[MM-61462] Fix errcheck issues in server/channels/app/post.go (#29205)

Co-authored-by: Ben Schumacher <ben.schumacher@mattermost.com>

server/.golangci.yml

@@ -119,7 +119,6 @@ issues:
         channels/app/plugin_install.go|\
         channels/app/plugin_signature_test.go|\
         channels/app/plugin_test.go|\
-        channels/app/post.go|\
         channels/app/post_helpers_test.go|\
         channels/app/post_test.go|\
         channels/app/security_update_check.go|\

server/channels/app/post.go

@@ -145,7 +145,9 @@ func (a *App) deduplicateCreatePost(rctx request.CTX, post *model.Post) (foundPo
 	var postID string
 	nErr := a.Srv().seenPendingPostIdsCache.Get(post.PendingPostId, &postID)
 	if nErr == cache.ErrKeyNotFound {
-		a.Srv().seenPendingPostIdsCache.SetWithExpiry(post.PendingPostId, unknownPostId, PendingPostIDsCacheTTL)
+		if appErr := a.Srv().seenPendingPostIdsCache.SetWithExpiry(post.PendingPostId, unknownPostId, PendingPostIDsCacheTTL); appErr != nil {
+			return nil, model.NewAppError("deduplicateCreatePost", "api.post.deduplicate_create_post.cache_error", nil, "", http.StatusInternalServerError).Wrap(appErr)
+		}
 		return nil, nil
 	}
 
@@ -193,11 +195,15 @@ func (a *App) CreatePost(c request.CTX, post *model.Post, channel *model.Channel
 		}
 
 		if err != nil {
-			a.Srv().seenPendingPostIdsCache.Remove(post.PendingPostId)
+			if appErr := a.Srv().seenPendingPostIdsCache.Remove(post.PendingPostId); appErr != nil {
+				err = model.NewAppError("CreatePost", "api.post.deduplicate_create_post.cache_error", nil, "", http.StatusInternalServerError).Wrap(appErr)
+			}
 			return
 		}
 
-		a.Srv().seenPendingPostIdsCache.SetWithExpiry(post.PendingPostId, savedPost.Id, PendingPostIDsCacheTTL)
+		if appErr := a.Srv().seenPendingPostIdsCache.SetWithExpiry(post.PendingPostId, savedPost.Id, PendingPostIDsCacheTTL); appErr != nil {
+			err = model.NewAppError("CreatePost", "api.post.deduplicate_create_post.cache_error", nil, "", http.StatusInternalServerError).Wrap(appErr)
+		}
 	}()
 
 	// Validate recipients counts in case it's not DM
@@ -361,7 +367,9 @@ func (a *App) CreatePost(c request.CTX, post *model.Post, channel *model.Channel
 
 	// Update the mapping from pending post id to the actual post id, for any clients that
 	// might be duplicating requests.
-	a.Srv().seenPendingPostIdsCache.SetWithExpiry(post.PendingPostId, rpost.Id, PendingPostIDsCacheTTL)
+	if appErr := a.Srv().seenPendingPostIdsCache.SetWithExpiry(post.PendingPostId, rpost.Id, PendingPostIDsCacheTTL); appErr != nil {
+		return nil, model.NewAppError("CreatePost", "api.post.deduplicate_create_post.cache_error", nil, "", http.StatusInternalServerError).Wrap(appErr)
+	}
 
 	if a.Metrics() != nil {
 		a.Metrics().IncrementPostCreate()
@@ -1536,7 +1544,9 @@ func (a *App) searchPostsInTeam(teamID string, userID string, paramsList []*mode
 
 	posts.SortByCreateAt()
 
-	a.filterInaccessiblePosts(posts, filterPostOptions{assumeSortedCreatedAt: true})
+	if appErr := a.filterInaccessiblePosts(posts, filterPostOptions{assumeSortedCreatedAt: true}); appErr != nil {
+		return nil, appErr
+	}
 
 	return posts, nil
 }

server/i18n/en.json

@@ -2520,6 +2520,10 @@
     "id": "api.post.create_webhook_post.creating.app_error",
     "translation": "Error creating post."
   },
+  {
+    "id": "api.post.deduplicate_create_post.cache_error",
+    "translation": "Failed to cache post after deduplicating a client repeating the same request."
+  },
   {
     "id": "api.post.deduplicate_create_post.failed_to_get",
     "translation": "Failed to fetch original post after deduplicating a client repeating the same request."