Save irb:debug's history

lib/irb.rb

@@ -386,7 +386,18 @@ def self.debug_readline(binding:, irb:)
     # 2. Any input that's not irb-command, like `foo = 123`
     #
     # Irb#eval_input will simply return the input, and we need to pass it to the debugger.
-    input = irb.eval_input
+    input = if conf[:SAVE_HISTORY] && irb.context.io.support_history_saving?
+      # Previous IRB session's history has been saved when `Irb#run` is exited
+      # We need to clear the old history before we start debugging, so it's not written again
+      irb.context.io.clear_history
+      begin
+        irb.eval_input
+      ensure
+        irb.context.io.save_history
+      end
+    else
+      irb.eval_input
+    end
 
     if input&.include?("\n")
       irb.scanner.increase_line_no(input.count("\n") - 1)

lib/irb/history.rb

@@ -4,6 +4,11 @@ def support_history_saving?
       true
     end
 
+    def clear_history
+      self.class::HISTORY.clear
+      @loaded_history_lines = 0 if defined? @loaded_history_lines
+    end
+
     def load_history
       history = self.class::HISTORY
       if history_file = IRB.conf[:HISTORY_FILE]

test/irb/test_history.rb

@@ -209,7 +209,40 @@ def with_temp_stdio
     end
   end
 
-  class NestedIRBHistoryTest < IntegrationTestCase
+  class IRBHistoryIntegrationTest < IntegrationTestCase
+    def test_history_saving_with_debug
+      write_history ""
+
+      write_ruby <<~'RUBY'
+        def foo
+        end
+
+        binding.irb
+
+        foo
+      RUBY
+
+      output = run_ruby_file do
+        type "'irb session'"
+        type "next"
+        type "'irb:debug session'"
+        type "step"
+        type "irb_info"
+        type "q!"
+      end
+
+      assert_include(output, "InputMethod: RelineInputMethod")
+
+      assert_equal <<~HISTORY, @history_file.open.read
+        'irb session'
+        next
+        'irb:debug session'
+        step
+        irb_info
+        q!
+      HISTORY
+    end
+
     def test_history_saving_with_nested_sessions
       write_history ""