Skip re-setup when creating a child session

lib/irb.rb

@@ -1514,7 +1514,7 @@ class Binding
   # See IRB for more information.
   def irb(show_code: true)
     # Setup IRB with the current file's path and no command line arguments
-    IRB.setup(source_location[0], argv: [])
+    IRB.setup(source_location[0], argv: []) unless IRB.initialized?
     # Create a new workspace using the current binding
     workspace = IRB::WorkSpace.new(self)
     # Print the code around the binding if show_code is true

lib/irb/init.rb

@@ -6,6 +6,7 @@
 
 module IRB # :nodoc:
   @CONF = {}
+  @INITIALIZED = false
   # Displays current configuration.
   #
   # Modifying the configuration is achieved by sending a message to IRB.conf.
@@ -41,6 +42,10 @@ def IRB.version
     format("irb %s (%s)", @RELEASE_VERSION, @LAST_UPDATE_DATE)
   end
 
+  def IRB.initialized?
+    !!@INITIALIZED
+  end
+
   # initialize config
   def IRB.setup(ap_path, argv: ::ARGV)
     IRB.init_config(ap_path)
@@ -52,6 +57,7 @@ def IRB.setup(ap_path, argv: ::ARGV)
     unless @CONF[:PROMPT][@CONF[:PROMPT_MODE]]
       fail UndefinedPromptMode, @CONF[:PROMPT_MODE]
     end
+    @INITIALIZED = true
   end
 
   # @CONF default setting

test/irb/yamatanooroti/test_rendering.rb

@@ -49,6 +49,42 @@ def test_launch
     EOC
   end
 
+  def test_configuration_file_is_skipped_with_dash_f
+    write_irbrc <<~'LINES'
+      puts '.irbrc file should be ignored when -f is used'
+    LINES
+    start_terminal(25, 80, %W{ruby -I#{@pwd}/lib #{@pwd}/exe/irb -f}, startup_message: '')
+    write(<<~EOC)
+      'Hello, World!'
+    EOC
+    close
+    assert_screen(<<~EOC)
+      irb(main):001> 'Hello, World!'
+      => "Hello, World!"
+      irb(main):002>
+    EOC
+  end
+
+  def test_configuration_file_is_skipped_with_dash_f_for_nested_sessions
+    write_irbrc <<~'LINES'
+      puts '.irbrc file should be ignored when -f is used'
+    LINES
+    start_terminal(25, 80, %W{ruby -I#{@pwd}/lib #{@pwd}/exe/irb -f}, startup_message: '')
+    write(<<~EOC)
+      'Hello, World!'
+      binding.irb
+      exit!
+    EOC
+    close
+    assert_screen(<<~EOC)
+      irb(main):001> 'Hello, World!'
+      => "Hello, World!"
+      irb(main):002> binding.irb
+      irb(main):003> exit!
+      irb(main):001>
+    EOC
+  end
+
   def test_nomultiline
     write_irbrc <<~'LINES'
       puts 'start IRB'