Issue 5549 - Implement missing error handlings for custom filter lists

desktop-options.js

Index: desktop-options.js
===================================================================
--- a/desktop-options.js
+++ b/desktop-options.js
@@ -547,14 +547,17 @@
     return null;
   }
 
-  function sendMessageHandleErrors(message, onSuccess)
+  function sendMessageHandleErrors(message, callback)
   {
     browser.runtime.sendMessage(message, (errors) =>
     {
-      if (errors.length > 0)
-        alert(errors.join("\n"));
-      else if (onSuccess)
-        onSuccess();
+      if (callback)
+      {
+        if (errors.length > 0)
+          callback(errors);
+        else
+          callback();
+      }
     });
   }
 
@@ -648,14 +651,37 @@
         });
         break;
       case "save-custom-filters":
+        const filters = E("custom-filters-raw").value;
         sendMessageHandleErrors({
           type: "filters.importRaw",
-          text: E("custom-filters-raw").value,
+          text: filters,
           removeExisting: true
         },
-        () =>
+        (errors) =>
         {
-          setCustomFiltersView("read");
+          if (errors)
+          {
+            E("custom-filters").classList.add("warning");
+            const customFiltersError = clearAndGetCustomFiltersError();
+
+            // 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");
+              customFiltersError.appendChild(li).textContent = message;
+            }
+            if (errors.length > 5)
+              customFiltersError.classList.add("many");
+          }
+          else
+          {
+            setCustomFiltersView("read");
+          }
         });
         break;
       case "show-more-filters-section":
@@ -749,12 +775,22 @@
     }
   }
 
+  function clearAndGetCustomFiltersError()
+  {
+    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)
       {
@@ -918,10 +954,10 @@
     {
       setLinks("enable-acceptable-ads-description", link);
     });
-    setElementText(E("tracking-warning-1"), "options_tracking_warning_1", 
+    setElementText(E("tracking-warning-1"), "options_tracking_warning_1",
       [getMessage("common_feature_privacy_title"),
-      getMessage("options_acceptableAds_ads_label")]);
-    setElementText(E("tracking-warning-3"), "options_tracking_warning_3", 
+       getMessage("options_acceptableAds_ads_label")]);
+    setElementText(E("tracking-warning-3"), "options_tracking_warning_3",
       [getMessage("options_acceptableAds_privacy_label")]);
 
     getDocLink("privacy_friendly_ads", (link) =>
@@ -963,7 +999,8 @@
 
     getDocLink("filterdoc", (link) =>
     {
-      E("link-filters").setAttribute("href", link);
+      E("link-filters-1").setAttribute("href", link);
+      E("link-filters-2").setAttribute("href", link);
     });
 
     getDocLink("subscriptions", (link) =>
@@ -1295,7 +1332,7 @@
         updateSubscription(subscription);
         break;
       case "added":
-        let {url, recommended} = subscription;
+        let {url} = subscription;
         // Handle custom subscription
         if (/^~user/.test(url))
         {