fix: reset timeout callbacks when requests are routed to a different connection

this may happen in a few contexts, such as connection exhaustion, but more importantly, when a request is retried in a different connection; if the request successfully sets the callbacks before the connection raises an issue and the request is retried in a new one, the callback from the faulty connection are carried with it, and triggered at a time when the connection is back in the connection pool, or worse, used in a different thread

this fix relies on :idle transition callback, which is called before request is routed around

lib/httpx/callbacks.rb

@@ -4,7 +4,7 @@ module HTTPX
   module Callbacks
     def on(type, &action)
       callbacks(type) << action
-      self
+      action
     end
 
     def once(type, &block)
@@ -12,7 +12,6 @@ module HTTPX
         block.call(*args, &callback)
         :delete
       end
-      self
     end
 
     def emit(type, *args)

lib/httpx/connection.rb

@@ -903,13 +903,13 @@ module HTTPX
     end
 
     def set_request_timeout(label, request, timeout, start_event, finish_events, &callback)
-      request.once(start_event) do
+      request.set_timeout_callback(start_event) do
         timer = @current_selector.after(timeout, callback)
         request.active_timeouts << label
 
         Array(finish_events).each do |event|
           # clean up request timeouts if the connection errors out
-          request.once(event) do
+          request.set_timeout_callback(event) do
             timer.cancel
             request.active_timeouts.delete(label)
           end

lib/httpx/plugins/callbacks.rb

@@ -25,6 +25,7 @@ module HTTPX
           class_eval(<<-MOD, __FILE__, __LINE__ + 1)
             def on_#{meth}(&blk)   # def on_connection_opened(&blk)
               on(:#{meth}, &blk)   #   on(:connection_opened, &blk)
+              self                 #   self
             end                    # end
           MOD
         end

lib/httpx/plugins/circuit_breaker.rb

@@ -36,6 +36,7 @@ module HTTPX
           class_eval(<<-MOD, __FILE__, __LINE__ + 1)
         def on_#{meth}(&blk)   # def on_circuit_open(&blk)
           on(:#{meth}, &blk)   #   on(:circuit_open, &blk)
+          self                 #   self
         end                    # end
           MOD
         end

lib/httpx/request.rb

@@ -284,6 +284,15 @@ module HTTPX
     def expects?
       @headers["expect"] == "100-continue" && @informational_status == 100 && !@response
     end
+
+    def set_timeout_callback(event, &callback)
+      clb = once(event, &callback)
+
+      # reset timeout callbacks when requests get rerouted to a different connection
+      once(:idle) do
+        callbacks(event).delete(clb)
+      end
+    end
   end
 end
 

sig/callbacks.rbs

@@ -4,8 +4,8 @@ module HTTPX
   end
 
   module Callbacks
-    def on: (Symbol) { (*untyped) -> void } -> self
-    def once: (Symbol) { (*untyped) -> void } -> self
+    def on: (Symbol) { (*untyped) -> void } -> ^(*untyped) -> void
+    def once: (Symbol) { (*untyped) -> void } -> ^(*untyped) -> void
     def emit: (Symbol, *untyped) -> void
 
     def callbacks_for?: (Symbol) -> bool

sig/request.rbs

@@ -64,6 +64,8 @@ module HTTPX
 
     def request_timeout: () -> Numeric?
 
+    def set_timeout_callback: (Symbol event) { (*untyped) -> void } -> void
+
     private
 
     def initialize_body: (Options options) -> Transcoder::_Encoder?