PLT-7789: Fix raciness on Aurora with importing team members. (#7573)

* PLT-7789: Fix raciness on Aurora with importing team members.

* Fix and document return values.

app/import.go

@@ -773,18 +773,14 @@ func (a *App) ImportUserTeams(username string, data *[]UserTeamImportData) *mode
 			roles = *tdata.Roles
 		}
 
-		if _, err := a.joinUserToTeam(team, user); err != nil {
+		var member *model.TeamMember
+		if member, _, err = a.joinUserToTeam(team, user); err != nil {
 			return err
 		}
 
-		var member *model.TeamMember
+		if member.Roles != roles {
-		if member, err = a.GetTeamMember(team.Id, user.Id); err != nil {
+			if _, err := a.UpdateTeamMemberRoles(team.Id, user.Id, roles); err != nil {
-			return err
+				return err
-		} else {
-			if member.Roles != roles {
-				if _, err := a.UpdateTeamMemberRoles(team.Id, user.Id, roles); err != nil {
-					return err
-				}
 			}
 		}
 

app/team.go

@@ -273,7 +273,11 @@ func (a *App) AddUserToTeamByInviteId(inviteId string, userId string) (*model.Te
 	return team, nil
 }
 
-func (a *App) joinUserToTeam(team *model.Team, user *model.User) (bool, *model.AppError) {
+// Returns three values:
+// 1. a pointer to the team member, if successful
+// 2. a boolean: true if the user has a non-deleted team member for that team already, otherwise false.
+// 3. a pointer to an AppError if something went wrong.
+func (a *App) joinUserToTeam(team *model.Team, user *model.User) (*model.TeamMember, bool, *model.AppError) {
 	tm := &model.TeamMember{
 		TeamId: team.Id,
 		UserId: user.Id,
@@ -285,29 +289,31 @@ func (a *App) joinUserToTeam(team *model.Team, user *model.User) (bool, *model.A
 	}
 
 	if etmr := <-a.Srv.Store.Team().GetMember(team.Id, user.Id); etmr.Err == nil {
-		// Membership alredy exists.  Check if deleted and and update, otherwise do nothing
+		// Membership already exists.  Check if deleted and and update, otherwise do nothing
 		rtm := etmr.Data.(*model.TeamMember)
 
 		// Do nothing if already added
 		if rtm.DeleteAt == 0 {
-			return true, nil
+			return rtm, true, nil
 		}
 
 		if tmr := <-a.Srv.Store.Team().UpdateMember(tm); tmr.Err != nil {
-			return false, tmr.Err
+			return nil, false, tmr.Err
+		} else {
+			return tmr.Data.(*model.TeamMember), false, nil
 		}
 	} else {
 		// Membership appears to be missing.  Lets try to add.
 		if tmr := <-a.Srv.Store.Team().SaveMember(tm); tmr.Err != nil {
-			return false, tmr.Err
+			return nil, false, tmr.Err
+		} else {
+			return tmr.Data.(*model.TeamMember), false, nil
 		}
 	}
-
-	return false, nil
 }
 
 func (a *App) JoinUserToTeam(team *model.Team, user *model.User, userRequestorId string) *model.AppError {
-	if alreadyAdded, err := a.joinUserToTeam(team, user); err != nil {
+	if _, alreadyAdded, err := a.joinUserToTeam(team, user); err != nil {
 		return err
 	} else if alreadyAdded {
 		return nil