use ProxyPattern to match for ActiveSupport::Notifications fanout/unsubscribe

[zvkemp]

Summary

Before this change, ActiveSupport::Notifications.unsubscribe would eagerly remove all subscribers for which subscriber.matches?(string) was true, which can cause some unintended behavior in the case of regexes or other compound matchers (in our case, we had a single listener subscribed to a few dozen event keys via a single pattern object that internally checked for inclusion within a set).

Unsubscribing to a single string should not negate any other potential matches for those subscriptions. After this change:

• [no change] unsubscribing via string for string-based subscriptions will reject the subscription from the array
• [no change] unsubscribing via subscriber reference removes that subscriber
• unsubscribing via string for subscriptions with the potential to match multiple values will append that string to a blacklist. This will in turn prevent that pattern from matching that string in the future, so the listener won't be added under that key to the listeners_for map.

[rails-bot]

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[dillonwelch]

Looks like there might have been some CodeClimate concerns but the analysis is out of date - can you merge in latest master so we can get an up to date build?

[zvkemp]

@oniofchaos I think there was an issue in master when the previous build ran. I rebased on latest master; everything looks green now!

[tenderlove]

@jhawthorn you've looked at this code recently. Any opinions?

[jhawthorn]

Can we use Set#include? instead? Since we know name and everything in the set to be a string

[tenderlove]

Can you change blacklist! to "restricted_list" or maybe restrict!.

[jhawthorn]

How about @unsubscribed?

[jhawthorn]

Other than two comments this looks good to me.

[zvkemp]

Thanks @jhawthorn and @tenderlove. I've implemented your suggested changes.

[tenderlove]

Thanks @jhawthorn and @tenderlove. I've implemented your suggested changes.

Great! Thank you!

[tenderlove]

I'll merge this once CI returns. 😄