[APP-1398] Fix post shadow/like shadow state when replying (#8866)

* Add optimisticReplyCount to post shadow

* Add special util

* Fix subtle bug in query cache

src/state/cache/post-shadow.ts

@@ -24,6 +24,7 @@ export interface PostShadow {
   isDeleted: boolean
   embed: AppBskyEmbedRecord.View | AppBskyEmbedRecordWithMedia.View | undefined
   pinned: boolean
+  optimisticReplyCount: number | undefined
 }
 
 export const POST_TOMBSTONE = Symbol('PostTombstone')
@@ -34,6 +35,14 @@ const shadows: WeakMap<
   Partial<PostShadow>
 > = new WeakMap()
 
+/**
+ * Use with caution! This function returns the raw shadow data for a post.
+ * Prefer using `usePostShadow`.
+ */
+export function dangerousGetPostShadow(post: AppBskyFeedDefs.PostView) {
+  return shadows.get(post)
+}
+
 export function usePostShadow(
   post: AppBskyFeedDefs.PostView,
 ): Shadow<AppBskyFeedDefs.PostView> | typeof POST_TOMBSTONE {
@@ -95,6 +104,11 @@ function mergeShadow(
     repostCount = Math.max(0, repostCount)
   }
 
+  let replyCount = post.replyCount ?? 0
+  if ('optimisticReplyCount' in shadow) {
+    replyCount = shadow.optimisticReplyCount ?? replyCount
+  }
+
   let embed: typeof post.embed
   if ('embed' in shadow) {
     if (
@@ -112,6 +126,7 @@ function mergeShadow(
     embed: embed || post.embed,
     likeCount: likeCount,
     repostCount: repostCount,
+    replyCount: replyCount,
     viewer: {
       ...(post.viewer || {}),
       like: 'likeUri' in shadow ? shadow.likeUri : post.viewer?.like,