patching the setup of the on close callback instead

the previous patch allowed the callback to be called only once, whereas this one will be long-lived for the duration of the connection

lib/httpx/session.rb

@@ -260,7 +260,9 @@ def init_connection(type, uri, options)
       connection.on(:open) do
         emit(:connection_opened, connection.origin, connection.io.socket)
         # only run close callback if it opened
-        connection.once(:close) { emit(:connection_closed, connection.origin, connection.io.socket) }
+      end
+      connection.on(:close) do
+        emit(:connection_closed, connection.origin, connection.io.socket) if connection.used?
       end
       catch(:coalesced) do
         pool.init_connection(connection, options)

regression_tests/bug_1_1_1_test.rb

@@ -0,0 +1,30 @@
+# frozen_string_literal: true
+
+require "test_helper"
+require "support/http_helpers"
+
+class Bug_1_1_1_Test < Minitest::Test
+  include HTTPHelpers
+
+  def test_conection_callbacks_fire_setup_once
+    uri = build_uri("/get")
+
+    connected = 0
+
+    HTTPX.on_connection_opened { |*| connected += 1 }
+         .on_connection_closed { |*| connected -= 1 }
+         .wrap do |session|
+      3.times.each do
+        response = session.get(uri)
+        verify_status(response, 200)
+        assert connected.zero?
+      end
+    end
+  end
+
+  private
+
+  def scheme
+    "http://"
+  end
+end