Issue 5549 - Implement missing error handlings for custom filter lists

desktop-options.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-present eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 643 matching lines @@
         const filters = E("custom-filters-raw").value;
         sendMessageHandleErrors({
           type: "filters.importRaw",
           text: filters,
           removeExisting: true
         },
         (errors) =>
         {
           if (errors)
           {
+            E("custom-filters").classList.add("warning");
             const customFiltersError = clearAndGetCustomFiltersError();
-            E("custom-filters").classList.add("warning");
 
             // The current error does not contain info about the line
             // that generated such error.
             // Whenever the error object will pass the bad filter
             // within its properties, this split should be removed.
             const lines = filters.split("\n");
             const messages = errors.map(error => lines[error.lineno - 1]);
             for (const message of messages)
             {
               const li = document.createElement("li");
@@ skipping 94 matching lines @@
         else
         {
           form.querySelector(":invalid").focus();
         }
         break;
     }
   }
 
   function clearAndGetCustomFiltersError()
   {
-    E("custom-filters").classList.remove("warning");
     const customFiltersError = E("custom-filters-error");
     customFiltersError.textContent = "";
     customFiltersError.classList.remove("many");
     return customFiltersError;
   }
 
   function setCustomFiltersView(mode)
   {
     let customFiltersElement = E("custom-filters-raw");
     updateCustomFiltersUi();
     if (mode == "read")
     {
+      E("custom-filters").classList.remove("warning");
       clearAndGetCustomFiltersError();
       customFiltersElement.disabled = true;
       if (!customFiltersElement.value)
       {
         setCustomFiltersView("empty");
         return;
       }
     }
     else if (mode == "write")
     {
@@ skipping 699 matching lines @@
   });
   browser.runtime.sendMessage({
     type: "subscriptions.listen",
     filter: ["added", "disabled", "homepage", "lastDownload", "removed",
              "title", "downloadStatus", "downloading"]
   });
 
   window.addEventListener("DOMContentLoaded", onDOMLoaded, false);
   window.addEventListener("hashchange", onHashChange, false);
 }