MM-11230: Make permissions checks in commands failsafe. (#9392)

Also add additional unit tests to make sure the permissions tests are
completely solid.

app/command_channel_header.go

@@ -4,9 +4,9 @@
 package app
 
 import (
-	"github.com/mattermost/mattermost-server/model"
-
 	goi18n "github.com/nicksnyder/go-i18n/i18n"
+
+	"github.com/mattermost/mattermost-server/model"
 )
 
 type HeaderProvider struct {
@@ -37,33 +37,51 @@ func (me *HeaderProvider) GetCommand(a *App, T goi18n.TranslateFunc) *model.Comm
 func (me *HeaderProvider) DoCommand(a *App, args *model.CommandArgs, message string) *model.CommandResponse {
 	channel, err := a.GetChannel(args.ChannelId)
 	if err != nil {
-		return &model.CommandResponse{Text: args.T("api.command_channel_header.channel.app_error"), ResponseType: model.COMMAND_RESPONSE_TYPE_EPHEMERAL}
+		return &model.CommandResponse{
+			Text:         args.T("api.command_channel_header.channel.app_error"),
+			ResponseType: model.COMMAND_RESPONSE_TYPE_EPHEMERAL,
+		}
 	}
 
 	switch channel.Type {
 	case model.CHANNEL_OPEN:
 		if !a.SessionHasPermissionToChannel(args.Session, args.ChannelId, model.PERMISSION_MANAGE_PUBLIC_CHANNEL_PROPERTIES) {
-			return &model.CommandResponse{Text: args.T("api.command_channel_header.permission.app_error"), ResponseType: model.COMMAND_RESPONSE_TYPE_EPHEMERAL}
+			return &model.CommandResponse{
+				Text:         args.T("api.command_channel_header.permission.app_error"),
+				ResponseType: model.COMMAND_RESPONSE_TYPE_EPHEMERAL,
+			}
 		}
 
 	case model.CHANNEL_PRIVATE:
 		if !a.SessionHasPermissionToChannel(args.Session, args.ChannelId, model.PERMISSION_MANAGE_PRIVATE_CHANNEL_PROPERTIES) {
-			return &model.CommandResponse{Text: args.T("api.command_channel_header.permission.app_error"), ResponseType: model.COMMAND_RESPONSE_TYPE_EPHEMERAL}
+			return &model.CommandResponse{
+				Text:         args.T("api.command_channel_header.permission.app_error"),
+				ResponseType: model.COMMAND_RESPONSE_TYPE_EPHEMERAL,
+			}
 		}
 
 	case model.CHANNEL_GROUP, model.CHANNEL_DIRECT:
 		// Modifying the header is not linked to any specific permission for group/dm channels, so just check for membership.
 		channelMember, err := a.GetChannelMember(args.ChannelId, args.Session.UserId)
 		if err != nil || channelMember == nil {
-			return &model.CommandResponse{Text: args.T("api.command_channel_header.permission.app_error"), ResponseType: model.COMMAND_RESPONSE_TYPE_EPHEMERAL}
+			return &model.CommandResponse{
+				Text:         args.T("api.command_channel_header.permission.app_error"),
+				ResponseType: model.COMMAND_RESPONSE_TYPE_EPHEMERAL,
+			}
 		}
 
 	default:
-		return &model.CommandResponse{Text: args.T("api.command_channel_header.permission.app_error"), ResponseType: model.COMMAND_RESPONSE_TYPE_EPHEMERAL}
+		return &model.CommandResponse{
+			Text:         args.T("api.command_channel_header.permission.app_error"),
+			ResponseType: model.COMMAND_RESPONSE_TYPE_EPHEMERAL,
+		}
 	}
 
 	if len(message) == 0 {
-		return &model.CommandResponse{Text: args.T("api.command_channel_header.message.app_error"), ResponseType: model.COMMAND_RESPONSE_TYPE_EPHEMERAL}
+		return &model.CommandResponse{
+			Text:         args.T("api.command_channel_header.message.app_error"),
+			ResponseType: model.COMMAND_RESPONSE_TYPE_EPHEMERAL,
+		}
 	}
 
 	patch := &model.ChannelPatch{
@@ -73,7 +91,10 @@ func (me *HeaderProvider) DoCommand(a *App, args *model.CommandArgs, message str
 
 	_, err = a.PatchChannel(channel, patch, args.UserId)
 	if err != nil {
-		return &model.CommandResponse{Text: args.T("api.command_channel_header.update_channel.app_error"), ResponseType: model.COMMAND_RESPONSE_TYPE_EPHEMERAL}
+		return &model.CommandResponse{
+			Text:         args.T("api.command_channel_header.update_channel.app_error"),
+			ResponseType: model.COMMAND_RESPONSE_TYPE_EPHEMERAL,
+		}
 	}
 
 	return &model.CommandResponse{}