ruby-rdbg.md

Ruby (rdbg) DAP server

To debug Ruby files, you can use the Ruby rdbg DAP server.

Let’s debug the following hello.rb file:

def main
  user = "hello world"
  puts user
end

if __FILE__ == $0
  main
end

Configure DAP server

1. install Ruby. After that open a terminal and type ruby -v to check Ruby is installed correctly.

2. Use gem install debug to install the required debug gem.

3. Create a test file named hello.rb with a simple Ruby script that includes a main() function printing "hello world"

def main
  user = "hello world"
  puts user
end

if __FILE__ == $0
  main
end

4. Create a DAP Run/Debug configuration:

   

5. In the Server tab, click on create a new server:

   

6. It opens a new dialog to create DAP server, select Python- Debugpy template:

7. After clicking on OK button, it will select the new server and pre-fill configurations:

As Ruby rdbg DAP server is consumed with attach request, the command is empty.

8. Enable DAP server traces

If you wish to show DAP request/response traces when you will debug:

you need to select Trace with verbose.

Configure file mappings

To allows settings breakpoints to Python files, you need configure mappings in the Mappings tab. As you have selected Python- Debugpy server, it will automatically populate the file mappings like this:

Configure the Ruby file to run/debug with attach

As you have selected Python- Debugpy server, it will automatically populate the Attach configuration like this:

1. Attach as Debug mode should be selected.
2. The DAP parameters of the launch should look like this:

{
   "name": "Attach with rdbg",
   "type": "rdbg",
   "request": "attach",
   "redirectOutput": true,
   "connect": {
      "host": "127.0.0.1",
      "port": 12345
   }
}

Address input is pre-filled with $connect.host and Port input is pre-filled with $connect.port which means that JSON configuration is used to retrieve the address and the port. You can see on the right of the inputs the real value of the address and port:

If you don't want to use JSON configuration, you can fill directly the real value:

The pre-filled configuration uses "redirectOutput": true to show output (like print(....)) in the IntelliJ console. Read Python debugging in VS Code for more information.

Set Breakpoint

After applying the run configuration, you should set a breakpoint to files which matches file mappings. Set a breakpoint in the test.py file:

Start Ruby program in a Terminal

Open an IntelliJ Terminal (or other terminal), navigate to the directory containing your test file and execute the following command to start the debug server:

rdbg --open --port 12345 hello.rb

This will make the script wait for a debugger to attach.

Debugging

Before starting the configuration, check that your address and port are correct:

You can start the run configuration in either Run or Debug mode. Once started, you should see DAP traces in the console:

You will also see Threads and Variables:

As Debugpy can support completion, you should benefit it: