MM-37372 Do not autofollow threads started by webhooks/bots for user who created them (#18276)

* Do not autofollow threads started by webhooks/bots for user who created them

* Add test

app/notification.go

@@ -201,9 +201,11 @@ func (a *App) SendNotifications(post *model.Post, team *model.Team, channel *mod
 	if *a.Config().ServiceSettings.ThreadAutoFollow && post.RootId != "" {
 		var rootMentions *ExplicitMentions
 		if parentPostList != nil {
-			threadParticipants[parentPostList.Posts[parentPostList.Order[0]].UserId] = true
+			rootPost := parentPostList.Posts[parentPostList.Order[0]]
+			if rootPost.GetProp("from_webhook") != "true" {
+				threadParticipants[rootPost.UserId] = true
+			}
 			if channel.Type != model.ChannelTypeDirect {
-				rootPost := parentPostList.Posts[parentPostList.Order[0]]
 				rootMentions = getExplicitMentions(rootPost, keywords, groups)
 				for id := range rootMentions.Mentions {
 					threadParticipants[id] = true

app/notification_test.go

@@ -2705,4 +2705,47 @@ func TestReplyPostNotificationsWithCRT(t *testing.T) {
 		// Then: last post is still marked as unread
 		require.Equal(t, int64(1), thread.UnreadReplies)
 	})
+
+	t.Run("Replies to post created by webhook should not auto-follow webhook creator", func(t *testing.T) {
+		th := Setup(t).InitBasic()
+		defer th.TearDown()
+
+		th.App.UpdateConfig(func(cfg *model.Config) {
+			*cfg.ServiceSettings.ThreadAutoFollow = true
+			*cfg.ServiceSettings.CollapsedThreads = model.CollapsedThreadsDefaultOn
+		})
+
+		user := th.BasicUser
+
+		rootPost := &model.Post{
+			UserId:    user.Id,
+			ChannelId: th.BasicChannel.Id,
+			Message:   "a message",
+			Props:     model.StringInterface{"from_webhook": "true", "override_username": "a bot"},
+		}
+
+		rootPost, appErr := th.App.CreatePostMissingChannel(th.Context, rootPost, false)
+		require.Nil(t, appErr)
+
+		childPost := &model.Post{
+			UserId:    th.BasicUser2.Id,
+			ChannelId: th.BasicChannel.Id,
+			RootId:    rootPost.Id,
+			Message:   "a reply",
+		}
+		childPost, appErr = th.App.CreatePostMissingChannel(th.Context, childPost, false)
+		require.Nil(t, appErr)
+
+		postList := model.PostList{
+			Order: []string{rootPost.Id, childPost.Id},
+			Posts: map[string]*model.Post{rootPost.Id: rootPost, childPost.Id: childPost},
+		}
+		mentions, err := th.App.SendNotifications(childPost, th.BasicTeam, th.BasicChannel, th.BasicUser2, &postList, true)
+		require.NoError(t, err)
+		assert.False(t, utils.StringInSlice(user.Id, mentions))
+
+		membership, err := th.App.GetThreadMembershipForUser(user.Id, rootPost.Id)
+		assert.Error(t, err)
+		assert.Nil(t, membership)
+	})
 }