Issue 6829 - Free filters when subscriptions are empty

lib/filterStorage.js

Index: lib/filterStorage.js
===================================================================
--- a/lib/filterStorage.js
+++ b/lib/filterStorage.js
@@ -673,17 +673,21 @@
  * @param {Subscription} subscription filter subscription to be removed
  */
 function removeSubscriptionFilters(subscription)
 {
   if (!FilterStorage.knownSubscriptions.has(subscription.url))
     return;
 
   for (let filter of subscription.filters)
+  {
     filter.subscriptions.delete(subscription);
+    if (filter.subscriptions.size == 0)

[Manish Jethani, 2018/08/25 15:03:38]

removeSubscriptionFilters is also called from updateSubscriptionFilters, which
means this will also remove any filters that are also in the new list of filters
(passed to updateSubscriptionFilters). I think we should do this outside of this
function, where it is being called instead.

[jsonesen, 2018/08/25 15:18:46]

The deletion should I ly occur if there are no subs riptions in the subs set,
rather than if there are disabled subscriptions so I would think it shouldn't
effect the update and in fact should only occur when the filter has no
subscriptions (hence the logical if) also the filters are already being iterated
over here so we can avoid looking at all the filters again.

[jsonesen, 2018/08/25 15:32:08]

Oh shoot nevermind, since it removes first then adds the chance of having a
filter with 0 subscriptions that is meant to be added to the update subscription
is basically 100%?

[Manish Jethani, 2018/08/26 15:56:19]

Yes, exactly. If a filter is also in a different subscription then the count
will be greater than 0, but if it's only in this subscription then it'll be 0.

+      Filter.knownFilters.delete(filter.text);

[Jon Sonesen, 2018/08/21 21:50:41]

I found that there is a pretty good reduction in the memory footprint of the
extension. With this change; after removing all subscriptions from the options
page it would return to around 60mb with nothing but the options page open in
the browser. Whereas if you test without this, the footprint never really seems
to return to as small of a footprint as when first starting the extension with
no subscriptions.

+  }
 }
 
 /**
  * Listener returned by FilterStorage.importData(), parses filter data.
  * @constructor
  */
 function INIParser()
 {