feat(live-preview): expose requestHandler to subscribe.ts (#10947)

### What?
As described in #10946,
allow passing a custom `collectionPopulationRequestHandler` function to
`subscribe`, which passes it along to `handleMessage` and `mergeData`

### Why?
`mergeData` already supports a custom function for this, that
functionality however isn't exposed.
My use case so far was passing along custom Authorization headers.


### How?
Move the functions type defined in `mergeData` to a dedicated
`CollectionPopulationRequestHandler` type, reuse it across `subscribe`,
`handleMessage` and `mergeData`.

---------

Co-authored-by: Jacob Fletcher <jacobsfletch@gmail.com>

Author: janus-reith

packages/live-preview/src/handleMessage.ts

@@ -1,6 +1,6 @@
 import type { FieldSchemaJSON } from 'payload'
 
-import type { LivePreviewMessageEvent } from './types.js'
+import type { CollectionPopulationRequestHandler, LivePreviewMessageEvent } from './types.js'
 
 import { isLivePreviewEvent } from './isLivePreviewEvent.js'
 import { mergeData } from './mergeData.js'
@@ -29,9 +29,10 @@ export const handleMessage = async <T extends Record<string, any>>(args: {
   depth?: number
   event: LivePreviewMessageEvent<T>
   initialData: T
+  requestHandler?: CollectionPopulationRequestHandler
   serverURL: string
 }): Promise<T> => {
-  const { apiRoute, depth, event, initialData, serverURL } = args
+  const { apiRoute, depth, event, initialData, requestHandler, serverURL } = args
 
   if (isLivePreviewEvent(event, serverURL)) {
     const { data, externallyUpdatedRelationship, fieldSchemaJSON, locale } = event.data
@@ -57,6 +58,7 @@ export const handleMessage = async <T extends Record<string, any>>(args: {
       incomingData: data,
       initialData: _payloadLivePreview?.previousData || initialData,
       locale,
+      requestHandler,
       serverURL,
     })
 

packages/live-preview/src/mergeData.ts

@@ -1,6 +1,6 @@
 import type { DocumentEvent, FieldSchemaJSON, PaginatedDocs } from 'payload'
 
-import type { PopulationsByCollection } from './types.js'
+import type { CollectionPopulationRequestHandler, PopulationsByCollection } from './types.js'
 
 import { traverseFields } from './traverseFields.js'
 
@@ -29,21 +29,17 @@ let prevLocale: string | undefined
 
 export const mergeData = async <T extends Record<string, any>>(args: {
   apiRoute?: string
-  collectionPopulationRequestHandler?: ({
-    apiPath,
-    endpoint,
-    serverURL,
-  }: {
-    apiPath: string
-    endpoint: string
-    serverURL: string
-  }) => Promise<Response>
+  /**
+   * @deprecated Use `requestHandler` instead
+   */
+  collectionPopulationRequestHandler?: CollectionPopulationRequestHandler
   depth?: number
   externallyUpdatedRelationship?: DocumentEvent
   fieldSchema: FieldSchemaJSON
   incomingData: Partial<T>
   initialData: T
   locale?: string
+  requestHandler?: CollectionPopulationRequestHandler
   returnNumberOfRequests?: boolean
   serverURL: string
 }): Promise<
@@ -81,7 +77,8 @@ export const mergeData = async <T extends Record<string, any>>(args: {
       let res: PaginatedDocs
 
       const ids = new Set(populations.map(({ id }) => id))
-      const requestHandler = args.collectionPopulationRequestHandler || defaultRequestHandler
+      const requestHandler =
+        args.collectionPopulationRequestHandler || args.requestHandler || defaultRequestHandler
 
       try {
         res = await requestHandler({

packages/live-preview/src/subscribe.ts

@@ -1,20 +1,24 @@
+import type { CollectionPopulationRequestHandler } from './types.js'
+
 import { handleMessage } from './handleMessage.js'
 
 export const subscribe = <T extends Record<string, any>>(args: {
   apiRoute?: string
   callback: (data: T) => void
   depth?: number
   initialData: T
+  requestHandler?: CollectionPopulationRequestHandler
   serverURL: string
 }): ((event: MessageEvent) => Promise<void> | void) => {
-  const { apiRoute, callback, depth, initialData, serverURL } = args
+  const { apiRoute, callback, depth, initialData, requestHandler, serverURL } = args
 
   const onMessage = async (event: MessageEvent) => {
     const mergedData = await handleMessage<T>({
       apiRoute,
       depth,
       event,
       initialData,
+      requestHandler,
       serverURL,
     })
 

packages/live-preview/src/types.ts

@@ -1,5 +1,15 @@
 import type { DocumentEvent, FieldSchemaJSON } from 'payload'
 
+export type CollectionPopulationRequestHandler = ({
+  apiPath,
+  endpoint,
+  serverURL,
+}: {
+  apiPath: string
+  endpoint: string
+  serverURL: string
+}) => Promise<Response>
+
 export type LivePreviewArgs = {}
 
 export type LivePreview = void