Allow alternative schemes in Binder (puma#3302 )

lib/puma/binder.rb

@@ -141,7 +141,14 @@ def synthesize_binds_from_activated_fs(binds, only_matching)
       end
     end
 
+    def before_parse(&block)
+      @before_parse ||= []
+      @before_parse << block if block
+      @before_parse
+    end
+
     def parse(binds, log_writer = nil, log_msg = 'Listening')
+      before_parse.each(&:call)
       log_writer ||= @log_writer
       binds.each do |str|
         uri = URI.parse str

test/test_binder.rb

@@ -79,6 +79,20 @@ def test_synthesize_binds_from_activated_fds_complex_binds
     assert_equal expected, result
   end
 
+  def test_runs_before_parse_hooks
+    mock = Minitest::Mock.new
+    proc = -> { mock.call }
+
+    @binder.before_parse &proc
+
+    mock.expect(:call, nil)
+
+    @binder.parse ["tcp://localhost:0"]
+
+    mock.verify
+    assert_equal @binder.instance_variable_get(:@before_parse), [proc]
+  end
+
   def test_localhost_addresses_dont_alter_listeners_for_tcp_addresses
     @binder.parse ["tcp://localhost:0"], @log_writer