CloudStorage: log error (#7694)

References <https://github.com/koreader/koreader/issues/7688>.

frontend/apps/cloudstorage/cloudstorage.lua

@@ -11,6 +11,7 @@ local Menu = require("ui/widget/menu")
 local UIManager = require("ui/uimanager")
 local WebDav = require("apps/cloudstorage/webdav")
 local lfs = require("libs/libkoreader-lfs")
+local logger = require("logger")
 local T = require("ffi/util").template
 local _ = require("gettext")
 local Screen = require("device").screen
@@ -147,28 +148,29 @@ function CloudStorage:selectCloudType()
 end
 
 function CloudStorage:openCloudServer(url)
-    local tbl
+    local tbl, e
     local NetworkMgr = require("ui/network/manager")
     if self.type == "dropbox" then
         if NetworkMgr:willRerunWhenOnline(function() self:openCloudServer(url) end) then
             return
         end
-        tbl = DropBox:run(url, self.password, self.choose_folder_mode)
+        tbl, e = DropBox:run(url, self.password, self.choose_folder_mode)
     elseif self.type == "ftp" then
         if NetworkMgr:willRerunWhenConnected(function() self:openCloudServer(url) end) then
             return
         end
-        tbl = Ftp:run(self.address, self.username, self.password, url)
+        tbl, e = Ftp:run(self.address, self.username, self.password, url)
     elseif self.type == "webdav" then
         if NetworkMgr:willRerunWhenConnected(function() self:openCloudServer(url) end) then
             return
         end
-        tbl = WebDav:run(self.address, self.username, self.password, url)
+        tbl, e = WebDav:run(self.address, self.username, self.password, url)
     end
     if tbl and #tbl > 0 then
         self:switchItemTable(url, tbl)
         return true
     elseif not tbl then
+        logger.err("CloudStorage:", e)
         UIManager:show(InfoMessage:new{
             text = _("Cannot fetch list of folder contents\nPlease check your configuration or network connection."),
             timeout = 3,

frontend/apps/cloudstorage/ftpapi.lua

@@ -39,8 +39,10 @@ function FtpApi:listFolder(address_path, folder_path)
     local file_name
     local tbl = {}
     local sink = ltn12.sink.table(tbl)
-    local ls_ftp = self:ftpGet(address_path, "nlst", sink)
-    if ls_ftp == nil then return false end
+    local ls_ftp, e = self:ftpGet(address_path, "nlst", sink)
+    if ls_ftp == nil then
+        return false, e
+    end
     if folder_path == "/" then
         folder_path = ""
     end