[ruby/irb] Handle handle_exception's exception

(https://github.com/ruby/irb/pull/780)

https://github.com/ruby/irb/commit/d42138c477

lib/irb.rb

@@ -743,7 +743,14 @@ module IRB
         message = message.gsub(/\(irb\):(?<num>\d+):in `<(?<frame>top \(required\))>'/)  { "(irb):#{$~[:num]}:in `<main>'" }
         puts message
       end
-      print "Maybe IRB bug!\n" if irb_bug
+      puts 'Maybe IRB bug!' if irb_bug
+    rescue Exception => handler_exc
+      begin
+        puts exc.inspect
+        puts "backtraces are hidden because #{handler_exc} was raised when processing them"
+      rescue Exception
+        puts 'Uninspectable exception occurred'
+      end
     end
 
     # Evaluates the given block using the given +path+ as the Context#irb_path

test/irb/test_raise_exception.rb

@@ -4,8 +4,8 @@ require "tmpdir"
 require_relative "helper"
 
 module TestIRB
-  class RaiseNoBacktraceExceptionTest < TestCase
-    def test_raise_exception
+  class RaiseExceptionTest < TestCase
+    def test_raise_exception_with_nil_backtrace
       bundle_exec = ENV.key?('BUNDLE_GEMFILE') ? ['-rbundler/setup'] : []
       assert_in_out_err(bundle_exec + %w[-rirb -W0 -e IRB.start(__FILE__) -- -f --], <<-IRB, /Exception: foo/, [])
       e = Exception.new("foo")
@@ -15,6 +15,27 @@ module TestIRB
 IRB
     end
 
+    def test_raise_exception_with_message_exception
+      bundle_exec = ENV.key?('BUNDLE_GEMFILE') ? ['-rbundler/setup'] : []
+      expected = /#<Exception: foo>\nbacktraces are hidden because bar was raised when processing them/
+      assert_in_out_err(bundle_exec + %w[-rirb -W0 -e IRB.start(__FILE__) -- -f --], <<-IRB, expected, [])
+      e = Exception.new("foo")
+      def e.message; raise 'bar'; end
+      raise e
+IRB
+    end
+
+    def test_raise_exception_with_message_inspect_exception
+      bundle_exec = ENV.key?('BUNDLE_GEMFILE') ? ['-rbundler/setup'] : []
+      expected = /Uninspectable exception occurred/
+      assert_in_out_err(bundle_exec + %w[-rirb -W0 -e IRB.start(__FILE__) -- -f --], <<-IRB, expected, [])
+      e = Exception.new("foo")
+      def e.message; raise; end
+      def e.inspect; raise; end
+      raise e
+IRB
+    end
+
     def test_raise_exception_with_invalid_byte_sequence
       pend if RUBY_ENGINE == 'truffleruby' || /mswin|mingw/ =~ RUBY_PLATFORM
       bundle_exec = ENV.key?('BUNDLE_GEMFILE') ? ['-rbundler/setup'] : []