Whispering backport for Action Cable

lib/anycable/rails/action_cable_ext/channel.rb

@@ -24,6 +24,11 @@ def stop_periodic_timers
 
   def stream_from(broadcasting, _callback = nil, **opts)
     whispering = opts.delete(:whisper)
+    if whispering
+      self.class.state_attr_accessor(:whisper_stream) unless respond_to?(:whisper_stream)
+      self.whisper_stream = broadcasting
+    end
+
     return super unless anycabled?
 
     broadcasting = String(broadcasting)
@@ -50,6 +55,12 @@ def stop_all_streams
     connection.anycable_socket.unsubscribe_from_all identifier
   end
 
+  def whisper(payload)
+    return unless whisper_stream
+
+    broadcast_to whisper_stream, payload
+  end
+
   private
 
   def anycabled?

lib/anycable/rails/action_cable_ext/whisper_stream.rb

@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+
+require "action_cable"
+
+ActionCable::Connection::Subscriptions.prepend(Module.new do
+  def execute_command(data)
+    return whisper(data) if data["command"] == "whisper"
+
+    super
+  end
+
+  def whisper(data)
+    find(data).whisper(ActiveSupport::JSON.decode(data["data"]))
+  end
+end)

lib/anycable/rails/ext.rb

@@ -5,6 +5,7 @@ module Rails
     module Ext
       autoload :JWT, "anycable/rails/ext/jwt"
       autoload :SignedStreams, "anycable/rails/ext/signed_streams"
+      autoload :WhisperStreams, "anycable/rails/ext/whisper_stream"
     end
   end
 end