Issue 7097 - Make element hiding filter objects ephemeral

lib/filterClasses.js

Index: lib/filterClasses.js
===================================================================
--- a/lib/filterClasses.js
+++ b/lib/filterClasses.js
@@ -76,16 +76,26 @@
    * @type {string}
    */
   get type()
   {
     throw new Error("Please define filter type in the subclass");
   },
 
   /**
+   * Whether this object is discarded after use. If <code>false</code>, the
+   * object is retained in memory once created and every call to
+   * {@link Filter#fromText} returns the same instance. Defaults to
+   * <code>false</code>.
+   * @type {boolean}
+   * @package
+   */
+  ephemeral: false,
+
+  /**
    * Subscriptions to which this filter belongs.
    * @type {?(Subscription|Set.<Subscription>)}
    * @private
    */
   _subscriptions: null,
 
   /**
    * Whether the filter's subscriptions have already been added to the filter.
@@ -179,16 +189,26 @@
       else if (subscription == this._subscriptions)
       {
         this._subscriptions = null;
       }
     }
   },
 
   /**
+   * Checks whether the filter should be serialized.
+   * @return {boolean}
+   * @protected
+   */
+  shouldSerialize()
+  {
+    return false;
+  },
+
+  /**
    * Serializes the filter for writing out on disk.
    * @yields {string}
    */
   *serialize()
   {
     let {text} = this;
 
     yield "[Filter]";
@@ -244,17 +264,19 @@
   {
     let match = text.includes("#") ? Filter.contentRegExp.exec(text) : null;
     if (match)
       filter = ContentFilter.fromText(text, match[1], match[2], match[3]);
     else
       filter = RegExpFilter.fromText(text);
   }
 
-  Filter.knownFilters.set(filter.text, filter);
+  if (!filter.ephemeral)
+    Filter.knownFilters.set(filter.text, filter);
+
   return filter;
 };
 
 /**
  * Deserializes a filter
  *
  * @param {Object}  obj map of serialized properties and their values
  * @return {Filter} filter or null if the filter couldn't be created
@@ -265,16 +287,21 @@
   if (filter instanceof ActiveFilter)
   {
     if ("disabled" in obj)
       filter._disabled = (obj.disabled == "true");
     if ("hitCount" in obj)
       filter._hitCount = parseInt(obj.hitCount, 10) || 0;
     if ("lastHit" in obj)
       filter._lastHit = parseInt(obj.lastHit, 10) || 0;
+
+    // If the filter object is ephemeral, we normally don't keep it, but if it
+    // has any state then we must.
+    if (filter.ephemeral && this.shouldSerialize())
+      Filter.knownFilters.set(filter.text, filter);
   }
   return filter;
 };
 
 /**
  * Removes unnecessary whitespaces from filter text, will only return null if
  * the input parameter is null.
  * @param {string} text
@@ -427,16 +454,20 @@
     return this._disabled;
   },
   set disabled(value)
   {
     if (value != this._disabled)
     {
       let oldValue = this._disabled;
       this._disabled = value;
+
+      if (value && this.ephemeral)

[Manish Jethani, 2018/11/18 03:29:12]

This could be optimized a little bit, but this property is never set in the
current extension. We are keeping it because it might get used in a future
version (see discussion in #7095).

[Manish Jethani, 2018/11/18 06:19:14]

Ignore, now removed.

+        Filter.knownFilters.set(this.text, this);
+
       filterNotifier.emit("filter.disabled", this, value, oldValue);
     }
     return this._disabled;
   },
 
   /**
    * Number of hits on the filter since the last reset
    * @type {number}
@@ -446,16 +477,20 @@
     return this._hitCount;
   },
   set hitCount(value)
   {
     if (value != this._hitCount)
     {
       let oldValue = this._hitCount;
       this._hitCount = value;
+
+      if (value && this.ephemeral)
+        Filter.knownFilters.set(this.text, this);
+
       filterNotifier.emit("filter.hitCount", this, value, oldValue);
     }
     return this._hitCount;
   },
 
   /**
    * Last time the filter had a hit (in milliseconds since the beginning of the
    * epoch)
@@ -466,16 +501,20 @@
     return this._lastHit;
   },
   set lastHit(value)
   {
     if (value != this._lastHit)
     {
       let oldValue = this._lastHit;
       this._lastHit = value;
+
+      if (value && this.ephemeral)
+        Filter.knownFilters.set(this.text, this);
+
       filterNotifier.emit("filter.lastHit", this, value, oldValue);
     }
     return this._lastHit;
   },
 
   /**
    * String that the domains property should be generated from
    * @type {?string}
@@ -666,25 +705,33 @@
   isGeneric()
   {
     let {sitekeys, domains} = this;
 
     return !(sitekeys && sitekeys.length) && (!domains || domains.get(""));
   },
 
   /**
+   * See Filter.shouldSerialize()
+   * @inheritdoc
+   */
+  shouldSerialize()

[Manish Jethani, 2018/11/18 03:29:12]

Note that this will always return false in the current extension.

[Manish Jethani, 2018/11/18 06:19:14]

Ignore, now removed.

An object created with Filter.fromObject is never ephemeral.

+  {
+    return this._disabled || this._hitCount || this._lastHit;
+  },
+
+  /**
    * See Filter.serialize()
    * @inheritdoc
    */
   *serialize()
   {
-    let {_disabled, _hitCount, _lastHit} = this;
-
-    if (_disabled || _hitCount || _lastHit)
+    if (this.shouldSerialize())
     {
+      let {_disabled, _hitCount, _lastHit} = this;
       yield* Filter.prototype.serialize.call(this);
       if (_disabled)
         yield "disabled=true";
       if (_hitCount)
         yield "hitCount=" + _hitCount;
       if (_lastHit)
         yield "lastHit=" + _lastHit;
     }
@@ -1311,17 +1358,23 @@
  */
 function ElemHideFilter(text, domains, selector)
 {
   ElemHideBase.call(this, text, domains, selector);
 }
 exports.ElemHideFilter = ElemHideFilter;
 
 ElemHideFilter.prototype = extend(ElemHideBase, {
-  type: "elemhide"
+  type: "elemhide",
+
+  /**
+   * See Filter.ephemeral
+   * @inheritdoc
+   */
+  ephemeral: true
 });
 
 /**
  * Class for element hiding exceptions
  * @param {string} text see {@link Filter Filter()}
  * @param {string} [domains]  see {@link ElemHideBase ElemHideBase()}
  * @param {string} selector see {@link ElemHideBase ElemHideBase()}
  * @constructor