Issue 7097 - Make element hiding filter objects ephemeral

lib/subscriptionClasses.js

Index: lib/subscriptionClasses.js
===================================================================
--- a/lib/subscriptionClasses.js
+++ b/lib/subscriptionClasses.js
@@ -16,17 +16,17 @@
  */
 
 "use strict";
 
 /**
  * @fileOverview Definition of Subscription class and its subclasses.
  */
 
-const {ActiveFilter, BlockingFilter,
+const {Filter, ActiveFilter, BlockingFilter,
        WhitelistFilter, ElemHideBase} = require("./filterClasses");
 const {filterNotifier} = require("./filterNotifier");
 const {extend} = require("./coreUtils");
 
 /**
  * Abstract base class for filter subscriptions
  *
  * @param {string} url    download location of the subscription
@@ -163,27 +163,30 @@
   },
 
   /**
    * Yields the {@link Filter} object for each filter in the subscription.
    * @yields {Filter}
    */
   *filters()
   {
-    yield* this._filters;
+    for (let i = 0; i < this._filters.length; i++)
+      yield this._filters[i] || Filter.fromText(this._filterText[i], false);
   },
 
   /**
    * Returns the {@link Filter} object at the given 0-based index.
    * @param {number} index
    * @returns {?Filter}
    */
   filterAt(index)
   {
-    return this._filters[index] || null;
+    return this._filters[index] ||
+           (index >= 0 && index < this._filters.length ?
+              Filter.fromText(this._filterText[index], false) : null);
   },
 
   /**
    * Returns the 0-based index of the given filter.
    * @param {Filter} filter
    * @param {number} [fromIndex] The index from which to start the search.
    * @return {number}
    */
@@ -259,16 +262,22 @@
   },
 
   /**
    * Clears any in-memory caches held by the object.
    * @package
    */
   clearCaches()
   {
+    for (let i = 0; i < this._filters.length; i++)
+    {
+      if (this._filters[i] && this._filters[i].ephemeral)
+        this._filters[i] = null;
+    }
+
     this._filterTextLookup = null;
   },
 
   /**
    * Serializes the subscription for writing out on disk.
    * @yields {string}
    */
   *serialize()