MM-23770: Fix for blank DefaultChannelGuestRole on team schemes. (#14210)

* MM-23770: Fix for blank DefaultChannelGuestRole on team schemes.

* MM-23770: Adds test for an team scheme with a blank DefaultChannelGuestRole field.

* MM-23770: Fix for unexpected Schemes.Get.

api4/channel_test.go

@@ -13,6 +13,8 @@ import (
 	"time"
 
 	"github.com/mattermost/mattermost-server/v5/model"
+	"github.com/mattermost/mattermost-server/v5/plugin/plugintest/mock"
+	"github.com/mattermost/mattermost-server/v5/store/storetest/mocks"
 	"github.com/mattermost/mattermost-server/v5/utils"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
@@ -3138,6 +3140,34 @@ func TestGetChannelModerations(t *testing.T) {
 			}
 		}
 	})
+
+	t.Run("Does not return an error if the team scheme has a blank DefaultChannelGuestRole field", func(t *testing.T) {
+		scheme := th.SetupTeamScheme()
+		scheme.DefaultChannelGuestRole = ""
+
+		mockStore := mocks.Store{}
+		mockSchemeStore := mocks.SchemeStore{}
+		mockSchemeStore.On("Get", mock.Anything).Return(scheme, nil)
+		mockStore.On("Scheme").Return(&mockSchemeStore)
+		mockStore.On("Team").Return(th.App.Srv().Store.Team())
+		mockStore.On("Channel").Return(th.App.Srv().Store.Channel())
+		mockStore.On("User").Return(th.App.Srv().Store.User())
+		mockStore.On("Post").Return(th.App.Srv().Store.Post())
+		mockStore.On("FileInfo").Return(th.App.Srv().Store.FileInfo())
+		mockStore.On("Webhook").Return(th.App.Srv().Store.Webhook())
+		mockStore.On("System").Return(th.App.Srv().Store.System())
+		mockStore.On("License").Return(th.App.Srv().Store.License())
+		mockStore.On("Role").Return(th.App.Srv().Store.Role())
+		mockStore.On("Close").Return(nil)
+		th.App.Srv().Store = &mockStore
+
+		team.SchemeId = &scheme.Id
+		_, err := th.App.UpdateTeamScheme(team)
+		require.Nil(t, err)
+
+		_, res := th.SystemAdminClient.GetChannelModerations(channel.Id, "")
+		require.Nil(t, res.Error)
+	})
 }
 
 func TestPatchChannelModerations(t *testing.T) {

app/channel.go

@@ -698,26 +698,39 @@ func (a *App) GetTeamSchemeChannelRoles(teamId string) (guestRoleName, userRoleN
 
 // GetChannelModerationsForChannel Gets a channels ChannelModerations from either the higherScoped roles or from the channel scheme roles.
 func (a *App) GetChannelModerationsForChannel(channel *model.Channel) ([]*model.ChannelModeration, *model.AppError) {
-	guestRoleName, memberRoleName, _, _ := a.GetSchemeRolesForChannel(channel.Id)
+	guestRoleName, memberRoleName, _, err := a.GetSchemeRolesForChannel(channel.Id)
+	if err != nil {
+		return nil, err
+	}
+
 	memberRole, err := a.GetRoleByName(memberRoleName)
 	if err != nil {
 		return nil, err
 	}
 
-	guestRole, err := a.GetRoleByName(guestRoleName)
+	var guestRole *model.Role
+	if len(guestRoleName) > 0 {
+		guestRole, err = a.GetRoleByName(guestRoleName)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	higherScopedGuestRoleName, higherScopedMemberRoleName, _, err := a.GetTeamSchemeChannelRoles(channel.TeamId)
 	if err != nil {
 		return nil, err
 	}
-
-	higherScopedGuestRoleName, higherScopedMemberRoleName, _, _ := a.GetTeamSchemeChannelRoles(channel.TeamId)
 	higherScopedMemberRole, err := a.GetRoleByName(higherScopedMemberRoleName)
 	if err != nil {
 		return nil, err
 	}
 
-	higherScopedGuestRole, err := a.GetRoleByName(higherScopedGuestRoleName)
-	if err != nil {
-		return nil, err
+	var higherScopedGuestRole *model.Role
+	if len(guestRoleName) > 0 {
+		higherScopedGuestRole, err = a.GetRoleByName(higherScopedGuestRoleName)
+		if err != nil {
+			return nil, err
+		}
 	}
 
 	return buildChannelModerations(channel.Type, memberRole, guestRole, higherScopedMemberRole, higherScopedGuestRole), nil
@@ -821,10 +834,19 @@ func (a *App) PatchChannelModerationsForChannel(channel *model.Channel, channelM
 }
 
 func buildChannelModerations(channelType string, memberRole *model.Role, guestRole *model.Role, higherScopedMemberRole *model.Role, higherScopedGuestRole *model.Role) []*model.ChannelModeration {
-	memberPermissions := memberRole.GetChannelModeratedPermissions(channelType)
-	guestPermissions := guestRole.GetChannelModeratedPermissions(channelType)
-	higherScopedMemberPermissions := higherScopedMemberRole.GetChannelModeratedPermissions(channelType)
-	higherScopedGuestPermissions := higherScopedGuestRole.GetChannelModeratedPermissions(channelType)
+	var memberPermissions, guestPermissions, higherScopedMemberPermissions, higherScopedGuestPermissions map[string]bool
+	if memberRole != nil {
+		memberPermissions = memberRole.GetChannelModeratedPermissions(channelType)
+	}
+	if guestRole != nil {
+		guestPermissions = guestRole.GetChannelModeratedPermissions(channelType)
+	}
+	if higherScopedMemberRole != nil {
+		higherScopedMemberPermissions = higherScopedMemberRole.GetChannelModeratedPermissions(channelType)
+	}
+	if higherScopedGuestRole != nil {
+		higherScopedGuestPermissions = higherScopedGuestRole.GetChannelModeratedPermissions(channelType)
+	}
 
 	var channelModerations []*model.ChannelModeration
 	for _, permissionKey := range model.CHANNEL_MODERATED_PERMISSIONS {