VSCode Ruby rdbg Debugger

Ruby debugger to connect debug library which utilize recent Ruby's debug support features.

Requirement

You need to install latest debug gem and rdbg command should be in $PATH.

$ gem install debug

How to use

Launch without configuration

Without any configuration, you can use this debugger by "Start Debugging" (F5 key) if you activate .rb file.

You will see the "Debug command line" input dialog. Please specify your favorite command line you want to debug.

For example:

• ruby foo.rb (launch foo.rb)
• ruby foo.rb 10 20 30 (launch foo.rb with options 10, 20 and 30)
• rake taskA (launch rake task taskA)
• bundle exec rspec (launch rspec command with bundle exec)
• bin/rails s (launch bin/rails s)

When you select a command line, the specified command will run on rdbg debugger, and VSCode will connect to the rdbg debugger with UNIX domain socket.

And new terminal is created (named rdbg). You can see stdout/err outputs and you can input stdin on rdbg terminal.

You can stop the programs

• by setting breakpoints (F9) on source code.
• by exception (if you enable "rescue exception").
• by pushing the Pause button (F6).

When the program stops, you can see "Call stack", "Variables" and you can set "Watch" expressions. On the debug console, you can input valid Ruby program and you will get an evaluation result on selected context ("Call stack").

See also: Debugging in Visual Studio Code

For developers: RUBY_DEBUG_DAP_SHOW_PROTOCOL=1 on rdbg terminal will show the all DAP protocol.

Launch with configurations

You can write your favorite setting in .vscode/launch.json.

To make a .vscode/launch.json with default settings, you only need to click "create a launch.json file" on the "Run and Debug" pane. And you will see the following default configurations.

{
        // Use IntelliSense to learn about possible attributes.
        // Hover to view descriptions of existing attributes.
        // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
        "version": "0.2.0",
        "configurations": [
                {
                        "type": "rdbg",
                        "name": "Debug current file with rdbg",
                        "request": "launch",
                        "script": "${file}",
                        "args": [],
                        "askParameters": true
                },
                {
                        "type": "rdbg",
                        "name": "Attach with rdbg",
                        "request": "attach"
                }
        ]
}

It contains "Debug current file with rdbg" (launch) configuration and "Attach with rdbg" (attach) configuration. You can modify this configuration, and also you can add your favorite configuration like:

                {
                        "type": "rdbg",
                        "name": "Run rake test",
                        "request": "launch",
                        "command": "rake",
                        "script": "test", // launch rake test with debugger
                        "args": [],
                        "askParameters": false // Do not ask startup parameter any more
                },

You can use the following "launch" configurations.

• script: Script file name (default: active ruby file on VSCode)
• command: Executable command (default: ruby)
• cwd: Directory to execute the program in (default: ${workspaceFolder})
• args: Command line arguments passed to the program (default: [])
• env: Additional environment variables to pass to the debugging (and debugged) process.
• useBundler: Execute Ruby programs with bundle exec if command configuration is not given and Gemfile is available in the workspace.
• askParameters: Ask "Debug command line" before debugging (default: true)
• rdbgPath: Location of the rdbg executable (default: rdbg).
• debugPort: On default (without debugPort configulation), open a UNIX Domain Socket with default name to communicate with debuggee. If you want to use another debug port, set this configuration.
  • 12345: open a TCP/IP debug port with port 12345
  • hostname:12345: open a TCP/IP port 12345 and hostname hostname
  • Otherwize, open a UNIX Domain socket with given filename.
  • Note that you can specify 0 TCP/IP port (choose usable port) with debug.gem v1.5.0 or later.
• waitLaunchTime: If you want to open TCP/IP debug port, you may need to wait for opening debug port. On default, it waits 1000 milli seconds (1 sec) but if it is not enough, please specify more wait time (default: 1000 in milli seconds). With debug.gem 1.5.0 and later you may not need this configulation.
• localfs: On TCP/IP, if target host is local machine, set true and you can open the file directly (default: false).

Note that if you have a trouble by launching rdbg, please try to specify rdbgPath. Without this configuration, this extension simply calls rdbg in PATH.

Attach to the running Ruby process

You can attach to a Ruby process which run with an opening debugger port.

The following command starts the foo.rb with opening debug port. There are more methods to open the port. See more for ruby/debug: Debugging functionality for Ruby.

$ rdbg --open foo.rb

After that, you can connect to the debug port. This extension searches opening debugger port and attach to that port by running Attach with rdbg (select it on the top of "RUN AND DEBUG" pane and push the green "Start Debugging" button).

You can specify the following "attach" configurations.

• rdbgPath: Same as launch request.
• debugPort: Same as launch request.
• localfs: Same as launch request.
• localfsMap: Specify pairs of remote root path and local root path like /remote_dir:/local_dir. You can specify multiple pairs like /rem1:/loc1,/rem2:/loc2 by concatenating with ,.

With debugPort, you can attach to TCP/IP debug port.

• Start with a TCP/IP debug port with rdbg --open --port 12345 foo.rb
• Add debugPort: '12345' attach configration.
• Choose Attach with rdbg and start attach debugging

localfsMap is helpful if you run the debuggee and share the same file system with another name in debuggee.

For example, running a docker container with -v option (and --network=host to communicate with the host and a docker container) option like that:

$ docker run --network=host -it -v `pwd`:/app/ --rm ruby bash
/:# cd app
/app:# rdbg -O --port=12345 target.rb

In this case, the current directory of host (${workspaceFolder}) is shared with the name /app in a container and VSCode on the host can connect to the debuggee process in a container by TCP/IP port 12345. The launch.json configuration should be:

        {
            "type": "rdbg",
            "name": "Attach with rdbg (tcp 12345)", // Specify your favorite name
            "request": "attach",
            "debugPort": "localhost:12345",
            "localfsMap": "/app:${workspaceFolder}"
        }

Acknowledgement

This extension is based on Ethan Reesor / VSCode Byebug · GitLab by Ethan Reesor. Without his great work, the extension can not be released (Koichi learned TypeScript, VSCode extension and DAP by his extension).