[debug]: Debug session might be configured with an empty capabilities object

[kittaakos]

Bug Description:

There could be a race condition when starting a debug session. I can consistently reproduce the issue with the debugger from the vscode.mock-debug VS Code extension. You can also use this: https://github.com/kittaakos/vscode-mock-debug/raw/theia/mock-debug-0.51.0.vsix

Problem:

1. Capabilities is initialized as an empty object:
   

   theia/packages/debug/src/browser/debug-session.tsx

   Lines 130 to 133 in fe8e4c1

   	protected _capabilities: DebugProtocol.Capabilities = {};
   	get capabilities(): DebugProtocol.Capabilities {
   	return this._capabilities;
   	}

2. Theia sends the 'initialize' request here to get the debugger capabilities:
   

   theia/packages/debug/src/browser/debug-session.tsx

   Line 275 in fe8e4c1

   const response = await this.connection.sendRequest('initialize', {

3. But the initialized event is received before the sendRequest('initialize') resolves:
   

   theia/packages/debug/src/browser/debug-session.tsx

   Line 112 in fe8e4c1

   this.connection.on('initialized', () => this.configure()),

4. Theia starts the debug session configuration (e.g., exception breakpoint filters) with the empty, uninitialized capabilities object:
   

   theia/packages/debug/src/browser/debug-session.tsx

   Lines 307 to 318 in fe8e4c1

   	if (this.capabilities.exceptionBreakpointFilters) {
   	const exceptionBreakpoints = [];
   	for (const filter of this.capabilities.exceptionBreakpointFilters) {
   	const origin = this.breakpoints.getExceptionBreakpoint(filter.filter);
   	exceptionBreakpoints.push(ExceptionBreakpoint.create(filter, origin));
   	}
   	this.breakpoints.setExceptionBreakpoints(exceptionBreakpoints);
   	}
   	await this.updateBreakpoints({ sourceModified: false });
   	if (this.capabilities.supportsConfigurationDoneRequest) {
   	await this.sendRequest('configurationDone', {});
   	}

5. Once the debug session is configured, the capabilities are set:
   

   theia/packages/debug/src/browser/debug-session.tsx

   Line 287 in fe8e4c1

   this.updateCapabilities(response?.body || {});

I can confirm I cannot reproduce the same with the Node.js debugger in Theia (from the sources).

Steps to Reproduce:

Additional Information

• Operating System: macOS 12.5.1
• Theia Version: fe8e4c1

[kittaakos]

I can consistently reproduce the issue with the debugger from the vscode.mock-debug

I cannot reproduce the same with the Node.js debugger in Theia

From mock-debug:

// since this debug adapter can accept configuration requests like 'setBreakpoint' at any time,
// we request them early by sending an 'initializeRequest' to the frontend.
// The frontend will end the configuration sequence by calling 'configurationDone' request.

[kittaakos]

I will take care of this issue.