feat: add credentials option for fetch client

Author: Gabrola

.changeset/witty-apricots-exercise.md

@@ -0,0 +1,5 @@
+---
+'@ts-rest/core': minor
+---
+
+Add credentials option for fetch client

apps/docs/docs/core/custom.md

@@ -1,5 +1,10 @@
 # Custom Client
 
+:::info
+The `credentials` option has no effect when using a custom client. Make sure you handle credentials in your custom client
+(e.g., setting `withCredentials` in axios).
+:::
+
 ## Using Axios (custom api override)
 
 By default ts-rest ships with an incredibly simple fetch 
@@ -94,4 +99,4 @@ export class SampleAPI {
 }
 ```
 
-:::
+:::

apps/docs/docs/core/fetch.md

@@ -54,4 +54,18 @@ const data: {
     body: unknown;
 }
 ```
-:::
+:::
+
+
+## Credentials (sending cookies)
+
+The `fetch()` function used by ts-rest does not send cookies in cross-origin requests by default unless the `credentials`
+option is set to `include`.
+
+```typescript
+const client = initClient(contract, {
+  baseUrl: "http://localhost:3333/api",
+  baseHeaders: {},
+  credentials: 'include'
+})
+```

apps/docs/sidebars.js

@@ -39,6 +39,7 @@ const sidebars = {
       items: [
         { type: 'doc', id: 'core/core' },
         { type: 'doc', id: 'core/fetch' },
+        { type: 'doc', id: 'core/custom' },
         { type: 'doc', id: 'core/errors' },
         { type: 'doc', id: 'core/form-data' },
       ],

libs/ts-rest/core/src/lib/client.ts

@@ -74,22 +74,25 @@ export interface ClientArgs {
   baseUrl: string;
   baseHeaders: Record<string, string>;
   api?: ApiFetcher;
+  credentials?: RequestCredentials;
 }
 
 type ApiFetcher = (args: {
   path: string;
   method: string;
   headers: Record<string, string>;
   body: FormData | string | null | undefined;
+  credentials?: RequestCredentials;
 }) => Promise<{ status: number; body: unknown }>;
 
 export const defaultApi: ApiFetcher = async ({
   path,
   method,
   headers,
   body,
+  credentials,
 }) => {
-  const result = await fetch(path, { method, headers, body });
+  const result = await fetch(path, { method, headers, body, credentials });
 
   try {
     return {
@@ -130,6 +133,7 @@ export const fetchApi = (
     return apiFetcher({
       path,
       method: route.method,
+      credentials: clientArgs.credentials,
       headers: {
         ...clientArgs.baseHeaders,
       },
@@ -140,6 +144,7 @@ export const fetchApi = (
   return apiFetcher({
     path,
     method: route.method,
+    credentials: clientArgs.credentials,
     headers: {
       ...clientArgs.baseHeaders,
       'Content-Type': 'application/json',