Issue 6193 - Allow element hiding emulation exceptions

lib/filterValidation.js

Index: lib/filterValidation.js
===================================================================
--- a/lib/filterValidation.js
+++ b/lib/filterValidation.js
@@ -14,18 +14,18 @@
  * You should have received a copy of the GNU General Public License
  * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
  */
 
 /** @module filterValidation */
 
 "use strict";
 
-const {Filter, InvalidFilter, ElemHideBase, ElemHideEmulationFilter} =
-      require("filterClasses");
+const {Filter, InvalidFilter, ElemHideBase, ElemHideException,
+       ElemHideEmulationFilter} = require("filterClasses");
 
 /**
  * An error returned by
  * {@link module:filterValidation.parseFilter parseFilter()} or
  * {@link module:filterValidation.parseFilters parseFilters()}
  * indicating that a given filter cannot be parsed,
  * contains an invalid CSS selector or is a filter list header.
  *
@@ -105,16 +105,37 @@
   }
   catch (e)
   {
     return false;
   }
   return true;
 }
 
+function isValidFilterSelector(filter)
+{
+  // Only ElemHideBase has selectors.
+  if (!(filter instanceof ElemHideBase))
+    return true;
+
+  // We don't check the syntax of ElemHideEmulationFilter yet.
+  if (filter instanceof ElemHideEmulationFilter)
+    return true;
+
+  // If it is an ElemHideException, and it has an extended CSS
+  // selector we don't validate and assume it is valid.
+  if (filter instanceof ElemHideException &&
+      filter.selector.includes(":-abp-"))
+  {
+    return true;
+  }
+
+  return isValidCSSSelector(filter.selector);
+}
+
 /**
  * @typedef ParsedFilter
  * @property {?Filter} [filter]
  *   The parsed filter if it is valid. Or null if the given string is empty.
  * @property {FilterParsingError} [error]
  *   See {@link module:filterValidation~FilterParsingError FilterParsingError}
  */
 
@@ -137,19 +158,17 @@
 
     filter = Filter.fromText(text);
 
     if (filter instanceof InvalidFilter)
     {
       return {error: new FilterParsingError("invalid-filter",
                                             {reason: filter.reason})};
     }
-    if (filter instanceof ElemHideBase &&
-        !(filter instanceof ElemHideEmulationFilter) &&
-        !isValidCSSSelector(filter.selector))
+    if (!isValidFilterSelector(filter))
     {
       return {error: new FilterParsingError("invalid-css-selector",
                                             {selector: filter.selector})};
     }
   }
 
   return {filter};
 };