Issue 5549 - Implement missing error handlings for custom filter lists

background.js

Index: background.js
===================================================================
--- a/background.js
+++ b/background.js
@@ -71,7 +71,6 @@
     blockedURLs: "",
     filterlistsReinitialized: false,
     addSubscription: false,
-    filterError: false,
     downloadStatus: "synchronize_ok",
     showNotificationUI: false,
     showPageOptions: false
@@ -313,7 +312,10 @@
   {
     this.text = text;
     this.disabled = false;
+    if (Filter.elemhideRegExp.test(text))
+      this.selector = RegExp.$3;
   }
+  Filter.elemhideRegExp = /^([^/*|@"!]*?)#([@?])?#(.+)$/;
   Filter.fromText = (text) => new Filter(text);
 
   function BlockingFilter()
@@ -331,24 +333,65 @@
     RegExpFilter
   };
 
+  const isValidCSSSelector = selector =>
+  {
+    if (!selector)
+      return true;
+    try
+    {
+      document.documentElement.matches(selector);
+      return true;
+    }
+    catch (error)
+    {
+      return false;
+    }
+  };
+
   modules.filterValidation =
   {
+    // to test failing filters
+    // use one or more bad CSS selectors
+    // or start the line with a [
     parseFilter(text)
     {
-      if (params.filterError)
-        return {error: "Invalid filter"};
-      return {filter: modules.filterClasses.Filter.fromText(text)};
+      let filter = null;
+      if (text)
+      {
+        if (text[0] == "[")
+          return {error: {reason: "Unexpected filter list header"}};
+
+        filter = modules.filterClasses.Filter.fromText(text);
+
+        if (!isValidCSSSelector(filter.selector))
+        {
+          return {error: {reason: "Invalid CSS selector"}};
+        }
+      }
+
+      return {filter};
     },
     parseFilters(text)
     {
-      if (params.filterError)
-        return {errors: ["Invalid filter"]};
-      return {
-        filters: text.split("\n")
-          .filter((filter) => !!filter)
-          .map(modules.filterClasses.Filter.fromText),
-        errors: []
-      };
+      let lines = text.split("\n");
+      let filters = [];
+      let errors = [];
+
+      for (let i = 0; i < lines.length; i++)
+      {
+        let {filter, error} = this.parseFilter(lines[i]);
+
+        if (filter)
+          filters.push(filter);
+
+        if (error)
+        {
+          error.lineno = i + 1;
+          errors.push(error);
+        }
+      }
+
+      return {filters, errors};
     }
   };