, context: Context): Promise<void> => {
+export async function handler(event: SQSEvent, context: Context): Promise<void> {
   logger.addContext(context);
   if (!event.Records[0]) {
     logger.error('The event does not contain any records.');
@@ -28,7 +28,7 @@ export const handler = async (event: SQSEvent, context: Context): Promise<void>
   }).filter((prom) => prom !== undefined);
   await Promise.all(updateRecordsByIdPromises);
   metric.publishStoredMetrics();
-};
+}
 
 /**
  * Function to take the User ID from the SQS Record.

src/handlers/interventions-processor-handler.ts

@@ -38,7 +38,7 @@ const accountStateEngine = AccountStateEngine.getInstance();
  * @param context - context object
  * @returns - Promise of SQS Partial Batch Response
  */
-export const handler = async (event: SQSEvent, context: Context): Promise<SQSBatchResponse> => {
+export async function handler(event: SQSEvent, context: Context): Promise<SQSBatchResponse> {
   logger.addContext(context);
 
   if (event.Records.length === 0) {
@@ -64,7 +64,7 @@ export const handler = async (event: SQSEvent, context: Context): Promise<SQSBat
   return {
     batchItemFailures: itemFailures,
   };
-};
+}
 
 /**
  * Main worker function. It receives an SQS record and processes it according to business logic

src/handlers/invoke-private-api.ts

@@ -9,7 +9,7 @@ interface CustomEvent {
   headers?: Record<string, string>;
 }
 
-export const handle = async (event: CustomEvent) => {
+export async function handle(event: CustomEvent) {
   const baseUrl = event.baseUrl ?? getBaseUrl();
   const endpoint = event.endpoint ?? getEndpoint();
   const userId = encodeURI(event.userId ?? getUserId());
@@ -34,7 +34,7 @@ export const handle = async (event: CustomEvent) => {
     statusCode: response.status,
     body: JSON.stringify(response),
   };
-};
+}
 
 function getUserId() {
   return getEnvOrThrow('USER_ID');

src/handlers/status-retriever-handler.ts

@@ -17,7 +17,7 @@ const dynamoDatabaseServiceInstance = new DynamoDatabaseService(appConfig.tableN
  * @param context - This object provides methods and properties that provide information about the invocation, function, and execution environment.
  * @returns - The status of the account when matched with the User ID. Returns a default object if unable to do so. Also returns the relevant status code.
  */
-export const handle = async (event: APIGatewayEvent, context: Context): Promise<APIGatewayProxyResult> => {
+export async function handle(event: APIGatewayEvent, context: Context): Promise<APIGatewayProxyResult> {
   logger.addContext(context);
 
   if (!event.pathParameters?.['userId']) {
@@ -71,7 +71,7 @@ export const handle = async (event: APIGatewayEvent, context: Context): Promise<
     statusCode: 500,
     body: JSON.stringify({ message: 'Internal Server Error.' }),
   };
-};
+}
 
 /**
  * Helper function to remove whitespace from the user id and to validate that the event contains a valid user id

src/handlers/txma-handler.ts

@@ -5,7 +5,7 @@ import { sendBatchSqsMessage } from '../services/send-sqs-message';
 import { addMetric, metric } from '../commons/metrics';
 import { MetricNames } from '../data-types/constants';
 
-export const handler = async (event: SQSEvent, context: Context): Promise<void> => {
+export async function handler(event: SQSEvent, context: Context): Promise<void> {
   logger.addContext(context);
 
   if (!process.env['ACCOUNT_DELETION_SQS_QUEUE']) {
@@ -58,4 +58,4 @@ export const handler = async (event: SQSEvent, context: Context): Promise<void>
   }
 
   metric.publishStoredMetrics();
-};
+}

src/services/account-states/account-state-engine.ts

@@ -158,6 +158,7 @@ export class AccountStateEngine {
   }
 }
 
+// eslint-disable-next-line no-restricted-syntax
 export const isCode = (value: string): value is Codes => Object.values(Codes).includes(value as Codes);
 
 /**

src/services/send-sqs-message.ts

@@ -9,10 +9,10 @@ import {
 } from '@aws-sdk/client-sqs';
 import logger from '../commons/logger';
 
-export const sendSqsMessage = async (
+export async function sendSqsMessage(
   messageBody: string,
   queueUrl: string | undefined,
-): Promise<SendMessageCommandOutput> => {
+): Promise<SendMessageCommandOutput> {
   if (!process.env['AWS_REGION']) {
     logger.error('AWS_REGION environment variable is not set');
     throw new Error('AWS_REGION environment variable not set');
@@ -24,12 +24,12 @@ export const sendSqsMessage = async (
     MessageBody: messageBody,
   };
   return client.send(new SendMessageCommand(message));
-};
+}
 
-export const sendBatchSqsMessage = async (
+export async function sendBatchSqsMessage(
   messages: SendMessageBatchRequestEntry[],
   queueUrl: string | undefined,
-): Promise<SendMessageBatchCommandOutput> => {
+): Promise<SendMessageBatchCommandOutput> {
   if (!process.env['AWS_REGION']) {
     logger.error('AWS_REGION environment variable is not set');
     throw new Error('AWS_REGION environment variable not set');
@@ -42,4 +42,4 @@ export const sendBatchSqsMessage = async (
   };
   const command = new SendMessageBatchCommand(parameters);
   return client.send(command);
-};
+}