feat(preview): add experimental support for observing full documents

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

@@ -19,6 +19,7 @@ export function createGlobalListener(client: SanityClient) {
         includePreviousRevision: false,
         includeMutations: false,
         visibility: 'query',
+        effectFormat: 'mendoza',
         tag: 'preview.global',
       },
     )

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

@@ -0,0 +1,89 @@
+import {type MutationEvent, type SanityClient, type WelcomeEvent} from '@sanity/client'
+import {type SanityDocument} from '@sanity/types'
+import {memoize, uniq} from 'lodash'
+import {type RawPatch} from 'mendoza'
+import {EMPTY, finalize, type Observable, of} from 'rxjs'
+import {concatMap, map, scan, shareReplay} from 'rxjs/operators'
+
+import {type ApiConfig} from './types'
+import {applyMutationEventEffects} from './utils/applyMendozaPatch'
+import {debounceCollect} from './utils/debounceCollect'
+
+export function createObserveDocument({
+  mutationChannel,
+  client,
+}: {
+  client: SanityClient
+  mutationChannel: Observable<WelcomeEvent | MutationEvent>
+}) {
+  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 $ids]`, {ids: uniq(ids.flat())}, {tag: 'preview.observe-document'})
+          .pipe(
+            // eslint-disable-next-line max-nested-callbacks
+            map((result) => ids.map(([id]) => result.find((r: {_id: string}) => r._id === id))),
+          )
+      }
+      return debounceCollect(batchFetchDocuments, 100)
+    },
+    (apiConfig) => apiConfig.dataset + apiConfig.projectId,
+  )
+
+  const MEMO: Record<string, Observable<SanityDocument | undefined>> = {}
+
+  function observeDocument(id: string, apiConfig?: ApiConfig) {
+    const _apiConfig = apiConfig || {
+      dataset: client.config().dataset!,
+      projectId: client.config().projectId!,
+    }
+    const fetchDocument = getBatchFetcher(_apiConfig)
+    return mutationChannel.pipe(
+      concatMap((event) => {
+        if (event.type === 'welcome') {
+          return fetchDocument(id).pipe(map((document) => ({type: 'sync' as const, document})))
+        }
+        return event.documentId === id ? of(event) : EMPTY
+      }),
+      scan((current: SanityDocument | undefined, event) => {
+        if (event.type === 'sync') {
+          return event.document
+        }
+        if (event.type === 'mutation') {
+          return applyMutationEvent(current, event)
+        }
+        //@ts-expect-error - this should never happen
+        throw new Error(`Unexpected event type: "${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(id, apiConfig).pipe(
+        finalize(() => delete MEMO[key]),
+        shareReplay({bufferSize: 1, refCount: true}),
+      )
+    }
+    return MEMO[key]
+  }
+}
+
+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?',
+    )
+  }
+  return applyMutationEventEffects(
+    current,
+    event as {effects: {apply: RawPatch}; previousRev: string; resultRev: string},
+  )
+}

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

@@ -1,11 +1,12 @@
 import {type MutationEvent, type SanityClient, type WelcomeEvent} from '@sanity/client'
 import {type PrepareViewOptions, type SanityDocument} from '@sanity/types'
-import {type Observable} from 'rxjs'
+import {combineLatest, type Observable} from 'rxjs'
 import {distinctUntilChanged, filter, 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 {createObservePathsDocumentPair} from './documentPair'
@@ -56,6 +57,19 @@ 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 */
@@ -79,6 +93,7 @@ export function createDocumentPreviewStore({
     map((event) => (event.type === 'welcome' ? {type: 'connected' as const} : event)),
   )
 
+  const observeDocument = createObserveDocument({client, mutationChannel: globalListener})
   const observeFields = createObserveFields({client: versionedClient, invalidationChannel})
   const observePaths = createPathObserver({observeFields})
 
@@ -110,6 +125,9 @@ export function createDocumentPreviewStore({
     observeForPreview,
     observeDocumentTypeFromId,
 
+    unstable_observeDocument: observeDocument,
+    unstable_observeDocuments: (ids: string[]) =>
+      combineLatest(ids.map((id) => observeDocument(id))),
     unstable_observeDocumentPairAvailability: observeDocumentPairAvailability,
     unstable_observePathsDocumentPair: observePathsDocumentPair,
   }

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

@@ -0,0 +1,44 @@
+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
+}
+
+/**
+ *
+ * @param document - The document to apply the patch to
+ * @param patch - The mendoza patch to apply
+ * @param baseRev - The revision of the document that the patch is calculated from. This is used to ensure that the patch is applied to the correct revision of the document
+ */
+export function applyMendozaPatch(
+  document: SanityDocument | undefined,
+  patch: RawPatch,
+  baseRev: string,
+): SanityDocument | undefined {
+  if (baseRev !== document?._rev) {
+    throw new Error(
+      'Invalid document revision. The provided patch is calculated from a different revision than the current document',
+    )
+  }
+  const next = applyPatch(omitRev(document), patch)
+  return next === null ? undefined : next
+}
+
+export function applyMutationEventEffects(
+  document: SanityDocument | undefined,
+  event: {effects: {apply: RawPatch}; previousRev: string; resultRev: string},
+) {
+  if (!event.effects) {
+    throw new Error(
+      'Mutation event is missing effects. Is the listener set up with effectFormat=mendoza?',
+    )
+  }
+  const next = applyMendozaPatch(document, event.effects.apply, event.previousRev)
+  // next will be undefined in case of deletion
+  return next ? {...next, _rev: event.resultRev} : undefined
+}