Debugging
Techniques and best practices for debugging plugins and handling errors in your language module development process.
Debugging JavaScript plugins that are embedded in C++ applications, such as Plugify, requires using the V8 Inspector to inspect and troubleshoot your JavaScript code. This guide provides an overview of how to debug JavaScript plugins in this context and directs you to external resources for detailed instructions.
Prerequisites
Before debugging your JavaScript plugins, ensure you have the following:
- V8 Engine (version 11.0 or later) installed and configured.
- Node.js (optional, for running the debugger).
- Plugify Core Library (built and available).
- V8 Language Module (`plugify-module-v8`) installed and configured.
- A JavaScript plugin to debug.
Debugging JavaScript Plugins with V8 Inspector
The V8 Inspector allows you to debug JavaScript code running in the V8 engine. Below are the general steps to debug JavaScript plugins embedded in C++ applications:
Enable V8 Inspector in Plugify
- Ensure the V8 Language Module is configured to enable the V8 Inspector.
- Launch Plugify with your JavaScript plugin loaded.
Connect to the V8 Inspector
- Open a browser (e.g., Chrome or Edge) and navigate to
chrome://inspect. - Under Devices, click Configure and add the address and port where the V8 Inspector is running (e.g.,
localhost:9229). - Your JavaScript plugin should appear under Remote Target. Click Inspect to open the DevTools.
Set Breakpoints
- Open the JavaScript source files for your plugin in the DevTools.
- Set breakpoints in your code by clicking in the left margin next to the line numbers.
Debug Your Plugin
- Trigger the functionality in your plugin that you want to debug.
- The debugger will pause execution at your breakpoints, allowing you to inspect variables, step through code, and analyze the call stack.
Detailed Debugging Guide
For a comprehensive step-by-step guide on using the V8 Inspector, refer to the official V8 documentation:
Common Debugging Scenarios
1. Plugin Crashes
- Check the Plugify logs for error messages.
- Use the V8 Inspector to identify the exact line of code causing the crash.
- Inspect variables and memory to diagnose the issue.
2. Plugin Not Loading
- Verify that the plugin is placed in the correct directory.
- Check for missing JavaScript dependencies or syntax errors.
- Use the V8 Inspector to step through the plugin initialization code.
3. Unexpected Behavior
- Set breakpoints in the relevant functions to trace the flow of execution.
- Inspect variable values to identify discrepancies.
- Use conditional breakpoints to debug specific scenarios.
Advanced Debugging Tips
1. Use Logging
- Add logging statements to your JavaScript plugin code to track execution flow and variable values.
- Use Plugify's built-in logging system to output messages to the console or log files.
2. Debugging Asynchronous Code
- Use the Async Call Stack feature in DevTools to trace asynchronous function calls.
- Inspect Promises and async/await functions to identify issues.
3. Debugging Memory Issues
- Use the Memory tab in DevTools to take heap snapshots and analyze memory usage.
- Identify memory leaks and optimize your plugin's memory consumption.
Troubleshooting
1. Debugger Not Connecting
- Ensure Plugify is running and the V8 Inspector is enabled.
- Verify that the correct address and port are configured in the browser.
2. Breakpoints Not Hit
- Ensure the JavaScript code matches the version being executed.
- Rebuild the plugin and restart Plugify.
3. Debugger Crashes
- Update V8 to the latest version.
- Ensure all dependencies are compatible with your development environment.
For more advanced debugging techniques and tools, refer to the V8 Documentation.