Save history independently of the locale encoding

lib/irb/history.rb

@@ -76,7 +76,11 @@ def save_history
       begin
         ensure_history_file_permissions(history_file)
 
-        File.open(history_file, (append_history ? "a" : "w"), 0o600, encoding: IRB.conf[:LC_MESSAGES]&.encoding) do |f|
+        # Write the entries in the encoding they already carry. Forcing the
+        # locale's encoding raises Encoding::UndefinedConversionError on a
+        # non-ASCII entry under an ASCII locale, and the rescues below do not
+        # catch it, so IRB aborts on exit and the whole session is lost.
+        File.open(history_file, (append_history ? "a" : "w"), 0o600) do |f|
           hist = history.map { |l| l.scrub.split("\n").join("\\\n") }
 
           unless append_history || History.infinite?

test/irb/test_history.rb

@@ -163,6 +163,23 @@ def test_history_different_encodings
       INPUT
     end
 
+    def test_history_saves_non_ascii_input_under_an_ascii_locale
+      IRB.conf[:SAVE_HISTORY] = 2
+      IRB.conf[:LC_MESSAGES] = IRB::Locale.new("en_US.ASCII")
+      ENV["HOME"] = @tmpdir
+
+      io = TestInputMethodWithRelineHistory.new
+      io.class::HISTORY.clear
+      io.class::HISTORY << "puts 'h\u00e9llo'"
+
+      assert_nothing_raised do
+        io.save_history
+      end
+
+      assert_equal("puts 'h\u00e9llo'\n",
+                   File.read(IRB.rc_file("_history"), encoding: Encoding::UTF_8))
+    end
+
     def test_history_does_not_raise_when_history_file_directory_does_not_exist
       backup_history_file = IRB.conf[:HISTORY_FILE]
       IRB.conf[:SAVE_HISTORY] = 1