Fix broken command history when executing debugger on irb

[takatea]

Related issue

#994

Enviroment

ruby -v: ruby 3.3.0preview1 (2023-05-12 master a1b01e7701) [x86_64-darwin22]
rdbg -v: rdbg 1.8.0

Description

This PR fixed the load_history method in the console.rb to handle the issue #994.

In particular, it contains the following changes:

• Load the history only if it doesn't exist
• Return value to the line count of the history

I have conducted the following test in addition to running all automatic tests (rake test_all) successfully in my local environment.

Additional test

The following steps are carried out to compare the output of .irb_history and .rdbg_history before and after the changes in this Pull Request.

1. Prepare a ruby script test.rb like this:

   require "debug"
   
   class Test
       def run
           debugger
       end
   end

2. Remove .irb_history and .rdbg_history to clean up

3. Run debugger without irb console. (e.g. ruby -e 'require "debug"; debugger')

4. Run the following commands on debugger console

   puts "only debugger 1"
   puts "only debugger 2"
   puts "only debugger 3"
   continue

5. Debugger and the ruby proess finished

6. Run irb

7. Run the following commands on irb

   require "./test"
   puts "irb 1"
   puts "irb 2"
   puts "irb 3"
   Test.new.run

8. Debugger started

9. Run the following commands on debugger console

   puts "debug 4"
   puts "debug 5"
   puts "debug 6"
   continue

10. Debugger finished (then I return to irb console)

11. Run quit to exit irb

(The same procedure is repeated as described above)

12. Run debugger again without irb console. (e.g. ruby -e 'require "debug"; debugger')

13. Run the following commands on debugger console

    puts "only debugger 4"
    puts "only debugger 5"
    puts "only debugger 6"
    continue

14. Debugger and the ruby proess finished

15. Run irb again

16. Run the following commands on irb

    require "./test"
    puts "irb 7"
    puts "irb 8"
    puts "irb 9"
    Test.new.run

17. Debugger started

18. Run the following commands on debugger console

    puts "debug 10"
    puts "debug 11"
    puts "debug 12"
    continue

19. Run quit to exit irb

And then, I got the following .irb_history and .rdbg_history files:

after revision

.irb_history

require "./test"
puts "irb 1"
puts "irb 2"
puts "irb 3"
Test.new.run
puts "debug 4"
puts "debug 5"
puts "debug 6"
continue
quit
require "./test"
puts "irb 7"
puts "irb 8"
puts "irb 9"
Test.new.run
puts "debug 10"
puts "debug 11"
puts "debug 12"
continue
quit

.rdbg_history

puts "only debugger 1"
puts "only debugger 2"
puts "only debugger 3"
continue
puts "debug 4"
puts "debug 5"
puts "debug 6"
continue
quit
puts "only debugger 4"
puts "only debugger 5"
puts "only debugger 6"
continue
puts "debug 10"
puts "debug 11"
puts "debug 12"
continue
quit

before revision

.irb_history

require "./test"
puts "irb 1"
puts "irb 2"
puts "irb 3"
Test.new.run
# Today's OMIKUJI: CHU-KICHI
puts "only debugger 1"
puts "only debugger 2"
puts "only debugger 3"
continue
puts "debug 4"
puts "debug 5"
puts "debug 6"
continue
quit
require "./test"
puts "irb 7"
puts "irb 8"
puts "irb 9"
Test.new.run
# Today's OMIKUJI: DAI-KICHI
puts "only debugger 1"
puts "only debugger 2"
puts "only debugger 3"
continue
puts "only debugger 1"
puts "only debugger 2"
puts "only debugger 3"
continue
puts "debug 4"
puts "debug 5"
puts "debug 6"
continue
quit
puts "only debugger 4"
puts "only debugger 5"
puts "only debugger 6"
continue
puts "debug 10"
puts "debug 11"
puts "debug 12"
continue
quit

.rdbg_history

puts "only debugger 1"
puts "only debugger 2"
puts "only debugger 3"
continue
puts "only debugger 1"
puts "only debugger 2"
puts "only debugger 3"
continue
puts "debug 4"
puts "debug 5"
puts "debug 6"
continue
quit
puts "only debugger 4"
puts "only debugger 5"
puts "only debugger 6"
continue
puts "irb 9"
Test.new.run
puts "only debugger 1"
puts "only debugger 2"
puts "only debugger 3"
continue
puts "only debugger 1"
puts "only debugger 2"
puts "only debugger 3"
continue
puts "debug 4"
puts "debug 5"
puts "debug 6"
continue
quit
puts "only debugger 4"
puts "only debugger 5"
puts "only debugger 6"
continue
puts "debug 10"
puts "debug 11"
puts "debug 12"
continue
quit