[MM-23017] Add check for groups to SendNotifications (#14039)

* MM-23017 Check group mentions as part of notification logic

* Add nil groups to existing test cases

* MM-23017 Add tests for insertGroupMention and addGroupMention

* MM-23017 Add tests for getExplicitMentions that have groups

* Add tests for group store GetMemberUsersNotInChannel

* MM-23017 Add tests for AllowGroupMentions

* MM-23017 Fix error message name

* MM-23017 Swap Checks to Name

* MM-23017 Code review fixes

* Rename var and fix allowGroupMentions test

* MM-23017 Use GetMemberUsersInTeam inside of insertGroupMentions

* MM-23017 use group mentions permission

* Actually call GetMemberUsersInTeam

* Remove unnecessary new line

* Uncomment filter allow reference

* MM-23017 Fix group channel notifications

* Update store layer

* MM-23017 Improve test coverage for group channels

* Trigger CI

* Trigger CI

app/notification.go

@@ -36,6 +36,22 @@ func (a *App) SendNotifications(post *model.Post, team *model.Team, channel *mod
 		close(cmnchan)
 	}()
 
+	var gchan chan store.StoreResult
+	if a.allowGroupMentions(post) {
+		gchan = make(chan store.StoreResult, 1)
+		go func() {
+			groups, err := a.Srv().Store.Group().GetGroups(0, 0, model.GroupSearchOpts{FilterAllowReference: true})
+			groupsMap := make(map[string]*model.Group)
+			if err == nil {
+				for _, group := range groups {
+					groupsMap[group.Name] = group
+				}
+			}
+			gchan <- store.StoreResult{Data: groupsMap, Err: err}
+			close(gchan)
+		}()
+	}
+
 	var fchan chan store.StoreResult
 	if len(post.FileIds) != 0 {
 		fchan = make(chan store.StoreResult, 1)
@@ -58,6 +74,15 @@ func (a *App) SendNotifications(post *model.Post, team *model.Team, channel *mod
 	}
 	channelMemberNotifyPropsMap := result.Data.(map[string]model.StringMap)
 
+	groups := make(map[string]*model.Group)
+	if gchan != nil {
+		result = <-gchan
+		if result.Err != nil {
+			return nil, result.Err
+		}
+		groups = result.Data.(map[string]*model.Group)
+	}
+
 	mentions := &ExplicitMentions{}
 	allActivityPushUserIds := []string{}
 
@@ -76,7 +101,7 @@ func (a *App) SendNotifications(post *model.Post, team *model.Team, channel *mod
 		allowChannelMentions := a.allowChannelMentions(post, len(profileMap))
 		keywords := a.getMentionKeywordsInChannel(profileMap, allowChannelMentions, channelMemberNotifyPropsMap)
 
-		mentions = getExplicitMentions(post, keywords)
+		mentions = getExplicitMentions(post, keywords, groups)
 
 		// Add an implicit mention when a user is added to a channel
 		// even if the user has set 'username mentions' to false in account settings.
@@ -87,6 +112,18 @@ func (a *App) SendNotifications(post *model.Post, team *model.Team, channel *mod
 			}
 		}
 
+		// Iterate through all groups that were mentioned and insert group members into the list of mentions or potential mentions
+		for _, group := range mentions.GroupMentions {
+			anyUsersMentionedByGroup, err := a.insertGroupMentions(group, channel, profileMap, mentions)
+			if err != nil {
+				return nil, err
+			}
+
+			if !anyUsersMentionedByGroup {
+				a.sendNoUsersNotifiedByGroupInChannel(sender, post, channel, group)
+			}
+		}
+
 		// get users that have comment thread mentions enabled
 		if len(post.RootId) > 0 && parentPostList != nil {
 			for _, threadPost := range parentPostList.Posts {
@@ -373,6 +410,18 @@ func (a *App) userAllowsEmail(user *model.User, channelMemberNotificationProps m
 	return userAllowsEmails && emailNotificationsAllowedForStatus && user.DeleteAt == 0 && !autoResponderRelated
 }
 
+func (a *App) sendNoUsersNotifiedByGroupInChannel(sender *model.User, post *model.Post, channel *model.Channel, group *model.Group) {
+	T := utils.GetUserTranslations(sender.Locale)
+	ephemeralPost := &model.Post{
+		UserId:    sender.Id,
+		RootId:    post.RootId,
+		ParentId:  post.ParentId,
+		ChannelId: channel.Id,
+		Message:   T("api.post.check_for_out_of_channel_group_users.message.none", model.StringInterface{"GroupDisplayName": group.DisplayName}),
+	}
+	a.SendEphemeralPost(post.UserId, ephemeralPost)
+}
+
 // sendOutOfChannelMentions sends an ephemeral post to the sender of a post if any of the given potential mentions
 // are outside of the post's channel. Returns whether or not an ephemeral post was sent.
 func (a *App) sendOutOfChannelMentions(sender *model.User, post *model.Post, channel *model.Channel, potentialMentions []string) (bool, error) {
@@ -520,6 +569,9 @@ type ExplicitMentions struct {
 	// Mentions contains the ID of each user that was mentioned and how they were mentioned.
 	Mentions map[string]MentionType
 
+	// Contains a map of groups that were mentioned
+	GroupMentions map[string]*model.Group
+
 	// OtherPotentialMentions contains a list of strings that looked like mentions, but didn't have
 	// a corresponding keyword.
 	OtherPotentialMentions []string
@@ -556,6 +608,9 @@ const (
 
 	// The post contains an at-mention for the user
 	KeywordMention
+
+	// The post contains a group mention for the user
+	GroupMention
 )
 
 func (m *ExplicitMentions) addMention(userId string, mentionType MentionType) {
@@ -570,6 +625,32 @@ func (m *ExplicitMentions) addMention(userId string, mentionType MentionType) {
 	m.Mentions[userId] = mentionType
 }
 
+func (m *ExplicitMentions) addGroupMention(word string, groups map[string]*model.Group) bool {
+	if strings.HasPrefix(word, "@") {
+		word = word[1:]
+	} else {
+		// Only allow group mentions when mentioned directly with @group-name
+		return false
+	}
+
+	group, groupFound := groups[word]
+	if !groupFound {
+		group = groups[strings.ToLower(word)]
+	}
+
+	if group == nil {
+		return false
+	}
+
+	if m.GroupMentions == nil {
+		m.GroupMentions = make(map[string]*model.Group)
+	}
+
+	m.GroupMentions[group.Name] = group
+
+	return true
+}
+
 func (m *ExplicitMentions) addMentions(userIds []string, mentionType MentionType) {
 	for _, userId := range userIds {
 		m.addMention(userId, mentionType)
@@ -582,7 +663,7 @@ func (m *ExplicitMentions) removeMention(userId string) {
 
 // Given a message and a map mapping mention keywords to the users who use them, returns a map of mentioned
 // users and a slice of potential mention users not in the channel and whether or not @here was mentioned.
-func getExplicitMentions(post *model.Post, keywords map[string][]string) *ExplicitMentions {
+func getExplicitMentions(post *model.Post, keywords map[string][]string, groups map[string]*model.Group) *ExplicitMentions {
 	ret := &ExplicitMentions{}
 
 	buf := ""
@@ -591,7 +672,7 @@ func getExplicitMentions(post *model.Post, keywords map[string][]string) *Explic
 		markdown.Inspect(message, func(node interface{}) bool {
 			text, ok := node.(*markdown.Text)
 			if !ok {
-				ret.processText(buf, keywords)
+				ret.processText(buf, keywords, groups)
 				buf = ""
 				return true
 			}
@@ -599,7 +680,7 @@ func getExplicitMentions(post *model.Post, keywords map[string][]string) *Explic
 			return false
 		})
 	}
-	ret.processText(buf, keywords)
+	ret.processText(buf, keywords, groups)
 
 	return ret
 }
@@ -639,6 +720,19 @@ func (a *App) allowChannelMentions(post *model.Post, numProfiles int) bool {
 	return true
 }
 
+// allowGroupMentions returns whether or not the group mentions are allowed for the given post.
+func (a *App) allowGroupMentions(post *model.Post) bool {
+	if !a.HasPermissionToChannel(post.UserId, post.ChannelId, model.PERMISSION_USE_GROUP_MENTIONS) {
+		return false
+	}
+
+	if post.Type == model.POST_HEADER_CHANGE || post.Type == model.POST_PURPOSE_CHANGE {
+		return false
+	}
+
+	return true
+}
+
 // Given a map of user IDs to profiles, returns a list of mention
 // keywords for all users in the channel.
 func (a *App) getMentionKeywordsInChannel(profiles map[string]*model.User, allowChannelMentions bool, channelMemberNotifyPropsMap map[string]model.StringMap) map[string][]string {
@@ -657,6 +751,49 @@ func (a *App) getMentionKeywordsInChannel(profiles map[string]*model.User, allow
 	return keywords
 }
 
+// insertGroupMentions adds group members in the channel to Mentions, adds group members not in the channel to OtherPotentialMentions
+// returns false if no group members present in the team that the channel belongs to
+func (a *App) insertGroupMentions(group *model.Group, channel *model.Channel, profileMap map[string]*model.User, mentions *ExplicitMentions) (bool, *model.AppError) {
+	var err *model.AppError
+	var groupMembers []*model.User
+	outOfChannelGroupMembers := []*model.User{}
+	isGroupOrDirect := channel.IsGroupOrDirect()
+
+	if isGroupOrDirect {
+		groupMembers, err = a.Srv().Store.Group().GetMemberUsers(group.Id)
+	} else {
+		groupMembers, err = a.Srv().Store.Group().GetMemberUsersInTeam(group.Id, channel.TeamId)
+	}
+
+	if err != nil {
+		return false, err
+	}
+
+	if mentions.Mentions == nil {
+		mentions.Mentions = make(map[string]MentionType)
+	}
+
+	for _, member := range groupMembers {
+		if _, ok := profileMap[member.Id]; ok {
+			mentions.Mentions[member.Id] = GroupMention
+		} else {
+			outOfChannelGroupMembers = append(outOfChannelGroupMembers, member)
+		}
+	}
+
+	potentialGroupMembersMentioned := []string{}
+	for _, user := range outOfChannelGroupMembers {
+		potentialGroupMembersMentioned = append(potentialGroupMembersMentioned, user.Username)
+	}
+	if mentions.OtherPotentialMentions == nil {
+		mentions.OtherPotentialMentions = potentialGroupMembersMentioned
+	} else {
+		mentions.OtherPotentialMentions = append(mentions.OtherPotentialMentions, potentialGroupMembersMentioned...)
+	}
+
+	return isGroupOrDirect || len(groupMembers) > 0, nil
+}
+
 // addMentionKeywordsForUser adds the mention keywords for a given user to the given keyword map. Returns the provided keyword map.
 func addMentionKeywordsForUser(keywords map[string][]string, profile *model.User, channelNotifyProps map[string]string, status *model.Status, allowChannelMentions bool) map[string][]string {
 	userMention := "@" + strings.ToLower(profile.Username)
@@ -742,7 +879,7 @@ func (n *PostNotification) GetSenderName(userNameFormat string, overridesAllowed
 }
 
 // checkForMention checks if there is a mention to a specific user or to the keywords here / channel / all
-func (m *ExplicitMentions) checkForMention(word string, keywords map[string][]string) bool {
+func (m *ExplicitMentions) checkForMention(word string, keywords map[string][]string, groups map[string]*model.Group) bool {
 	var mentionType MentionType
 
 	switch strings.ToLower(word) {
@@ -759,6 +896,8 @@ func (m *ExplicitMentions) checkForMention(word string, keywords map[string][]st
 		mentionType = KeywordMention
 	}
 
+	m.addGroupMention(word, groups)
+
 	if ids, match := keywords[strings.ToLower(word)]; match {
 		m.addMentions(ids, mentionType)
 		return true
@@ -795,7 +934,7 @@ func isKeywordMultibyte(keywords map[string][]string, word string) ([]string, bo
 }
 
 // Processes text to filter mentioned users and other potential mentions
-func (m *ExplicitMentions) processText(text string, keywords map[string][]string) {
+func (m *ExplicitMentions) processText(text string, keywords map[string][]string, groups map[string]*model.Group) {
 	systemMentions := map[string]bool{"@here": true, "@channel": true, "@all": true}
 
 	for _, word := range strings.FieldsFunc(text, func(c rune) bool {
@@ -809,16 +948,17 @@ func (m *ExplicitMentions) processText(text string, keywords map[string][]string
 
 		word = strings.TrimLeft(word, ":.-_")
 
-		if m.checkForMention(word, keywords) {
+		if m.checkForMention(word, keywords, groups) {
 			continue
 		}
 
 		foundWithoutSuffix := false
 		wordWithoutSuffix := word
+
 		for len(wordWithoutSuffix) > 0 && strings.LastIndexAny(wordWithoutSuffix, ".-:_") == (len(wordWithoutSuffix)-1) {
 			wordWithoutSuffix = wordWithoutSuffix[0 : len(wordWithoutSuffix)-1]
 
-			if m.checkForMention(wordWithoutSuffix, keywords) {
+			if m.checkForMention(wordWithoutSuffix, keywords, groups) {
 				foundWithoutSuffix = true
 				break
 			}
@@ -844,7 +984,7 @@ func (m *ExplicitMentions) processText(text string, keywords map[string][]string
 			})
 
 			for _, splitWord := range splitWords {
-				if m.checkForMention(splitWord, keywords) {
+				if m.checkForMention(splitWord, keywords, groups) {
 					continue
 				}
 				if _, ok := systemMentions[splitWord]; !ok && strings.HasPrefix(splitWord, "@") {

app/notification_test.go

@@ -304,6 +304,7 @@ func TestGetExplicitMentions(t *testing.T) {
 		Message     string
 		Attachments []*model.SlackAttachment
 		Keywords    map[string][]string
+		Groups      map[string]*model.Group
 		Expected    *ExplicitMentions
 	}{
 		"Nobody": {
@@ -799,6 +800,54 @@ func TestGetExplicitMentions(t *testing.T) {
 				OtherPotentialMentions: []string{"other-one", "other", "other-two"},
 			},
 		},
+		"No groups": {
+			Message: "@nothing",
+			Groups:  map[string]*model.Group{},
+			Expected: &ExplicitMentions{
+				Mentions:               nil,
+				OtherPotentialMentions: []string{"nothing"},
+			},
+		},
+		"No matching groups": {
+			Message: "@nothing",
+			Groups:  map[string]*model.Group{"engineering": {Name: "engineering"}},
+			Expected: &ExplicitMentions{
+				Mentions:               nil,
+				GroupMentions:          nil,
+				OtherPotentialMentions: []string{"nothing"},
+			},
+		},
+		"matching group with no @": {
+			Message: "engineering",
+			Groups:  map[string]*model.Group{"engineering": {Name: "engineering"}},
+			Expected: &ExplicitMentions{
+				Mentions:               nil,
+				GroupMentions:          nil,
+				OtherPotentialMentions: nil,
+			},
+		},
+		"matching group with preceeding @": {
+			Message: "@engineering",
+			Groups:  map[string]*model.Group{"engineering": {Name: "engineering"}},
+			Expected: &ExplicitMentions{
+				Mentions: nil,
+				GroupMentions: map[string]*model.Group{
+					"engineering": {Name: "engineering"},
+				},
+				OtherPotentialMentions: []string{"engineering"},
+			},
+		},
+		"matching upper case group with preceeding @": {
+			Message: "@Engineering",
+			Groups:  map[string]*model.Group{"engineering": {Name: "engineering"}},
+			Expected: &ExplicitMentions{
+				Mentions: nil,
+				GroupMentions: map[string]*model.Group{
+					"engineering": {Name: "engineering"},
+				},
+				OtherPotentialMentions: []string{"Engineering"},
+			},
+		},
 	} {
 		t.Run(name, func(t *testing.T) {
 			post := &model.Post{
@@ -808,7 +857,7 @@ func TestGetExplicitMentions(t *testing.T) {
 				},
 			}
 
-			m := getExplicitMentions(post, tc.Keywords)
+			m := getExplicitMentions(post, tc.Keywords, tc.Groups)
 
 			assert.EqualValues(t, tc.Expected, m)
 		})
@@ -861,7 +910,7 @@ func TestGetExplicitMentionsAtHere(t *testing.T) {
 		}
 		for message, shouldMention := range cases {
 			post := &model.Post{Message: message}
-			m := getExplicitMentions(post, nil)
+			m := getExplicitMentions(post, nil, nil)
 			require.False(t, m.HereMentioned && !shouldMention, "shouldn't have mentioned @here with \"%v\"")
 			require.False(t, !m.HereMentioned && shouldMention, "should've mentioned @here with \"%v\"")
 		}
@@ -869,7 +918,7 @@ func TestGetExplicitMentionsAtHere(t *testing.T) {
 
 	t.Run("Mention @here and someone", func(t *testing.T) {
 		id := model.NewId()
-		m := getExplicitMentions(&model.Post{Message: "@here @user @potential"}, map[string][]string{"@user": {id}})
+		m := getExplicitMentions(&model.Post{Message: "@here @user @potential"}, map[string][]string{"@user": {id}}, nil)
 		require.True(t, m.HereMentioned, "should've mentioned @here with \"@here @user\"")
 		require.Len(t, m.Mentions, 1)
 		require.Equal(t, KeywordMention, m.Mentions[id], "should've mentioned @user with \"@here @user\"")
@@ -879,11 +928,10 @@ func TestGetExplicitMentionsAtHere(t *testing.T) {
 
 	t.Run("Username ending with period", func(t *testing.T) {
 		id := model.NewId()
-		m := getExplicitMentions(&model.Post{Message: "@potential. test"}, map[string][]string{"@user": {id}})
+		m := getExplicitMentions(&model.Post{Message: "@potential. test"}, map[string][]string{"@user": {id}}, nil)
 		require.Equal(t, len(m.OtherPotentialMentions), 1, "should've potential mentions for @potential")
 		assert.Equal(t, "potential", m.OtherPotentialMentions[0])
 	})
-
 }
 
 func TestAllowChannelMentions(t *testing.T) {
@@ -924,6 +972,41 @@ func TestAllowChannelMentions(t *testing.T) {
 	})
 }
 
+func TestAllowGroupMentions(t *testing.T) {
+	th := Setup(t).InitBasic()
+	defer th.TearDown()
+
+	post := &model.Post{ChannelId: th.BasicChannel.Id, UserId: th.BasicUser.Id}
+
+	t.Run("should return true for a regular post with few channel members", func(t *testing.T) {
+		allowGroupMentions := th.App.allowGroupMentions(post)
+		assert.True(t, allowGroupMentions)
+	})
+
+	t.Run("should return false for a channel header post", func(t *testing.T) {
+		headerChangePost := &model.Post{ChannelId: th.BasicChannel.Id, UserId: th.BasicUser.Id, Type: model.POST_HEADER_CHANGE}
+		allowGroupMentions := th.App.allowGroupMentions(headerChangePost)
+		assert.False(t, allowGroupMentions)
+	})
+
+	t.Run("should return false for a channel purpose post", func(t *testing.T) {
+		purposeChangePost := &model.Post{ChannelId: th.BasicChannel.Id, UserId: th.BasicUser.Id, Type: model.POST_PURPOSE_CHANGE}
+		allowGroupMentions := th.App.allowGroupMentions(purposeChangePost)
+		assert.False(t, allowGroupMentions)
+	})
+
+	t.Run("should return false for a post where the post user does not have USE_GROUP_MENTIONS permission", func(t *testing.T) {
+		defer func() {
+			th.AddPermissionToRole(model.PERMISSION_USE_GROUP_MENTIONS.Id, model.CHANNEL_USER_ROLE_ID)
+			th.AddPermissionToRole(model.PERMISSION_USE_GROUP_MENTIONS.Id, model.CHANNEL_ADMIN_ROLE_ID)
+		}()
+		th.RemovePermissionFromRole(model.PERMISSION_USE_GROUP_MENTIONS.Id, model.CHANNEL_USER_ROLE_ID)
+		th.RemovePermissionFromRole(model.PERMISSION_USE_GROUP_MENTIONS.Id, model.CHANNEL_ADMIN_ROLE_ID)
+		allowGroupMentions := th.App.allowGroupMentions(post)
+		assert.False(t, allowGroupMentions)
+	})
+}
+
 func TestGetMentionKeywords(t *testing.T) {
 	th := Setup(t)
 	defer th.TearDown()
@@ -1669,6 +1752,7 @@ func TestIsKeywordMultibyte(t *testing.T) {
 		Message     string
 		Attachments []*model.SlackAttachment
 		Keywords    map[string][]string
+		Groups      map[string]*model.Group
 		Expected    *ExplicitMentions
 	}{
 		"MultibyteCharacter": {
@@ -1760,10 +1844,7 @@ func TestIsKeywordMultibyte(t *testing.T) {
 				},
 			}
 
-			m := getExplicitMentions(post, tc.Keywords)
-			// if tc.Expected.MentionedUserIds == nil {
-			// 	tc.Expected.MentionedUserIds = make(map[string]bool)
-			// }
+			m := getExplicitMentions(post, tc.Keywords, tc.Groups)
 			assert.EqualValues(t, tc.Expected, m)
 		})
 	}
@@ -1913,23 +1994,71 @@ func TestCheckForMentionUsers(t *testing.T) {
 		t.Run(name, func(t *testing.T) {
 
 			e := &ExplicitMentions{}
-			e.checkForMention(tc.Word, tc.Keywords)
+			e.checkForMention(tc.Word, tc.Keywords, nil)
 
 			assert.EqualValues(t, tc.Expected, e)
 		})
 	}
 }
+
+func TestAddGroupMention(t *testing.T) {
+	for name, tc := range map[string]struct {
+		Word     string
+		Groups   map[string]*model.Group
+		Expected bool
+	}{
+		"No groups": {
+			Word:     "nothing",
+			Groups:   map[string]*model.Group{},
+			Expected: false,
+		},
+		"No matching groups": {
+			Word:     "nothing",
+			Groups:   map[string]*model.Group{"engineering": {Name: "engineering"}, "developers": {Name: "developers"}},
+			Expected: false,
+		},
+		"matching group with no @": {
+			Word:     "engineering",
+			Groups:   map[string]*model.Group{"engineering": {Name: "engineering"}, "developers": {Name: "developers"}},
+			Expected: false,
+		},
+		"matching group with preceeding @": {
+			Word:     "@engineering",
+			Groups:   map[string]*model.Group{"engineering": {Name: "engineering"}, "developers": {Name: "developers"}},
+			Expected: true,
+		},
+		"matching upper case group with preceeding @": {
+			Word:     "@Engineering",
+			Groups:   map[string]*model.Group{"engineering": {Name: "engineering"}, "developers": {Name: "developers"}},
+			Expected: true,
+		},
+	} {
+		t.Run(name, func(t *testing.T) {
+			e := &ExplicitMentions{}
+			groupFound := e.addGroupMention(tc.Word, tc.Groups)
+
+			if groupFound {
+				require.Equal(t, len(e.GroupMentions), 1)
+			}
+
+			require.Equal(t, tc.Expected, groupFound)
+		})
+	}
+}
+
 func TestProcessText(t *testing.T) {
 	id1 := model.NewId()
 
 	for name, tc := range map[string]struct {
 		Text     string
 		Keywords map[string][]string
+		Groups   map[string]*model.Group
 		Expected *ExplicitMentions
 	}{
 		"Mention user in text": {
 			Text:     "hello user @user1",
 			Keywords: map[string][]string{"@user1": {id1}},
+			Groups:   map[string]*model.Group{"engineering": {Name: "engineering"}, "developers": {Name: "developers"}},
 			Expected: &ExplicitMentions{
 				Mentions: map[string]MentionType{
 					id1: KeywordMention,
@@ -1939,6 +2068,7 @@ func TestProcessText(t *testing.T) {
 		"Mention user after ending a sentence with full stop": {
 			Text:     "hello user.@user1",
 			Keywords: map[string][]string{"@user1": {id1}},
+			Groups:   map[string]*model.Group{"engineering": {Name: "engineering"}, "developers": {Name: "developers"}},
 			Expected: &ExplicitMentions{
 				Mentions: map[string]MentionType{
 					id1: KeywordMention,
@@ -1957,6 +2087,7 @@ func TestProcessText(t *testing.T) {
 		"Mention user after colon": {
 			Text:     "hello user:@user1",
 			Keywords: map[string][]string{"@user1": {id1}},
+			Groups:   map[string]*model.Group{"engineering": {Name: "engineering"}, "developers": {Name: "developers"}},
 			Expected: &ExplicitMentions{
 				Mentions: map[string]MentionType{
 					id1: KeywordMention,
@@ -1966,6 +2097,7 @@ func TestProcessText(t *testing.T) {
 		"Mention here after colon": {
 			Text:     "hello all:@here",
 			Keywords: map[string][]string{},
+			Groups:   map[string]*model.Group{"engineering": {Name: "engineering"}, "developers": {Name: "developers"}},
 			Expected: &ExplicitMentions{
 				HereMentioned: true,
 			},
@@ -1973,6 +2105,7 @@ func TestProcessText(t *testing.T) {
 		"Mention all after hyphen": {
 			Text:     "hello all-@all",
 			Keywords: map[string][]string{},
+			Groups:   map[string]*model.Group{"engineering": {Name: "engineering"}, "developers": {Name: "developers"}},
 			Expected: &ExplicitMentions{
 				AllMentioned: true,
 			},
@@ -1980,6 +2113,7 @@ func TestProcessText(t *testing.T) {
 		"Mention channel after full stop": {
 			Text:     "hello channel.@channel",
 			Keywords: map[string][]string{},
+			Groups:   map[string]*model.Group{"engineering": {Name: "engineering"}, "developers": {Name: "developers"}},
 			Expected: &ExplicitMentions{
 				ChannelMentioned: true,
 			},
@@ -1987,6 +2121,7 @@ func TestProcessText(t *testing.T) {
 		"Mention other pontential users or system calls": {
 			Text:     "hello @potentialuser and @otherpotentialuser",
 			Keywords: map[string][]string{},
+			Groups:   map[string]*model.Group{"engineering": {Name: "engineering"}, "developers": {Name: "developers"}},
 			Expected: &ExplicitMentions{
 				OtherPotentialMentions: []string{"potentialuser", "otherpotentialuser"},
 			},
@@ -1994,6 +2129,7 @@ func TestProcessText(t *testing.T) {
 		"Mention a real user and another potential user": {
 			Text:     "@user1, you can use @systembot to get help",
 			Keywords: map[string][]string{"@user1": {id1}},
+			Groups:   map[string]*model.Group{"engineering": {Name: "engineering"}, "developers": {Name: "developers"}},
 			Expected: &ExplicitMentions{
 				Mentions: map[string]MentionType{
 					id1: KeywordMention,
@@ -2001,10 +2137,31 @@ func TestProcessText(t *testing.T) {
 				OtherPotentialMentions: []string{"systembot"},
 			},
 		},
+		"Mention a group": {
+			Text:     "@engineering",
+			Keywords: map[string][]string{"@user1": {id1}},
+			Groups:   map[string]*model.Group{"engineering": {Name: "engineering"}, "developers": {Name: "developers"}},
+			Expected: &ExplicitMentions{
+				GroupMentions:          map[string]*model.Group{"engineering": {Name: "engineering"}},
+				OtherPotentialMentions: []string{"engineering"},
+			},
+		},
+		"Mention a real user and another potential user and a group": {
+			Text:     "@engineering @user1, you can use @systembot to get help from",
+			Keywords: map[string][]string{"@user1": {id1}},
+			Groups:   map[string]*model.Group{"engineering": {Name: "engineering"}, "developers": {Name: "developers"}},
+			Expected: &ExplicitMentions{
+				Mentions: map[string]MentionType{
+					id1: KeywordMention,
+				},
+				GroupMentions:          map[string]*model.Group{"engineering": {Name: "engineering"}},
+				OtherPotentialMentions: []string{"engineering", "systembot"},
+			},
+		},
 	} {
 		t.Run(name, func(t *testing.T) {
 			e := &ExplicitMentions{}
-			e.processText(tc.Text, tc.Keywords)
+			e.processText(tc.Text, tc.Keywords, tc.Groups)
 
 			assert.EqualValues(t, tc.Expected, e)
 		})
@@ -2130,3 +2287,105 @@ func TestUserAllowsEmail(t *testing.T) {
 	})
 
 }
+
+func TestInsertGroupMentions(t *testing.T) {
+	th := Setup(t).InitBasic()
+	defer th.TearDown()
+
+	team := th.BasicTeam
+	channel := th.BasicChannel
+	group := th.CreateGroup()
+	group.DisplayName = "engineering"
+	group.Name = "engineering"
+	group, err := th.App.UpdateGroup(group)
+	require.Nil(t, err)
+
+	groupChannelMember := th.CreateUser()
+	th.LinkUserToTeam(groupChannelMember, team)
+	th.App.AddUserToChannel(groupChannelMember, channel)
+	_, err = th.App.UpsertGroupMember(group.Id, groupChannelMember.Id)
+	require.Nil(t, err)
+
+	nonGroupChannelMember := th.CreateUser()
+	th.LinkUserToTeam(nonGroupChannelMember, team)
+	th.App.AddUserToChannel(nonGroupChannelMember, channel)
+
+	nonChannelGroupMember := th.CreateUser()
+	th.LinkUserToTeam(nonChannelGroupMember, team)
+	_, err = th.App.UpsertGroupMember(group.Id, nonChannelGroupMember.Id)
+	require.Nil(t, err)
+
+	groupWithNoMembers := th.CreateGroup()
+	groupWithNoMembers.DisplayName = "marketing"
+	groupWithNoMembers.Name = "marketing"
+	groupWithNoMembers, err = th.App.UpdateGroup(groupWithNoMembers)
+	require.Nil(t, err)
+
+	profileMap := map[string]*model.User{groupChannelMember.Id: groupChannelMember, nonGroupChannelMember.Id: nonGroupChannelMember}
+
+	t.Run("should add expected mentions for users part of the mentioned group", func(t *testing.T) {
+		mentions := &ExplicitMentions{}
+		usersMentioned, err := th.App.insertGroupMentions(group, channel, profileMap, mentions)
+		require.Nil(t, err)
+		require.Equal(t, usersMentioned, true)
+
+		// Ensure group member that is also a channel member is added to the mentions list.
+		require.Equal(t, len(mentions.Mentions), 1)
+		_, found := mentions.Mentions[groupChannelMember.Id]
+		require.Equal(t, found, true)
+
+		// Ensure group member that is not a channel member is added to the other potential mentions list.
+		require.Equal(t, len(mentions.OtherPotentialMentions), 1)
+		require.Equal(t, mentions.OtherPotentialMentions[0], nonChannelGroupMember.Username)
+	})
+
+	t.Run("should add no expected or potential mentions if the group has no users ", func(t *testing.T) {
+		mentions := &ExplicitMentions{}
+		usersMentioned, err := th.App.insertGroupMentions(groupWithNoMembers, channel, profileMap, mentions)
+		require.Nil(t, err)
+		require.Equal(t, usersMentioned, false)
+
+		// Ensure no mentions are added for a group with no users
+		require.Equal(t, len(mentions.Mentions), 0)
+		require.Equal(t, len(mentions.OtherPotentialMentions), 0)
+	})
+
+	t.Run("should keep existing mentions", func(t *testing.T) {
+		mentions := &ExplicitMentions{}
+		th.App.insertGroupMentions(group, channel, profileMap, mentions)
+		th.App.insertGroupMentions(groupWithNoMembers, channel, profileMap, mentions)
+
+		// Ensure mentions from group are kept after running with groupWithNoMembers
+		require.Equal(t, len(mentions.Mentions), 1)
+		require.Equal(t, len(mentions.OtherPotentialMentions), 1)
+	})
+
+	t.Run("should return true if no members mentioned while in group or direct message channel", func(t *testing.T) {
+		mentions := &ExplicitMentions{}
+		emptyProfileMap := make(map[string]*model.User)
+
+		groupChannel := &model.Channel{Type: model.CHANNEL_GROUP}
+		usersMentioned, _ := th.App.insertGroupMentions(group, groupChannel, emptyProfileMap, mentions)
+		// Ensure group channel with no group members mentioned always returns true
+		require.Equal(t, usersMentioned, true)
+		require.Equal(t, len(mentions.Mentions), 0)
+
+		directChannel := &model.Channel{Type: model.CHANNEL_DIRECT}
+		usersMentioned, _ = th.App.insertGroupMentions(group, directChannel, emptyProfileMap, mentions)
+		// Ensure direct channel with no group members mentioned always returns true
+		require.Equal(t, usersMentioned, true)
+		require.Equal(t, len(mentions.Mentions), 0)
+	})
+
+	t.Run("should add mentions for members while in group channel", func(t *testing.T) {
+		groupChannel, err := th.App.CreateGroupChannel([]string{groupChannelMember.Id, nonGroupChannelMember.Id, th.BasicUser.Id}, groupChannelMember.Id)
+		require.Nil(t, err)
+
+		mentions := &ExplicitMentions{}
+		th.App.insertGroupMentions(group, groupChannel, profileMap, mentions)
+
+		require.Equal(t, len(mentions.Mentions), 1)
+		_, found := mentions.Mentions[groupChannelMember.Id]
+		require.Equal(t, found, true)
+	})
+}

app/post.go

@@ -1230,7 +1230,7 @@ func isPostMention(user *model.User, post *model.Post, keywords map[string][]str
 	}
 
 	// Check for keyword mentions
-	mentions := getExplicitMentions(post, keywords)
+	mentions := getExplicitMentions(post, keywords, make(map[string]*model.Group))
 	if _, ok := mentions.Mentions[user.Id]; ok {
 		return true
 	}

i18n/en.json

@@ -1600,6 +1600,10 @@
     "id": "api.plugin.verify_plugin.app_error",
     "translation": "Unable to verify plugin signature."
   },
+  {
+    "id": "api.post.check_for_out_of_channel_group_users.message.none",
+    "translation": "@{{.GroupDisplayName}} has no members on this team"
+  },
   {
     "id": "api.post.check_for_out_of_channel_groups_mentions.message.multiple",
     "translation": "@{{.Usernames}} and @{{.LastUsername}} did not get notified by this mention because they are not in the channel. They cannot be added to the channel because they are not a member of the linked groups. To add them to this channel, they must be added to the linked groups."

store/opentracing_layer.go

@@ -3337,6 +3337,42 @@ func (s *OpenTracingLayerGroupStore) GetMemberUsers(groupID string) ([]*model.Us
 	return resultVar0, resultVar1
 }
 
+func (s *OpenTracingLayerGroupStore) GetMemberUsersInTeam(groupID string, teamID string) ([]*model.User, *model.AppError) {
+	origCtx := s.Root.Store.Context()
+	span, newCtx := tracing.StartSpanWithParentByContext(s.Root.Store.Context(), "GroupStore.GetMemberUsersInTeam")
+	s.Root.Store.SetContext(newCtx)
+	defer func() {
+		s.Root.Store.SetContext(origCtx)
+	}()
+
+	defer span.Finish()
+	resultVar0, resultVar1 := s.GroupStore.GetMemberUsersInTeam(groupID, teamID)
+	if resultVar1 != nil {
+		span.LogFields(spanlog.Error(resultVar1))
+		ext.Error.Set(span, true)
+	}
+
+	return resultVar0, resultVar1
+}
+
+func (s *OpenTracingLayerGroupStore) GetMemberUsersNotInChannel(groupID string, channelID string) ([]*model.User, *model.AppError) {
+	origCtx := s.Root.Store.Context()
+	span, newCtx := tracing.StartSpanWithParentByContext(s.Root.Store.Context(), "GroupStore.GetMemberUsersNotInChannel")
+	s.Root.Store.SetContext(newCtx)
+	defer func() {
+		s.Root.Store.SetContext(origCtx)
+	}()
+
+	defer span.Finish()
+	resultVar0, resultVar1 := s.GroupStore.GetMemberUsersNotInChannel(groupID, channelID)
+	if resultVar1 != nil {
+		span.LogFields(spanlog.Error(resultVar1))
+		ext.Error.Set(span, true)
+	}
+
+	return resultVar0, resultVar1
+}
+
 func (s *OpenTracingLayerGroupStore) GetMemberUsersPage(groupID string, page int, perPage int) ([]*model.User, *model.AppError) {
 	origCtx := s.Root.Store.Context()
 	span, newCtx := tracing.StartSpanWithParentByContext(s.Root.Store.Context(), "GroupStore.GetMemberUsersPage")

store/sqlstore/group_store.go

@@ -260,7 +260,7 @@ func (s *SqlGroupStore) GetMemberUsers(groupID string) ([]*model.User, *model.Ap
 			AND GroupId = :GroupId`
 
 	if _, err := s.GetReplica().Select(&groupMembers, query, map[string]interface{}{"GroupId": groupID}); err != nil {
-		return nil, model.NewAppError("SqlGroupStore.GroupGetAllBySource", "store.select_error", nil, err.Error(), http.StatusInternalServerError)
+		return nil, model.NewAppError("SqlGroupStore.GetMemberUsers", "store.select_error", nil, err.Error(), http.StatusInternalServerError)
 	}
 
 	return groupMembers, nil
@@ -312,6 +312,70 @@ func (s *SqlGroupStore) GetMemberCount(groupID string) (int64, *model.AppError)
 	return count, nil
 }
 
+func (s *SqlGroupStore) GetMemberUsersInTeam(groupID string, teamID string) ([]*model.User, *model.AppError) {
+	var groupMembers []*model.User
+
+	query := `
+		SELECT
+			Users.*
+		FROM
+			GroupMembers
+			JOIN Users ON Users.Id = GroupMembers.UserId
+		WHERE
+			GroupId = :GroupId
+			AND GroupMembers.UserId IN (
+				SELECT TeamMembers.UserId
+				FROM TeamMembers
+				JOIN Teams ON Teams.Id = :TeamId
+				WHERE TeamMembers.TeamId = Teams.Id
+				AND TeamMembers.DeleteAt = 0
+			)
+			AND GroupMembers.DeleteAt = 0
+			AND Users.DeleteAt = 0
+		`
+
+	if _, err := s.GetReplica().Select(&groupMembers, query, map[string]interface{}{"GroupId": groupID, "TeamId": teamID}); err != nil {
+		return nil, model.NewAppError("SqlGroupStore.GetMemberUsersInTeam", "store.select_error", nil, err.Error(), http.StatusInternalServerError)
+	}
+
+	return groupMembers, nil
+}
+
+func (s *SqlGroupStore) GetMemberUsersNotInChannel(groupID string, channelID string) ([]*model.User, *model.AppError) {
+	var groupMembers []*model.User
+
+	query := `
+		SELECT
+			Users.*
+		FROM
+			GroupMembers
+			JOIN Users ON Users.Id = GroupMembers.UserId
+		WHERE
+			GroupId = :GroupId
+			AND GroupMembers.UserId NOT IN (
+				SELECT ChannelMembers.UserId
+				FROM ChannelMembers
+				WHERE ChannelMembers.ChannelId = :ChannelId
+			)
+			AND GroupMembers.UserId IN (
+				SELECT TeamMembers.UserId
+				FROM TeamMembers
+				JOIN Channels ON Channels.Id = :ChannelId
+				JOIN Teams ON Teams.Id = Channels.TeamId
+				WHERE TeamMembers.TeamId = Teams.Id
+				AND TeamMembers.DeleteAt = 0
+			)
+			AND GroupMembers.DeleteAt = 0
+			AND Users.DeleteAt = 0
+		`
+
+	if _, err := s.GetReplica().Select(&groupMembers, query, map[string]interface{}{"GroupId": groupID, "ChannelId": channelID}); err != nil {
+		return nil, model.NewAppError("SqlGroupStore.GetMemberUsersNotInChannel", "store.select_error", nil, err.Error(), http.StatusInternalServerError)
+	}
+
+	return groupMembers, nil
+}
+
 func (s *SqlGroupStore) UpsertMember(groupID string, userID string) (*model.GroupMember, *model.AppError) {
 	member := &model.GroupMember{
 		GroupId:  groupID,
@@ -1081,10 +1145,14 @@ func (s *SqlGroupStore) GetGroups(page, perPage int, opts model.GroupSearchOpts)
 	groupsQuery = groupsQuery.
 		From("UserGroups g").
 		Where("g.DeleteAt = 0").
-		Limit(uint64(perPage)).
-		Offset(uint64(page * perPage)).
 		OrderBy("g.DisplayName")
 
+	if perPage != 0 {
+		groupsQuery = groupsQuery.
+			Limit(uint64(perPage)).
+			Offset(uint64(page * perPage))
+	}
+
 	if opts.FilterAllowReference {
 		groupsQuery = groupsQuery.Where("g.AllowReference = true")
 	}

store/store.go

@@ -629,6 +629,10 @@ type GroupStore interface {
 	GetMemberUsers(groupID string) ([]*model.User, *model.AppError)
 	GetMemberUsersPage(groupID string, page int, perPage int) ([]*model.User, *model.AppError)
 	GetMemberCount(groupID string) (int64, *model.AppError)
+
+	GetMemberUsersInTeam(groupID string, teamID string) ([]*model.User, *model.AppError)
+	GetMemberUsersNotInChannel(groupID string, channelID string) ([]*model.User, *model.AppError)
+
 	UpsertMember(groupID string, userID string) (*model.GroupMember, *model.AppError)
 	DeleteMember(groupID string, userID string) (*model.GroupMember, *model.AppError)
 	PermanentDeleteMembersByUser(userId string) *model.AppError

store/storetest/group_store.go

@@ -32,6 +32,10 @@ func TestGroupStore(t *testing.T, ss store.Store) {
 
 	t.Run("GetMemberUsers", func(t *testing.T) { testGroupGetMemberUsers(t, ss) })
 	t.Run("GetMemberUsersPage", func(t *testing.T) { testGroupGetMemberUsersPage(t, ss) })
+
+	t.Run("GetMemberUsersInTeam", func(t *testing.T) { testGroupGetMemberUsersInTeam(t, ss) })
+	t.Run("GetMemberUsersNotInChannel", func(t *testing.T) { testGroupGetMemberUsersNotInChannel(t, ss) })
+
 	t.Run("UpsertMember", func(t *testing.T) { testUpsertMember(t, ss) })
 	t.Run("DeleteMember", func(t *testing.T) { testGroupDeleteMember(t, ss) })
 	t.Run("PermanentDeleteMembersByUser", func(t *testing.T) { testGroupPermanentDeleteMembersByUser(t, ss) })
@@ -682,6 +686,231 @@ func testGroupGetMemberUsersPage(t *testing.T, ss store.Store) {
 	require.Equal(t, 2, len(groupMembers))
 }
 
+func testGroupGetMemberUsersInTeam(t *testing.T, ss store.Store) {
+	// Save a team
+	team := &model.Team{
+		DisplayName: "Name",
+		Description: "Some description",
+		CompanyName: "Some company name",
+		Name:        "z-z-" + model.NewId() + "a",
+		Email:       "success+" + model.NewId() + "@simulator.amazonses.com",
+		Type:        model.TEAM_OPEN,
+	}
+	team, err := ss.Team().Save(team)
+	require.Nil(t, err)
+
+	// Save a group
+	g1 := &model.Group{
+		Name:        model.NewId(),
+		DisplayName: model.NewId(),
+		Description: model.NewId(),
+		Source:      model.GroupSourceLdap,
+		RemoteId:    model.NewId(),
+	}
+	group, err := ss.Group().Create(g1)
+	require.Nil(t, err)
+
+	u1 := &model.User{
+		Email:    MakeEmail(),
+		Username: model.NewId(),
+	}
+	user1, err := ss.User().Save(u1)
+	require.Nil(t, err)
+
+	_, err = ss.Group().UpsertMember(group.Id, user1.Id)
+	require.Nil(t, err)
+
+	u2 := &model.User{
+		Email:    MakeEmail(),
+		Username: model.NewId(),
+	}
+	user2, err := ss.User().Save(u2)
+	require.Nil(t, err)
+
+	_, err = ss.Group().UpsertMember(group.Id, user2.Id)
+	require.Nil(t, err)
+
+	u3 := &model.User{
+		Email:    MakeEmail(),
+		Username: model.NewId(),
+	}
+	user3, err := ss.User().Save(u3)
+	require.Nil(t, err)
+
+	_, err = ss.Group().UpsertMember(group.Id, user3.Id)
+	require.Nil(t, err)
+
+	// returns no members when team does not exist
+	groupMembers, err := ss.Group().GetMemberUsersInTeam(group.Id, "non-existant-channel-id")
+	require.Nil(t, err)
+	require.Equal(t, 0, len(groupMembers))
+
+	// returns no members when group has no members in the team
+	groupMembers, err = ss.Group().GetMemberUsersInTeam(group.Id, team.Id)
+	require.Nil(t, err)
+	require.Equal(t, 0, len(groupMembers))
+
+	m1 := &model.TeamMember{TeamId: team.Id, UserId: user1.Id}
+	_, err = ss.Team().SaveMember(m1, -1)
+	require.Nil(t, err)
+
+	// returns single member in team
+	groupMembers, err = ss.Group().GetMemberUsersInTeam(group.Id, team.Id)
+	require.Nil(t, err)
+	require.Equal(t, 1, len(groupMembers))
+
+	m2 := &model.TeamMember{TeamId: team.Id, UserId: user2.Id}
+	m3 := &model.TeamMember{TeamId: team.Id, UserId: user3.Id}
+	_, err = ss.Team().SaveMember(m2, -1)
+	require.Nil(t, err)
+	_, err = ss.Team().SaveMember(m3, -1)
+	require.Nil(t, err)
+
+	// returns all members when all members are in team
+	groupMembers, err = ss.Group().GetMemberUsersInTeam(group.Id, team.Id)
+	require.Nil(t, err)
+	require.Equal(t, 3, len(groupMembers))
+}
+
+func testGroupGetMemberUsersNotInChannel(t *testing.T, ss store.Store) {
+	// Save a team
+	team := &model.Team{
+		DisplayName: "Name",
+		Description: "Some description",
+		CompanyName: "Some company name",
+		Name:        "z-z-" + model.NewId() + "a",
+		Email:       "success+" + model.NewId() + "@simulator.amazonses.com",
+		Type:        model.TEAM_OPEN,
+	}
+	team, err := ss.Team().Save(team)
+	require.Nil(t, err)
+
+	// Save a group
+	g1 := &model.Group{
+		Name:        model.NewId(),
+		DisplayName: model.NewId(),
+		Description: model.NewId(),
+		Source:      model.GroupSourceLdap,
+		RemoteId:    model.NewId(),
+	}
+	group, err := ss.Group().Create(g1)
+	require.Nil(t, err)
+
+	u1 := &model.User{
+		Email:    MakeEmail(),
+		Username: model.NewId(),
+	}
+	user1, err := ss.User().Save(u1)
+	require.Nil(t, err)
+
+	_, err = ss.Group().UpsertMember(group.Id, user1.Id)
+	require.Nil(t, err)
+
+	u2 := &model.User{
+		Email:    MakeEmail(),
+		Username: model.NewId(),
+	}
+	user2, err := ss.User().Save(u2)
+	require.Nil(t, err)
+
+	_, err = ss.Group().UpsertMember(group.Id, user2.Id)
+	require.Nil(t, err)
+
+	u3 := &model.User{
+		Email:    MakeEmail(),
+		Username: model.NewId(),
+	}
+	user3, err := ss.User().Save(u3)
+	require.Nil(t, err)
+
+	_, err = ss.Group().UpsertMember(group.Id, user3.Id)
+	require.Nil(t, err)
+
+	// Create Channel
+	channel := &model.Channel{
+		TeamId:      team.Id,
+		DisplayName: "Channel",
+		Name:        model.NewId(),
+		Type:        model.CHANNEL_OPEN, // Query does not look at type so this shouldn't matter.
+	}
+	channel, err = ss.Channel().Save(channel, 9999)
+	require.Nil(t, err)
+
+	// returns no members when channel does not exist
+	groupMembers, err := ss.Group().GetMemberUsersNotInChannel(group.Id, "non-existant-channel-id")
+	require.Nil(t, err)
+	require.Equal(t, 0, len(groupMembers))
+
+	// returns no members when group has no members in the team that the channel belongs to
+	groupMembers, err = ss.Group().GetMemberUsersNotInChannel(group.Id, channel.Id)
+	require.Nil(t, err)
+	require.Equal(t, 0, len(groupMembers))
+
+	m1 := &model.TeamMember{TeamId: team.Id, UserId: user1.Id}
+	_, err = ss.Team().SaveMember(m1, -1)
+	require.Nil(t, err)
+
+	// returns single member in team and not in channel
+	groupMembers, err = ss.Group().GetMemberUsersNotInChannel(group.Id, channel.Id)
+	require.Nil(t, err)
+	require.Equal(t, 1, len(groupMembers))
+
+	m2 := &model.TeamMember{TeamId: team.Id, UserId: user2.Id}
+	m3 := &model.TeamMember{TeamId: team.Id, UserId: user3.Id}
+	_, err = ss.Team().SaveMember(m2, -1)
+	require.Nil(t, err)
+	_, err = ss.Team().SaveMember(m3, -1)
+	require.Nil(t, err)
+
+	// returns all members when all members are in team and not in channel
+	groupMembers, err = ss.Group().GetMemberUsersNotInChannel(group.Id, channel.Id)
+	require.Nil(t, err)
+	require.Equal(t, 3, len(groupMembers))
+
+	cm1 := &model.ChannelMember{
+		ChannelId:   channel.Id,
+		UserId:      user1.Id,
+		SchemeGuest: false,
+		SchemeUser:  true,
+		SchemeAdmin: false,
+		NotifyProps: model.GetDefaultChannelNotifyProps(),
+	}
+	_, err = ss.Channel().SaveMember(cm1)
+	require.Nil(t, err)
+
+	// returns both members not yet added to channel
+	groupMembers, err = ss.Group().GetMemberUsersNotInChannel(group.Id, channel.Id)
+	require.Nil(t, err)
+	require.Equal(t, 2, len(groupMembers))
+
+	cm2 := &model.ChannelMember{
+		ChannelId:   channel.Id,
+		UserId:      user2.Id,
+		SchemeGuest: false,
+		SchemeUser:  true,
+		SchemeAdmin: false,
+		NotifyProps: model.GetDefaultChannelNotifyProps(),
+	}
+	cm3 := &model.ChannelMember{
+		ChannelId:   channel.Id,
+		UserId:      user3.Id,
+		SchemeGuest: false,
+		SchemeUser:  true,
+		SchemeAdmin: false,
+		NotifyProps: model.GetDefaultChannelNotifyProps(),
+	}
+
+	_, err = ss.Channel().SaveMember(cm2)
+	require.Nil(t, err)
+	_, err = ss.Channel().SaveMember(cm3)
+	require.Nil(t, err)
+
+	// returns none when all members have been added to team and channel
+	groupMembers, err = ss.Group().GetMemberUsersNotInChannel(group.Id, channel.Id)
+	require.Nil(t, err)
+	require.Equal(t, 0, len(groupMembers))
+}
+
 func testUpsertMember(t *testing.T, ss store.Store) {
 	// Create group
 	g1 := &model.Group{

store/storetest/mocks/GroupStore.go

@@ -702,6 +702,56 @@ func (_m *GroupStore) GetMemberUsers(groupID string) ([]*model.User, *model.AppE
 	return r0, r1
 }
 
+// GetMemberUsersInTeam provides a mock function with given fields: groupID, teamID
+func (_m *GroupStore) GetMemberUsersInTeam(groupID string, teamID string) ([]*model.User, *model.AppError) {
+	ret := _m.Called(groupID, teamID)
+
+	var r0 []*model.User
+	if rf, ok := ret.Get(0).(func(string, string) []*model.User); ok {
+		r0 = rf(groupID, teamID)
+	} else {
+		if ret.Get(0) != nil {
+			r0 = ret.Get(0).([]*model.User)
+		}
+	}
+
+	var r1 *model.AppError
+	if rf, ok := ret.Get(1).(func(string, string) *model.AppError); ok {
+		r1 = rf(groupID, teamID)
+	} else {
+		if ret.Get(1) != nil {
+			r1 = ret.Get(1).(*model.AppError)
+		}
+	}
+
+	return r0, r1
+}
+
+// GetMemberUsersNotInChannel provides a mock function with given fields: groupID, channelID
+func (_m *GroupStore) GetMemberUsersNotInChannel(groupID string, channelID string) ([]*model.User, *model.AppError) {
+	ret := _m.Called(groupID, channelID)
+
+	var r0 []*model.User
+	if rf, ok := ret.Get(0).(func(string, string) []*model.User); ok {
+		r0 = rf(groupID, channelID)
+	} else {
+		if ret.Get(0) != nil {
+			r0 = ret.Get(0).([]*model.User)
+		}
+	}
+
+	var r1 *model.AppError
+	if rf, ok := ret.Get(1).(func(string, string) *model.AppError); ok {
+		r1 = rf(groupID, channelID)
+	} else {
+		if ret.Get(1) != nil {
+			r1 = ret.Get(1).(*model.AppError)
+		}
+	}
+
+	return r0, r1
+}
+
 // GetMemberUsersPage provides a mock function with given fields: groupID, page, perPage
 func (_m *GroupStore) GetMemberUsersPage(groupID string, page int, perPage int) ([]*model.User, *model.AppError) {
 	ret := _m.Called(groupID, page, perPage)

store/timer_layer.go

@@ -3054,6 +3054,38 @@ func (s *TimerLayerGroupStore) GetMemberUsers(groupID string) ([]*model.User, *m
 	return resultVar0, resultVar1
 }
 
+func (s *TimerLayerGroupStore) GetMemberUsersInTeam(groupID string, teamID string) ([]*model.User, *model.AppError) {
+	start := timemodule.Now()
+
+	resultVar0, resultVar1 := s.GroupStore.GetMemberUsersInTeam(groupID, teamID)
+
+	elapsed := float64(timemodule.Since(start)) / float64(timemodule.Second)
+	if s.Root.Metrics != nil {
+		success := "false"
+		if resultVar1 == nil {
+			success = "true"
+		}
+		s.Root.Metrics.ObserveStoreMethodDuration("GroupStore.GetMemberUsersInTeam", success, elapsed)
+	}
+	return resultVar0, resultVar1
+}
+
+func (s *TimerLayerGroupStore) GetMemberUsersNotInChannel(groupID string, channelID string) ([]*model.User, *model.AppError) {
+	start := timemodule.Now()
+
+	resultVar0, resultVar1 := s.GroupStore.GetMemberUsersNotInChannel(groupID, channelID)
+
+	elapsed := float64(timemodule.Since(start)) / float64(timemodule.Second)
+	if s.Root.Metrics != nil {
+		success := "false"
+		if resultVar1 == nil {
+			success = "true"
+		}
+		s.Root.Metrics.ObserveStoreMethodDuration("GroupStore.GetMemberUsersNotInChannel", success, elapsed)
+	}
+	return resultVar0, resultVar1
+}
+
 func (s *TimerLayerGroupStore) GetMemberUsersPage(groupID string, page int, perPage int) ([]*model.User, *model.AppError) {
 	start := timemodule.Now()