MM-14882 Filter out inactive users from out of channel/group mentions (#10685)

* Add FilterByActive to UserSlice type

* Filter out inactive users from out of channel/group mentions

app/notification.go

@@ -126,7 +126,7 @@ func (a *App) SendNotifications(post *model.Post, team *model.Team, channel *mod
 
 		if len(m.OtherPotentialMentions) > 0 && !post.IsSystemMessage() {
 			if result := <-a.Srv.Store.User().GetProfilesByUsernames(m.OtherPotentialMentions, team.Id); result.Err == nil {
-				channelMentions := model.UserSlice(result.Data.([]*model.User))
+				channelMentions := model.UserSlice(result.Data.([]*model.User)).FilterByActive(true)
 
 				var outOfChannelMentions model.UserSlice
 				var outOfGroupsMentions model.UserSlice

model/user.go

@@ -137,6 +137,19 @@ func (u UserSlice) IDs() []string {
 	return ids
 }
 
+func (u UserSlice) FilterByActive(active bool) UserSlice {
+	var matches []*User
+
+	for _, user := range u {
+		if user.DeleteAt == 0 && active {
+			matches = append(matches, user)
+		} else if user.DeleteAt != 0 && !active {
+			matches = append(matches, user)
+		}
+	}
+	return UserSlice(matches)
+}
+
 func (u UserSlice) FilterByID(ids []string) UserSlice {
 	var matches []*User
 	for _, user := range u {

model/user_test.go

@@ -388,3 +388,25 @@ func TestIsValidLocale(t *testing.T) {
 		})
 	}
 }
+
+func TestUserSlice(t *testing.T) {
+	t.Run("FilterByActive", func(t *testing.T) {
+		user0 := &User{Id: "user0", DeleteAt: 0}
+		user1 := &User{Id: "user1", DeleteAt: 0}
+		user2 := &User{Id: "user2", DeleteAt: 1}
+
+		slice := UserSlice([]*User{user0, user1, user2})
+
+		activeUsers := slice.FilterByActive(true)
+		assert.Equal(t, 2, len(activeUsers))
+		for _, user := range activeUsers {
+			assert.True(t, user.DeleteAt == 0)
+		}
+
+		inactiveUsers := slice.FilterByActive(false)
+		assert.Equal(t, 1, len(inactiveUsers))
+		for _, user := range inactiveUsers {
+			assert.True(t, user.DeleteAt != 0)
+		}
+	})
+}