fix: Update S3 client usage in BaseConfigService (#1215)

`BaseConfigService` has been broken since upgrading to AWS SDK v3
(#1201).

- The S3 object body is no longer returned as a `Buffer`, but as a
  `StreamingBlobPayloadOutputTypes`
- Errors now have a capitalised `Code` key, which impacts handling of
  missing config objects

Jira: [ENG-3796]

[ENG-3796]: https://comicrelief.atlassian.net/browse/ENG-3796

Author: seb-cr

src/services/BaseConfigService.ts

@@ -9,7 +9,7 @@ import DependencyAwareClass from '../core/DependencyAwareClass';
 import LambdaTermination from '../utils/LambdaTermination';
 
 /**
- * `error.code` for S3 404 errors.
+ * `error.Code` for S3 404 errors.
  */
 export const S3_NO_SUCH_KEY_ERROR_CODE = 'NoSuchKey';
 
@@ -111,7 +111,7 @@ export default class BaseConfigService extends DependencyAwareClass {
     const response = await this.client.send(new GetObjectCommand(
       (this.constructor as typeof BaseConfigService).s3config,
     ));
-    const body = String(response.Body);
+    const body = await response.Body?.transformToString();
 
     if (!body) {
       // Empty strings are not valid configurations
@@ -135,7 +135,7 @@ export default class BaseConfigService extends DependencyAwareClass {
     try {
       return await this.get();
     } catch (error: any) {
-      if (error.code !== S3_NO_SUCH_KEY_ERROR_CODE) {
+      if (error.Code !== S3_NO_SUCH_KEY_ERROR_CODE) {
         // Throw directly any other error
         throw error;
       }
@@ -157,7 +157,7 @@ export default class BaseConfigService extends DependencyAwareClass {
     try {
       base = await this.get();
     } catch (error: any) {
-      if (error.code !== S3_NO_SUCH_KEY_ERROR_CODE) {
+      if (error.Code !== S3_NO_SUCH_KEY_ERROR_CODE) {
         // Throw directly any other error
         throw error;
       }

tests/unit/services/BaseConfigService.spec.ts

@@ -17,7 +17,7 @@ import {
   DependencyInjection,
 } from '@/src';
 
-type ErrorWithCode = Error & { code?: any };
+type ErrorWithCode = Error & { Code?: any };
 
 /**
  * Generate a BaseConfigService with mock S3 client.
@@ -42,6 +42,12 @@ const getService = (
       let result;
       if (command instanceof GetObjectCommand) {
         result = getObject;
+        const { Body: body } = result;
+        if (typeof body === 'string') {
+          result.Body = {
+            transformToString: () => Promise.resolve(body),
+          };
+        }
       } else if (command instanceof PutObjectCommand) {
         result = putObject;
       } else if (command instanceof DeleteObjectCommand) {
@@ -150,7 +156,7 @@ describe('unit.services.BaseConfigService', () => {
 
     it('propagates the 404', async () => {
       const error: ErrorWithCode = new Error('404');
-      error.code = S3_NO_SUCH_KEY_ERROR_CODE;
+      error.Code = S3_NO_SUCH_KEY_ERROR_CODE;
 
       const service = getService({ getObject: error });
 
@@ -161,7 +167,7 @@ describe('unit.services.BaseConfigService', () => {
   describe('getOrCreate', () => {
     it('uploads the defaultConfig with a 404 error', async () => {
       const error: ErrorWithCode = new Error('404');
-      error.code = S3_NO_SUCH_KEY_ERROR_CODE;
+      error.Code = S3_NO_SUCH_KEY_ERROR_CODE;
 
       const service = getService({ getObject: error });
       const config = await service.getOrCreate();
@@ -171,7 +177,7 @@ describe('unit.services.BaseConfigService', () => {
 
     it('throws any non-404 error', async () => {
       const error: ErrorWithCode = new Error('Bad error');
-      error.code = 'another';
+      error.Code = 'another';
 
       const service = getService({ getObject: error });
 
@@ -193,7 +199,7 @@ describe('unit.services.BaseConfigService', () => {
 
     it('uses the base config if no existing config is found', async () => {
       const error: ErrorWithCode = new Error('404');
-      error.code = S3_NO_SUCH_KEY_ERROR_CODE;
+      error.Code = S3_NO_SUCH_KEY_ERROR_CODE;
       const service = getService({ getObject: error });
 
       const existing = service.constructor.defaultConfig;
@@ -206,7 +212,7 @@ describe('unit.services.BaseConfigService', () => {
 
     it('throws any non-404 error', async () => {
       const error: ErrorWithCode = new Error('Bad error');
-      error.code = 'another';
+      error.Code = 'another';
 
       const service = getService({ getObject: error });