Install the VS Code Ruby extension and the debug gem via gem install debug or add it to your Gemfile. 2. Create a launch.json file in VS Code under the Run and Debug view, then configure it for your use case—use "program": "${workspaceFolder}/app.rb" for scripts or set "program": "${workspaceFolder}/bin/rails" with args: ["server"] for Rails. 3. Set breakpoints by clicking the left margin in the editor. 4. Select the debug configuration and start debugging with F5, allowing inspection of variables, code stepping, and expression evaluation in the Debug Console. 5. Use binding.break in code for temporary breakpoints and ensure the correct Ruby version is active in VS Code when using rbenv, rvm, or chruby, with all relevant output checked in the integrated terminal or Debug Console, making debugging reliable for Ruby scripts, Rails applications, and RSpec tests.

Debugging a Ruby application in VS Code is straightforward once you set up the right tools. Here’s how to do it effectively.

Install the Required Extensions and Gems

First, make sure you have the necessary components:

• VS Code Ruby extension: Install the official Ruby extension by Peng Lv. It provides basic syntax support and integrates with debugging tools.
• Debug gem: The modern way to debug Ruby in VS Code uses the debug gem (formerly debase with ruby-debug-ide is outdated).

Run this command to install the debug gem:

gem install debug

Or, if you're using Bundler, add it to your Gemfile:

gem 'debug', require: 'debug/proxy'

Then run:

bundle install

Configure launch.json for Debugging

In VS Code, go to the Run and Debug view (Ctrl Shift D), then click "create a launch.json file" if you don’t have one.

Choose Ruby as the environment, and VS Code will generate a default launch.json. Modify it depending on your use case.

Basic Configuration for a Ruby Script

If you're debugging a simple Ruby file (e.g., app.rb):

{
  "version": "0.2.0",
  "configurations": [
    {
      "name": "Debug Ruby File",
      "type": "Ruby",
      "request": "launch",
      "program": "${workspaceFolder}/app.rb"
    }
  ]
}

Debugging a Rails Application

For Rails, you’ll want to start the server in debug mode:

{
  "version": "0.2.0",
  "configurations": [
    {
      "name": "Debug Rails Server",
      "type": "Ruby",
      "request": "launch",
      "program": "${workspaceFolder}/bin/rails",
      "args": [
        "server"
      ]
    },
    {
      "name": "Debug RSpec",
      "type": "Ruby",
      "request": "launch",
      "program": "${workspaceFolder}/bin/rspec",
      "args": [
        "--require", "debug",
        "--debug",
        "${relativeFile}"
      ],
      "console": "integratedTerminal"
    }
  ]
}

Note: Using --debug and --require debug ensures the debug gem is loaded properly.

Set Breakpoints and Start Debugging

1. Open the Ruby file you want to debug.
2. Click the left margin (next to the line numbers) to set a breakpoint (a red dot will appear).
3. Go to the Run and Debug sidebar, select the configuration (e.g., "Debug Ruby File"), and click Start Debugging (F5).
4. The program will pause at your breakpoint. You can now:
   • Inspect variables in the sidebar
   • Step over, into, or out of code (using toolbar or F10/F11)
   • Use the Debug Console to evaluate expressions

Tips for Smoother Debugging

• Use binding.break for temporary breakpoints in code: You can insert binding.break directly in your Ruby code as a one-off breakpoint. When the debugger runs, it will pause there automatically.
• Ensure correct Ruby environment: If you're using rbenv, rvm, or chruby, make sure VS Code is using the right Ruby version. You can set the Ruby path in settings if needed.
• Check output in the Debug Console or Terminal: Some debug output may appear in the integrated terminal, especially for Rails or RSpec.

Basically, it comes down to installing the debug gem, setting up launch.json, and using breakpoints. Once configured, debugging Ruby in VS Code works reliably for scripts, Rails, and tests.

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