Issue 4450 - Prevent ElemHide filters with empty domains

lib/elemHide.js

Index: lib/elemHide.js
diff --git a/lib/elemHide.js b/lib/elemHide.js
index b9d34e3064d0f7a76252505a8a670d3ed55f8d92..948f62aaa1c8b0af54dd57ef4b31008a03aff729 100644
--- a/lib/elemHide.js
+++ b/lib/elemHide.js
@@ -43,23 +43,22 @@ var keyByFilter = Object.create(null);
 var filtersByDomain = Object.create(null);
 
 /**
- * Lookup table, filter keys by selector. (Only contains filters that have a
- * selector that is unconditionally matched for all domains.)
+ * Lookup table, filter key by selector. (Only used for selectors that are
+ * unconditionally matched for all domains.)
  */
-var filterKeysBySelector = Object.create(null);
+var filterKeyBySelector = Object.create(null);
 
 /**
- * This array caches the keys of filterKeysBySelector table (selectors which
+ * This array caches the keys of filterKeyBySelector table (selectors which
  * unconditionally apply on all domains). It will be null if the cache needs to
  * be rebuilt.
  */
 var unconditionalSelectors = null;
 
 /**
- * This array caches the values of filterKeysBySelector table (filterIds for
+ * This array caches the values of filterKeyBySelector table (filterIds for
  * selectors which unconditionally apply on all domains). It will be null if the
- * cache needs to be rebuilt. Note: Only the first filter key for each selector
- * is cached.
+ * cache needs to be rebuilt.
  */
 var unconditionalFilterKeys = null;
 
@@ -95,7 +94,7 @@ var ElemHide = exports.ElemHide =
     filterByKey = [];
     keyByFilter = Object.create(null);
     filtersByDomain = Object.create(null);
-    filterKeysBySelector = Object.create(null);
+    filterKeyBySelector = Object.create(null);
     unconditionalSelectors = unconditionalFilterKeys = null;
     knownExceptions = Object.create(null);
     exceptions = Object.create(null);
@@ -137,12 +136,11 @@ var ElemHide = exports.ElemHide =
       // If this is the first exception for a previously unconditionally
       // applied element hiding selector we need to take care to update the
       // lookups.
-      let filterKeys = filterKeysBySelector[selector];
-      if (filterKeys)
+      let filterKey = filterKeyBySelector[selector];
+      if (filterKey)
       {
-        for (let filterKey of filterKeys)
-          this._addToFiltersByDomain(filterKey, filterByKey[filterKey]);
-        delete filterKeysBySelector[selector];
+        this._addToFiltersByDomain(filterKey, filterByKey[filterKey]);
+        delete filterKeyBySelector[selector];
         unconditionalSelectors = unconditionalFilterKeys = null;
       }
 
@@ -159,16 +157,8 @@ var ElemHide = exports.ElemHide =
       if (!(filter.domains || filter.selector in exceptions))
       {
         // The new filter's selector is unconditionally applied to all domains
-        let filterKeys = filterKeysBySelector[filter.selector];
-        if (filterKeys)
-        {
-          filterKeys.push(key);
-        }
-        else
-        {
-          filterKeysBySelector[filter.selector] = [key];
-          unconditionalSelectors = unconditionalFilterKeys = null;
-        }
+        filterKeyBySelector[filter.selector] = key;
+        unconditionalSelectors = unconditionalFilterKeys = null;
       }
       else
       {
@@ -182,25 +172,11 @@ var ElemHide = exports.ElemHide =
 
   _removeFilterKey: function(key, filter)
   {
-    let filterKeys = filterKeysBySelector[filter.selector];
-    if (filterKeys)
+    if (filterKeyBySelector[filter.selector] == key)
     {
-      let index = filterKeys.indexOf(key);
-      if (index >= 0)
-      {
-        if (filterKeys.length > 1)
-        {
-          filterKeys.splice(index, 1);
-          if (index == 0)
-            unconditionalFilterKeys = null;
-        }
-        else
-        {
-          delete filterKeysBySelector[filter.selector];
-          unconditionalSelectors = unconditionalFilterKeys = null;
-        }
-        return;
-      }
+      delete filterKeyBySelector[filter.selector];
+      unconditionalSelectors = unconditionalFilterKeys = null;
+      return;
     }
 
     // We haven't found this filter in unconditional filters, look in
@@ -304,7 +280,7 @@ var ElemHide = exports.ElemHide =
   getUnconditionalSelectors: function()
   {
     if (!unconditionalSelectors)
-      unconditionalSelectors = Object.keys(filterKeysBySelector);
+      unconditionalSelectors = Object.keys(filterKeyBySelector);
     return unconditionalSelectors.slice();
   },
 
@@ -320,7 +296,7 @@ var ElemHide = exports.ElemHide =
       let selectors = this.getUnconditionalSelectors();
       unconditionalFilterKeys = [];
       for (let selector of selectors)
-        unconditionalFilterKeys.push(filterKeysBySelector[selector][0]);
+        unconditionalFilterKeys.push(filterKeyBySelector[selector]);
     }
     return unconditionalFilterKeys.slice();
   },