[lib] Avoid creating Promises for showInMessagePreview if not needed

Summary: This solves [ENG-10201](https://linear.app/comm/issue/ENG-10201/cold-start-is-significantly-slower-in-build-460), in a similar way to how D14136 (and associated stack) solved [ENG-9952](https://linear.app/comm/issue/ENG-9952/investigate-performance-regression-on-mobile-build-444). The basic story is that creating too many `Promise`s overwhelms Hermes, and in particular this occurs for many Farcaster-linked communities where all of the recent messages are membership robotext messages about users joining the community. Luckily, we only need `Promise`s for `showInMessagePreview` in `reactionMessageSpec`. This diff simply updates the signature of `showInMessagePreview` to allow for returning immediately (instead of a `Promise`), which solves the performance regression. More context on Linear [here](https://linear.app/comm/issue/ENG-10201/cold-start-is-significantly-slower-in-build-460#comment-8746a762). Test Plan: Deployed a Release build to my iOS device. Prior to this diff, it reproduced the cold start performance regression. Following this diff, it no longer reproduced. Reviewers: tomek, angelika Reviewed By: tomek Differential Revision: https://phab.comm.dev/D14361
CommE2E · Feb 14, 2025 · 520c6e5 · 520c6e5
1 parent 8bc6216
commit 520c6e5
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Showing 7 changed files with 10 additions and 7 deletions.
diff --git a/lib/hooks/message-hooks.js b/lib/hooks/message-hooks.js
@@ -71,10 +71,13 @@ function useGetMessageInfoForPreview(): (
             shouldFetchOlderMessages: false,
           };
         }
-        const shouldShow = await showInMessagePreview(
+        let shouldShow = showInMessagePreview(
           messageInfo,
           showInMessagePreviewParams,
         );
+        if (shouldShow instanceof Promise) {
+          shouldShow = await shouldShow;
+        }
         if (shouldShow) {
           return {
             messageInfoForPreview: messageInfo,

diff --git a/lib/shared/messages/add-members-message-spec.js b/lib/shared/messages/add-members-message-spec.js
@@ -229,7 +229,7 @@ export const addMembersMessageSpec: AddMembersMessageSpec = Object.freeze({
     return { shouldMerge: true, item: mergedItem };
   },
 
-  showInMessagePreview: async (
+  showInMessagePreview: (
     messageInfo: AddMembersMessageInfo,
     params: ShowInMessagePreviewParams,
   ) => threadTypeIsThick(params.threadInfo.type),

diff --git a/lib/shared/messages/join-thread-message-spec.js b/lib/shared/messages/join-thread-message-spec.js
@@ -175,7 +175,7 @@ export const joinThreadMessageSpec: MessageSpec<
     return { shouldMerge: true, item: mergedItem };
   },
 
-  showInMessagePreview: async (
+  showInMessagePreview: (
     messageInfo: JoinThreadMessageInfo,
     params: ShowInMessagePreviewParams,
   ) => threadTypeIsThick(params.threadInfo.type),

diff --git a/lib/shared/messages/leave-thread-message-spec.js b/lib/shared/messages/leave-thread-message-spec.js
@@ -175,7 +175,7 @@ export const leaveThreadMessageSpec: MessageSpec<
     return { shouldMerge: true, item: mergedItem };
   },
 
-  showInMessagePreview: async (
+  showInMessagePreview: (
     messageInfo: LeaveThreadMessageInfo,
     params: ShowInMessagePreviewParams,
   ) => threadTypeIsThick(params.threadInfo.type),

diff --git a/lib/shared/messages/message-spec.js b/lib/shared/messages/message-spec.js
@@ -145,7 +145,7 @@ export type MessageSpec<Data, RawInfo, Info> = {
   +showInMessagePreview?: (
     messageInfo: Info,
     params: ShowInMessagePreviewParams,
-  ) => Promise<boolean>,
+  ) => boolean | Promise<boolean>,
   +getLastUpdatedTime?: (
     messageInfoOrRawMessageInfo: Info | RawInfo,
     params: ShowInMessagePreviewParams,

diff --git a/lib/shared/messages/multimedia-message-spec.js b/lib/shared/messages/multimedia-message-spec.js
@@ -379,7 +379,7 @@ export const multimediaMessageSpec: MultimediaMessageSpec = Object.freeze({
   validator: rawMultimediaMessageInfoValidator,
 
   showInMessagePreview: (messageInfo: MediaMessageInfo | ImagesMessageInfo) =>
-    Promise.resolve(messageInfo.media.length > 0),
+    messageInfo.media.length > 0,
 
   getLastUpdatedTime: (
     messageInfo:

diff --git a/lib/shared/messages/remove-members-message-spec.js b/lib/shared/messages/remove-members-message-spec.js
@@ -235,7 +235,7 @@ export const removeMembersMessageSpec: RemoveMembersMessageSpec = Object.freeze(
       return { shouldMerge: true, item: mergedItem };
     },
 
-    showInMessagePreview: async (
+    showInMessagePreview: (
       messageInfo: RemoveMembersMessageInfo,
       params: ShowInMessagePreviewParams,
     ) => threadTypeIsThick(params.threadInfo.type),