JCEF Bug Reproduction Plugin

This IntelliJ IDEA plugin is designed to reproduce a bug related to JCEF (Java Chromium Embedded Framework) WebView and CefMessageRouter.

What This Plugin Does

The plugin creates:

1. Tool Window: A "JCEF Bug" tool window on the right side with a button to open the dialog
2. Menu Action: An action in the Tools menu and main toolbar to open the dialog
3. Dialog with JCEF: A dialog window that contains:
   • A JPanel as content holder
   • A JCEFWebView (JBCefBrowser)
   • A registered CefMessageRouter for JavaScript ↔ Java communication
   • Test HTML page with JavaScript that sends messages to Java

How to Reproduce the Bug

Manual Testing

1. Build and Run: Build the plugin and run it in a development instance of IntelliJ IDEA
2. Open Dialog: Use either:
   • The "JCEF Bug" tool window button (right side panel)
   • Tools menu → "Open JCEF Dialog"
   • Main toolbar button
3. Trigger Bug: Click OK/Cancel buttons as fast as possible to rapidly open/close dialogs
4. Monitor Console: Watch for error messages and stack traces

Automated Testing (Recommended)

The plugin includes automated stress testing to systematically reproduce the bug:

1. Simple Fast Stress Test

• Access: Tools menu → "Simple Fast Stress Test" OR tool window "Simple Fast Test" button
• Features:
  • Configurable number of iterations (default: 1000)
  • Configurable delay between iterations (default: 10ms)
  • Simple open → wait → close cycle
  • Stops immediately on any error
• Use Case: Automated rapid dialog cycling to trigger race conditions

2. Aggressive Test (Most Effective)

• Access: Tools menu → "Start Aggressive JCEF Test"
• Features:
  • Multiple concurrent testing strategies:
    • Rapid sequential: Very fast open/close cycles (5ms delay)
    • Overlapping lifecycles: Random timing between open/close (10-60ms)
    • Immediate close: Manual close immediately after show (race condition)
  • Multi-threaded execution to trigger race conditions
  • Real-time monitoring of active dialogs and errors
  • Auto-stops after 10 errors or 5 minutes
• Use Case: Maximum pressure testing with concurrent dialog lifecycles

Technical Details

Components Created

• JCEFBugAction: Action class that opens the dialog
• JCEFBugDialog: Modal DialogWrapper containing the JCEF WebView with manual OK/Cancel buttons
• JCEFBugSimpleStressTest: Simple automated stress testing with configurable parameters
• JCEFBugAggressiveTest: Multi-threaded concurrent testing for maximum race condition pressure
• JCEFBugTargetedTest: Isolates the CefMessageRouter creation race condition
• JCEFBugToolWindow: Tool window factory and content
• CefMessageRouter: Configured with test communication handlers

JCEF Setup

The dialog creates:

• JBCefBrowser instance
• CefMessageRouter with "jcefQuery" and "jcefQueryCancel"
• Message handler that echoes received messages
• Test HTML with JavaScript that sends messages via window.jcefQuery()

Test Communication

The HTML page includes:

• Buttons to send test messages
• JavaScript that communicates with Java via CefMessageRouter
• Output area showing communication results
• Automatic message sending on page load

Building and Running

# Build the plugin
./gradlew buildPlugin

# Run in development IDE
./gradlew runIde

Expected Behavior for Bug Reproduction

When opening and closing the dialog rapidly multiple times, the CefMessageRouter and JCEF WebView disposal/cleanup should eventually trigger the bug you're investigating. The combination of:

• Quick dialog open/close cycles
• Active JavaScript ↔ Java communication
• CefMessageRouter cleanup during disposal

Should create the conditions needed to reproduce the issue.

🐛 Confirmed Bug Reproduction

Bug: java.lang.NullPointerException: Cannot read field "objId" because "robj" is null

Location: com.jetbrains.cef.remote.router.RemoteMessageRouterImpl.create(RemoteMessageRouterImpl.java:38)

Root Cause: Race condition in JCEF's remote message router initialization where the remote object (robj) is accessed before being properly initialized.

Trigger Conditions:

• Rapid CefMessageRouter creation/disposal cycles
• Multiple concurrent JCEF browser instances
• Remote CEF server connection timing issues

Reproduction Success: ✅ Confirmed with the stress testing tools in this plugin.

Complete Tools Menu

All available actions in Tools menu:

1. Open JCEF Bug Dialog - Basic manual dialog for rapid clicking
2. Simple Fast Stress Test - Automated stress testing with configurable parameters
3. Start Aggressive JCEF Test - Multi-threaded concurrent testing (most effective)
4. Manual Test Dialog - Single dialog for manual verification
5. Targeted RemoteMessageRouter Race Test - Isolates CefMessageRouter creation race
6. Test Dialog Close Mechanism - Tests basic dialog closing functionality