use a proxy matcher for AS::N fanout

2 files changed, 44 insertions, 3 deletions

diff --git a/activesupport/lib/active_support/notifications.rb b/activesupport/lib/active_support/notifications.rb
index 7ccc333463..d9e93b530c 100644
--- a/activesupport/lib/active_support/notifications.rb
+++ b/activesupport/lib/active_support/notifications.rb
@@ -153,6 +153,15 @@ module ActiveSupport
   #
   #   ActiveSupport::Notifications.unsubscribe("render")
   #
+  # Subscribers using a regexp or other pattern-matching object will remain subscribed
+  # to all events that match their original pattern, unless those events match a string
+  # passed to `unsubscribe`:
+  #
+  #   subscriber = ActiveSupport::Notifications.subscribe(/render/) { }
+  #   ActiveSupport::Notifications.unsubscribe('render_template.action_view')
+  #   subscriber.matches?('render_template.action_view') # => false
+  #   subscriber.matches?('render_partial.action_view') # => true
+  #
   # == Default Queue
   #
   # Notifications ships with a queue implementation that consumes and publishes events
diff --git a/activesupport/lib/active_support/notifications/fanout.rb b/activesupport/lib/active_support/notifications/fanout.rb
index 11721db103..f06504cf2c 100644
--- a/activesupport/lib/active_support/notifications/fanout.rb
+++ b/activesupport/lib/active_support/notifications/fanout.rb
@@ -2,6 +2,7 @@
 
 require "mutex_m"
 require "concurrent/map"
+require "set"
 
 module ActiveSupport
   module Notifications
@@ -39,6 +40,7 @@ module ActiveSupport
           when String
             @string_subscribers[subscriber_or_name].clear
             @listeners_for.delete(subscriber_or_name)
+            @other_subscribers.each { |sub| sub.unsubscribe!(subscriber_or_name) }
           else
             pattern = subscriber_or_name.try(:pattern)
             if String === pattern
@@ -113,11 +115,33 @@ module ActiveSupport
           end
         end
 
+        class Matcher #:nodoc:
+          attr_reader :pattern, :exclusions
+
+          def self.wrap(pattern)
+            return pattern if String === pattern
+            new(pattern)
+          end
+
+          def initialize(pattern)
+            @pattern = pattern
+            @exclusions = Set.new
+          end
+
+          def unsubscribe!(name)
+            exclusions << -name if pattern === name
+          end
+
+          def ===(name)
+            pattern === name && !exclusions.include?(name)
+          end
+        end
+
         class Evented #:nodoc:
           attr_reader :pattern
 
           def initialize(pattern, delegate)
-            @pattern = pattern
+            @pattern = Matcher.wrap(pattern)
             @delegate = delegate
             @can_publish = delegate.respond_to?(:publish)
           end
@@ -137,11 +161,15 @@ module ActiveSupport
           end
 
           def subscribed_to?(name)
-            @pattern === name
+            pattern === name
           end
 
           def matches?(name)
-            @pattern && @pattern === name
+            pattern && pattern === name
+          end
+
+          def unsubscribe!(name)
+            pattern.unsubscribe!(name)
           end
         end
 
@@ -204,6 +232,10 @@ module ActiveSupport
             true
           end
 
+          def unsubscribe!(*)
+            false
+          end
+
           alias :matches? :===
         end
       end