From 06b186629db0c1461249150004b07950dce169ae Mon Sep 17 00:00:00 2001
From: Christophe Prakash <christophe.prakash@sesolabor.com>
Date: Sun, 13 Nov 2022 19:46:47 -0500
Subject: [PATCH 1/2] fetchBaseQuery | Add jsonReplacer param

---
 packages/toolkit/src/query/fetchBaseQuery.ts | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/packages/toolkit/src/query/fetchBaseQuery.ts b/packages/toolkit/src/query/fetchBaseQuery.ts
index 5207ec5bc3..d3dbfb21af 100644
--- a/packages/toolkit/src/query/fetchBaseQuery.ts
+++ b/packages/toolkit/src/query/fetchBaseQuery.ts
@@ -132,6 +132,11 @@ export type FetchBaseQueryArgs = {
    * Defaults to `application/json`;
    */
   jsonContentType?: string
+
+  /**
+   * Custom replacer function used when calling `JSON.stringify()`;
+   */
+  jsonReplacer?: (this: any, key: string, value: any) => any
 } & RequestInit &
   Pick<FetchArgs, 'responseHandler' | 'validateStatus' | 'timeout'>
 
@@ -178,6 +183,8 @@ export type FetchBaseQueryMeta = { request: Request; response?: Response }
  *
  * @param {string} jsonContentType Used when automatically setting the content-type header for a request with a jsonifiable body that does not have an explicit content-type header. Defaults to `application/json`.
  *
+ * @param {(this: any, key: string, value: any) => any} jsonReplacer Custom replacer function used when calling `JSON.stringify()`.
+ * 
  * @param {number} timeout
  * A number in milliseconds that represents the maximum time a request can take before timing out.
  */
@@ -188,6 +195,7 @@ export function fetchBaseQuery({
   paramsSerializer,
   isJsonContentType = defaultIsJsonContentType,
   jsonContentType = 'application/json',
+  jsonReplacer,
   timeout: defaultTimeout,
   validateStatus: globalValidateStatus,
   ...baseFetchOptions
@@ -247,7 +255,7 @@ export function fetchBaseQuery({
     }
 
     if (isJsonifiable(body) && isJsonContentType(config.headers)) {
-      config.body = JSON.stringify(body)
+      config.body = JSON.stringify(body, jsonReplacer)
     }
 
     if (params) {

From 8c380c262044d5eef2f89a707956c7a066c77c1d Mon Sep 17 00:00:00 2001
From: Christophe Prakash <christophe.prakash@sesolabor.com>
Date: Thu, 1 Dec 2022 14:43:07 -0500
Subject: [PATCH 2/2] Add test

---
 .../src/query/tests/fetchBaseQuery.test.tsx   | 41 +++++++++++++++++++
 1 file changed, 41 insertions(+)

diff --git a/packages/toolkit/src/query/tests/fetchBaseQuery.test.tsx b/packages/toolkit/src/query/tests/fetchBaseQuery.test.tsx
index eab78bd59b..7443aa05c4 100644
--- a/packages/toolkit/src/query/tests/fetchBaseQuery.test.tsx
+++ b/packages/toolkit/src/query/tests/fetchBaseQuery.test.tsx
@@ -431,6 +431,47 @@ describe('fetchBaseQuery', () => {
 
       expect(request.headers['content-type']).toBe('application/vnd.api+json')
     })
+
+    it('supports a custom jsonReplacer', async () => {
+      const body = {
+        items: new Set(["A", "B", "C"])
+      }
+
+      let request: any
+      ;({ data: request } = await baseQuery(
+        {
+          url: '/echo',
+          body,
+          method: 'POST',
+        },
+        commonBaseQueryApi,
+        {}
+      ))
+
+      expect(request.headers['content-type']).toBe('application/json')
+      expect(request.body).toEqual({ items: {} }) // Set is not properly marshalled by default
+
+      // Use jsonReplacer
+      const baseQueryWithReplacer = fetchBaseQuery({
+        baseUrl,
+        fetchFn: fetchFn as any,
+        jsonReplacer: (key, value) => value instanceof Set ? [...value] : value
+      })
+
+      ;({ data: request } = await baseQueryWithReplacer(
+        {
+          url: '/echo',
+          body,
+          method: 'POST',
+        },
+        commonBaseQueryApi,
+        {}
+      ))
+
+      expect(request.headers['content-type']).toBe('application/json')
+      expect(request.body).toEqual({ items: ["A", "B", "C"] }) // Set is marshalled correctly by jsonReplacer
+      
+    })
   })
 
   describe('arg.params', () => {