Debugging AngelScript in Rider

January 1, 2026 · View on GitHub

This guide explains how to set up and use debugging for AngelScript code in your Unreal Engine project.

Features

  • ✅ Breakpoints - Set breakpoints by clicking in the gutter
  • ✅ Step Debugging - Step over, into, and out of functions
  • ✅ Variable Inspection - Inspect locals, globals, and member variables
  • ✅ Debug Inline Values - See variable values displayed inline during debugging
  • ✅ Call Stack - Navigate the execution stack
  • ✅ Exception Breakpoints - Break on assertions, errors, or warnings
  • ✅ Expression Evaluation - Evaluate AngelScript expressions while paused
  • ❌ Data Breakpoints - Not supported (LSP4IJ framework limitation - missing DataBreakpointInfo/SetDataBreakpoints requests)

Prerequisites

  1. Node.js installed on your system (any recent version)
  2. Unreal Engine with the AngelScript plugin running
  3. Your project's Script folder opened in Rider

Setup Debugging

Step 1: Create a Debug Configuration

  1. Go to Run → Edit Configurations (or click the dropdown next to the Run button)
  2. Click the + button and select Debug Adapter Protocol
  3. Give it a name like "Debug AngelScript"

Step 2: Configure the Debug Adapter

  1. In the configuration dialog, locate the Server dropdown
  2. Select AngelScript Debug Adapter from the list
    • If you don't see this option, make sure the plugin is installed and Rider has been restarted

Step 3: Save the Configuration

Click OK to save your debug configuration.

Using the Debugger

Note: Keys may differ based on IDE configuration.

Setting Breakpoints

  1. Open any .as file in your project
  2. Click in the gutter (left margin) next to a line of code
  3. A red dot should appear indicating a breakpoint

Starting a Debug Session

  1. Make sure Unreal Engine is running with your project loaded
  2. Select your debug configuration from the dropdown (top-right)
  3. Click the Debug button (or press Shift+F9)

    Note: Clicking the Run button will appear to connect the debugger, but debugging in this state will not work.

  4. The debugger will connect to Unreal Engine

When a Breakpoint Hits

When your code reaches a breakpoint:

  • ⏸️ Execution pauses in both Unreal Engine and Rider
  • 📊 Variables panel shows local variables, this, and globals
  • 📚 Call Stack panel shows the execution stack
  • 🎮 Debug toolbar allows you to step through code

Stepping Through Code

  • F8 - Step Over (execute current line, don't enter functions)
  • F7 - Step Into (enter function calls)
  • Shift+F8 - Step Out (finish current function and return to caller)
  • F9 - Resume execution (continue until next breakpoint)

Inspecting Variables

  • Hover over any variable to see its value
  • Expand objects in the Variables panel to see members
  • Right-click variables for more options (Add to Watches, etc.)

Evaluating Expressions

  • Use the Evaluate Expression dialog (Alt+F8) to execute AngelScript code
  • Type any expression and see the result
  • You can call functions, access properties, etc.

Advanced Features

Concurrent Debugging (C++ + AngelScript)

You can debug C++ and AngelScript simultaneously:

  1. Attach Rider's C++ debugger to the Unreal Editor process
  2. Start an AngelScript debug session (as described above)
  3. Both debuggers work independently:
    • C++ debugger controls the native process
    • AngelScript debugger communicates with the script VM via TCP

This allows you to:

  • Set breakpoints in both C++ and AngelScript code
  • Step from C++ into AngelScript and vice versa
  • See the full execution flow across native and script code

Troubleshooting

"Node.js executable not found"

Problem: Debug adapter can't start

Solution: Install Node.js from https://nodejs.org/ or ensure it's in your PATH

"Connection refused" or Timeout

Problem: Can't connect to Unreal Engine

Solutions:

  1. Make sure Unreal Engine is running with your project loaded
  2. Verify the port is 27099 (default) or check your project settings
  3. Check if a firewall is blocking the connection
  4. Verify the AngelScript plugin is enabled in Unreal

Breakpoints Not Hitting

Problem: Breakpoints are set but execution doesn't stop

Solutions:

  1. Make sure the debug session is active (green indicator in toolbar)
  2. Verify the code is actually being executed (add a log statement)
  3. Check that the file path matches between Rider and Unreal
  4. Set Working Directory to your Unreal project root

Variables Show as "Unavailable"

Problem: Can't inspect variable values

Solutions:

  1. Make sure you're paused at a breakpoint (not just stopped)
  2. Try stepping to the next line
  3. Some variables might be optimized away by the AngelScript compiler

Configuration Options

Custom Port

The debug port is configurable in the plugin settings:

  1. Go to Settings → Languages & Frameworks → AngelScript → General
  2. Change Unreal Connection Port (default: 27099)
  3. Restart your debug session for changes to take effect

Note: The port must match the debug server port configured in your Unreal Engine project.

Multiple Unreal Instances

To debug multiple Unreal instances simultaneously:

  1. Configure each Unreal instance to use a different debug port
  2. In Rider settings, set the port to match your target instance
  3. Each debug session will connect to the port specified in settings

Known Limitations

  1. No hot reload: Changing code during debugging requires restarting the session
  2. Data breakpoints: Not supported due to LSP4IJ framework limitations (missing DAP protocol support)
  3. Conditional breakpoints: Not yet supported (standard DAP feature, may be added in future LSP4IJ updates)

Additional Resources

Support

If you encounter issues:

  1. Check the Event Log in Rider (View → Tool Windows → Event Log)
  2. Enable verbose logging for the debug adapter (edit configuration → trace: true)
  3. Report issues at: https://github.com/scriptacus/rider-unreal-angelscript/issues