Fix serializeRecord ESLint violations: missing return type and parameter reassignment (#3741)

* Initial plan

* Fix serializeRecord: add return type and avoid parameter reassignment (#3739 Item 1)

Co-authored-by: timovv <1787642+timovv@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: timovv <1787642+timovv@users.noreply.github.com>
Co-authored-by: Timo van Veenendaal <timov@microsoft.com>

Author: Copilot

packages/typespec-test/test/healthInsights_radiologyinsights/generated/typespec-ts/src/static-helpers/serialization/serialize-record.ts

@@ -1,11 +1,15 @@
 // Copyright (c) Microsoft Corporation.
 // Licensed under the MIT License.
 
-export function serializeRecord(item: any, excludes?: string[], serializer?: (item: any) => any) {
-  excludes = excludes ?? [];
+export function serializeRecord(
+  item: any,
+  excludes?: string[],
+  serializer?: (item: any) => any,
+): Record<string, any> {
+  const propertiesToExclude = excludes ?? [];
   const res: any = {};
   for (const key of Object.keys(item)) {
-    if (excludes.includes(key) || item[key] === undefined) {
+    if (propertiesToExclude.includes(key) || item[key] === undefined) {
       continue;
     }
     if (serializer) {

packages/typespec-test/test/openai_generic/generated/typespec-ts/src/static-helpers/serialization/serialize-record.ts

@@ -1,11 +1,15 @@
 // Copyright (c) Microsoft Corporation.
 // Licensed under the MIT License.
 
-export function serializeRecord(item: any, excludes?: string[], serializer?: (item: any) => any) {
-  excludes = excludes ?? [];
+export function serializeRecord(
+  item: any,
+  excludes?: string[],
+  serializer?: (item: any) => any,
+): Record<string, any> {
+  const propertiesToExclude = excludes ?? [];
   const res: any = {};
   for (const key of Object.keys(item)) {
-    if (excludes.includes(key) || item[key] === undefined) {
+    if (propertiesToExclude.includes(key) || item[key] === undefined) {
       continue;
     }
     if (serializer) {

packages/typespec-test/test/openai_non_branded/generated/typespec-ts/src/static-helpers/serialization/serialize-record.ts

@@ -1,10 +1,14 @@
 // Licensed under the MIT License.
 
-export function serializeRecord(item: any, excludes?: string[], serializer?: (item: any) => any) {
-  excludes = excludes ?? [];
+export function serializeRecord(
+  item: any,
+  excludes?: string[],
+  serializer?: (item: any) => any,
+): Record<string, any> {
+  const propertiesToExclude = excludes ?? [];
   const res: any = {};
   for (const key of Object.keys(item)) {
-    if (excludes.includes(key) || item[key] === undefined) {
+    if (propertiesToExclude.includes(key) || item[key] === undefined) {
       continue;
     }
     if (serializer) {

packages/typespec-ts/static/static-helpers/serialization/serialize-record.ts

@@ -2,11 +2,11 @@ export function serializeRecord(
   item: any,
   excludes?: string[],
   serializer?: (item: any) => any
-) {
-  excludes = excludes ?? [];
+): Record<string, any> {
+  const propertiesToExclude = excludes ?? [];
   const res: any = {};
   for (const key of Object.keys(item)) {
-    if (excludes.includes(key) || item[key] === undefined) {
+    if (propertiesToExclude.includes(key) || item[key] === undefined) {
       continue;
     }
     if (serializer) {