feat(preview): add unstable_observeDocument + unstable_observeDocumen…

…ts to preview store

packages/sanity/src/core/preview/createGlobalListener.ts

@@ -1,14 +1,14 @@
 import {type MutationEvent, type SanityClient, type WelcomeEvent} from '@sanity/client'
-import {merge, timer} from 'rxjs'
+import {defer, merge, timer} from 'rxjs'
 import {filter, share, shareReplay} from 'rxjs/operators'
 
 /**
  * @internal
  * Creates a listener that will emit 'welcome' for all new subscribers immediately, and thereafter emit at every mutation event
  */
 export function createGlobalListener(client: SanityClient) {
-  const allEvents$ = client
-    .listen(
+  const allEvents$ = defer(() =>
+    client.listen(
       '*[!(_id in path("_.**"))]',
       {},
       {
@@ -19,19 +19,19 @@ export function createGlobalListener(client: SanityClient) {
         effectFormat: 'mendoza',
         tag: 'preview.global',
       },
-    )
-    .pipe(
-      filter(
-        (event): event is WelcomeEvent | MutationEvent =>
-          event.type === 'welcome' || event.type === 'mutation',
-      ),
-      share({resetOnRefCountZero: () => timer(2000)}),
-    )
+    ),
+  ).pipe(
+    filter(
+      (event): event is WelcomeEvent | MutationEvent =>
+        event.type === 'welcome' || event.type === 'mutation',
+    ),
+    share({resetOnRefCountZero: () => timer(2000), resetOnComplete: true}),
+  )
 
   const welcome$ = allEvents$.pipe(
     filter((event) => event.type === 'welcome'),
-    shareReplay(1),
+    shareReplay({refCount: true, bufferSize: 1}),
   )
-  const mutations$ = allEvents$.pipe(filter((event) => event.type === 'mutation'))
+  const mutations$ = allEvents$.pipe(filter((event) => event.type === 'mutation')).pipe(share())
   return merge(welcome$, mutations$)
 }

packages/sanity/src/core/preview/createObserveDocument.ts

@@ -1,8 +1,11 @@
 import {type MutationEvent, type SanityClient, type WelcomeEvent} from '@sanity/client'
-import {uniq} from 'lodash'
-import {EMPTY, type Observable, of} from 'rxjs'
-import {concatMap, map, scan} from 'rxjs/operators'
+import {type SanityDocument} from '@sanity/types'
+import {memoize, uniq} from 'lodash'
+import {EMPTY, finalize, type Observable, of} from 'rxjs'
+import {concatMap, map, scan, shareReplay} from 'rxjs/operators'
 
+import {type ApiConfig} from './types'
+import {applyMendozaPatch} from './utils/applyMendozaPatch'
 import {debounceCollect} from './utils/debounceCollect'
 
 export function createObserveDocument({
@@ -12,30 +15,72 @@ export function createObserveDocument({
   client: SanityClient
   mutationChannel: Observable<WelcomeEvent | MutationEvent>
 }) {
-  function batchFetchDocuments(ids: string[][]) {
-    return client.observable
-      .fetch(`*[_id in $ids]`, {ids: uniq(ids.flat())}, {tag: 'preview.observe-document'})
-      .pipe(map((result) => ids.map((id) => result.find(id))))
-  }
+  const getBatchFetcher = memoize(
+    function getBatchFetcher(apiConfig: {dataset: string; projectId: string}) {
+      const _client = client.withConfig(apiConfig)
+
+      function batchFetchDocuments(ids: [string][]) {
+        return _client.observable
+          .fetch(`*[_id in $ids]`, {ids: uniq(ids.flat())}, {tag: 'preview.observe-document'})
+          .pipe(
+            // eslint-disable-next-line max-nested-callbacks
+            map((result) => ids.map(([id]) => result.find((r: {_id: string}) => r._id === id))),
+          )
+      }
+      return debounceCollect(batchFetchDocuments, 100)
+    },
+    (apiConfig) => apiConfig.dataset + apiConfig.projectId,
+  )
 
-  const fetchDocument = debounceCollect(batchFetchDocuments, 10)
+  const MEMO: Record<string, Observable<SanityDocument | undefined>> = {}
 
-  return function observeDocument(id: string) {
+  function observeDocument(id: string, apiConfig?: ApiConfig) {
+    const _apiConfig = apiConfig || {
+      dataset: client.config().dataset!,
+      projectId: client.config().projectId!,
+    }
+    const fetchDocument = getBatchFetcher(_apiConfig)
     return mutationChannel.pipe(
       concatMap((event) => {
         if (event.type === 'welcome') {
-          return fetchDocument(id).pipe(map((document) => ({type: 'sync', document})))
+          return fetchDocument(id).pipe(map((document) => ({type: 'sync' as const, document})))
         }
         return event.documentId === id ? of(event) : EMPTY
       }),
-      scan((current, event) => {
+      scan((current: SanityDocument | undefined, event) => {
         if (event.type === 'sync') {
           return event.document
         }
         if (event.type === 'mutation') {
-          return current
+          return applyMutationEvent(current, event)
         }
+        //@ts-expect-error - this should never happen
+        throw new Error(`Unexpected event type: "${event.type}"`)
       }, undefined),
     )
   }
+  return function memoizedObserveDocument(id: string, apiConfig?: ApiConfig) {
+    const key = apiConfig ? `${id}-${JSON.stringify(apiConfig)}` : id
+    if (!(key in MEMO)) {
+      MEMO[key] = observeDocument(key, apiConfig).pipe(
+        finalize(() => delete MEMO[key]),
+        shareReplay({bufferSize: 1, refCount: true}),
+      )
+    }
+    return MEMO[id]
+  }
+}
+
+function applyMutationEvent(current: SanityDocument | undefined, event: MutationEvent) {
+  if (event.previousRev !== current?._rev) {
+    console.warn('Document out of sync, skipping mutation')
+    return current
+  }
+  if (!event.effects) {
+    throw new Error(
+      'Mutation event is missing effects. Is the listener set up with effectFormat=mendoza?',
+    )
+  }
+  const next = applyMendozaPatch(current, event.effects.apply)
+  return {...next, _rev: event.resultRev}
 }

packages/sanity/src/core/preview/documentPreviewStore.ts

@@ -1,11 +1,13 @@
 import {type SanityClient} from '@sanity/client'
 import {type PrepareViewOptions, type SanityDocument} from '@sanity/types'
-import {type Observable} from 'rxjs'
+import {pick} from 'lodash'
+import {combineLatest, type Observable} from 'rxjs'
 import {distinctUntilChanged, map} from 'rxjs/operators'
 
 import {isRecord} from '../util'
 import {createPreviewAvailabilityObserver} from './availability'
 import {createGlobalListener} from './createGlobalListener'
+import {createObserveDocument} from './createObserveDocument'
 import {createPathObserver} from './createPathObserver'
 import {createPreviewObserver} from './createPreviewObserver'
 import {create_preview_documentPair} from './documentPair'
@@ -31,6 +33,11 @@ export type ObserveForPreviewFn = (
 ) => Observable<PreparedSnapshot>
 
 /**
+ * The document preview store supports subscribing to content for previewing purposes.
+ * Documents observed by this store will be kept in sync and receive real-time updates from all collaborators,
+ * but has no support for optimistic updates, so any local edits will require a server round-trip before becoming visible,
+ * which means this store is less suitable for real-time editing scenarios.
+ *
  * @hidden
  * @beta */
 export interface DocumentPreviewStore {
@@ -51,28 +58,56 @@ export interface DocumentPreviewStore {
     id: string,
     paths: PreviewPath[],
   ) => Observable<DraftsModelDocument<T>>
+
+  /**
+   * Observe a complete document with the given ID
+   * @hidden
+   * @beta
+   */
+  unstable_observeDocument: (id: string) => Observable<SanityDocument | undefined>
+  /**
+   * Observe a list of complete documents with the given IDs
+   * @hidden
+   * @beta
+   */
+  unstable_observeDocuments: (ids: string[]) => Observable<(SanityDocument | undefined)[]>
 }
 
 /** @internal */
 export interface DocumentPreviewStoreOptions {
   client: SanityClient
 }
 
+/** @internal
+ * Should the preview system fetch partial documents or full documents?
+ * Setting this to false will end up fetching full documents for everything that's currently being previewed in the studio
+ * This comes with an extra memory and initial transfer cost, but gives faster updating previews and less likelyhood of displaying
+ * out-of-date previews as documents will be kept in sync by applying mendosa patches, insted of re-fetching preview queries
+ * */
+const FETCH_PARTIAL_DOCUMENTS = false
+
 /** @internal */
 export function createDocumentPreviewStore({
   client,
 }: DocumentPreviewStoreOptions): DocumentPreviewStore {
   const versionedClient = client.withConfig({apiVersion: '1'})
   const globalListener = createGlobalListener(versionedClient)
-
   const invalidationChannel = globalListener.pipe(
     map((event) => (event.type === 'welcome' ? {type: 'connected' as const} : event)),
   )
 
-  const {observeFields} = createObserveFields({
-    client: versionedClient,
-    invalidationChannel,
-  })
+  const observeDocument = createObserveDocument({client, mutationChannel: globalListener})
+
+  function getObserveFields() {
+    if (FETCH_PARTIAL_DOCUMENTS) {
+      return createObserveFields({client: versionedClient, invalidationChannel})
+    }
+    return function observeFields(id: string, fields: string[], apiConfig?: ApiConfig) {
+      return observeDocument(id, apiConfig).pipe(map((doc) => pick(doc, fields)))
+    }
+  }
+
+  const observeFields = getObserveFields()
 
   const {observePaths} = createPathObserver({observeFields})
 
@@ -94,14 +129,15 @@ export function createDocumentPreviewStore({
   const {observePathsDocumentPair} = create_preview_documentPair(versionedClient, observePaths)
 
   // @todo: explain why the API is like this now, and that it should not be like this in the future!
-  const observeDocument = createObserveDocument({client, mutationChannel: globalListener})
 
   return {
     observePaths,
     observeForPreview,
     observeDocumentTypeFromId,
 
-    // eslint-disable-next-line camelcase
+    unstable_observeDocument: observeDocument,
+    unstable_observeDocuments: (ids: string[]) =>
+      combineLatest(ids.map((id) => observeDocument(id))),
     unstable_observeDocumentPairAvailability: observeDocumentPairAvailability,
     unstable_observePathsDocumentPair: observePathsDocumentPair,
   }

packages/sanity/src/core/preview/observeFields.ts

@@ -187,8 +187,7 @@ export function createObserveFields(options: {
     )
   }
 
-  // API
-  return {observeFields: cachedObserveFields}
+  return cachedObserveFields
 
   function pickFrom(objects: Record<string, any>[], fields: string[]) {
     return [...INCLUDE_FIELDS, ...fields].reduce((result, fieldName) => {

packages/sanity/src/core/preview/utils/applyMendozaPatch.ts

@@ -0,0 +1,18 @@
+import {type SanityDocument} from '@sanity/types'
+import {applyPatch, type RawPatch} from 'mendoza'
+
+function omitRev(document: SanityDocument | undefined) {
+  if (document === undefined) {
+    return undefined
+  }
+  const {_rev, ...doc} = document
+  return doc
+}
+
+export function applyMendozaPatch(
+  document: SanityDocument | undefined,
+  patch: RawPatch,
+): SanityDocument | undefined {
+  const next = applyPatch(omitRev(document), patch)
+  return next === null ? undefined : next
+}