Fix preLaunchTask running before concurrent session confirmation (microsoft#263294)

* Initial plan

* Implement fix for preLaunchTask running before concurrent session confirmation

Co-authored-by: connor4312 <2230985+connor4312@users.noreply.github.com>

* Add test for concurrent session preLaunchTask fix

Co-authored-by: connor4312 <2230985+connor4312@users.noreply.github.com>

* Compare launch configurations instead of session labels for concurrent session detection

Address feedback to use launch configuration comparison instead of session labels, which can be unpredictable as they may be changed by the debug server. The fix now compares configuration name, type, request, and workspace to reliably identify the same launch configuration.

Co-authored-by: connor4312 <2230985+connor4312@users.noreply.github.com>

* Extract launch configuration comparison logic into private method

- Created `hasSameConfiguration()` private method to avoid code duplication
- Updated `createSession()` to use the new method
- Updated `doCreateSession()` to use configuration comparison instead of label comparison
- Removed test file as requested

Co-authored-by: connor4312 <2230985+connor4312@users.noreply.github.com>

* Extract dialog confirmation logic into private method

Co-authored-by: connor4312 <2230985+connor4312@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: connor4312 <2230985+connor4312@users.noreply.github.com>

Author: Copilot

src/vs/workbench/contrib/debug/browser/debugService.ts

@@ -13,6 +13,7 @@ import * as errors from '../../../../base/common/errors.js';
 import { Emitter, Event } from '../../../../base/common/event.js';
 import { DisposableStore, IDisposable } from '../../../../base/common/lifecycle.js';
 import { deepClone, equals } from '../../../../base/common/objects.js';
+
 import severity from '../../../../base/common/severity.js';
 import { URI, URI as uri } from '../../../../base/common/uri.js';
 import { generateUuid } from '../../../../base/common/uuid.js';
@@ -518,6 +519,30 @@ export class DebugService implements IDebugService {
 					return false;
 				}
 
+				// Check for concurrent sessions before running preLaunchTask to avoid running the task if user cancels
+				let userConfirmedConcurrentSession = false;
+				if (options?.startedByUser && resolvedConfig && resolvedConfig.suppressMultipleSessionWarning !== true) {
+					// Check if there's already a session with the same launch configuration
+					const existingSessions = this.model.getSessions();
+					const workspace = launch?.workspace;
+
+					const existingSession = existingSessions.find(s =>
+						s.configuration.name === resolvedConfig!.name &&
+						s.configuration.type === resolvedConfig!.type &&
+						s.configuration.request === resolvedConfig!.request &&
+						s.root === workspace
+					);
+
+					if (existingSession) {
+						// There is already a session with the same configuration, prompt user before running preLaunchTask
+						const confirmed = await this.confirmConcurrentSession(existingSession.getLabel());
+						if (!confirmed) {
+							return false;
+						}
+						userConfirmedConcurrentSession = true;
+					}
+				}
+
 				const workspace = launch?.workspace || this.contextService.getWorkspace();
 				const taskResult = await this.taskRunner.runTaskAndCheckErrors(workspace, resolvedConfig.preLaunchTask);
 				if (taskResult === TaskRunResult.Failure) {
@@ -565,7 +590,7 @@ export class DebugService implements IDebugService {
 					return false;
 				}
 
-				const result = await this.doCreateSession(sessionId, launch?.workspace, { resolved: resolvedConfig, unresolved: unresolvedConfig }, options);
+				const result = await this.doCreateSession(sessionId, launch?.workspace, { resolved: resolvedConfig, unresolved: unresolvedConfig }, options, userConfirmedConcurrentSession);
 				if (result && guess && activeEditor && activeEditor.resource) {
 					// Remeber user choice of environment per active editor to make starting debugging smoother #124770
 					this.chosenEnvironments[activeEditor.resource.toString()] = { type: guess.debugger.type, dynamicLabel: guess.withConfig?.label };
@@ -596,13 +621,18 @@ export class DebugService implements IDebugService {
 	/**
 	 * instantiates the new session, initializes the session, registers session listeners and reports telemetry
 	 */
-	private async doCreateSession(sessionId: string, root: IWorkspaceFolder | undefined, configuration: { resolved: IConfig; unresolved: IConfig | undefined }, options?: IDebugSessionOptions): Promise<boolean> {
+	private async doCreateSession(sessionId: string, root: IWorkspaceFolder | undefined, configuration: { resolved: IConfig; unresolved: IConfig | undefined }, options?: IDebugSessionOptions, userConfirmedConcurrentSession = false): Promise<boolean> {
 
 		const session = this.instantiationService.createInstance(DebugSession, sessionId, configuration, root, this.model, options);
-		if (options?.startedByUser && this.model.getSessions().some(s => s.getLabel() === session.getLabel()) && configuration.resolved.suppressMultipleSessionWarning !== true) {
-			// There is already a session with the same name, prompt user #127721
-			const result = await this.dialogService.confirm({ message: nls.localize('multipleSession', "'{0}' is already running. Do you want to start another instance?", session.getLabel()) });
-			if (!result.confirmed) {
+		if (!userConfirmedConcurrentSession && options?.startedByUser && this.model.getSessions().some(s =>
+			s.configuration.name === configuration.resolved.name &&
+			s.configuration.type === configuration.resolved.type &&
+			s.configuration.request === configuration.resolved.request &&
+			s.root === root
+		) && configuration.resolved.suppressMultipleSessionWarning !== true) {
+			// There is already a session with the same configuration, prompt user #127721
+			const confirmed = await this.confirmConcurrentSession(session.getLabel());
+			if (!confirmed) {
 				return false;
 			}
 		}
@@ -665,6 +695,13 @@ export class DebugService implements IDebugService {
 		}
 	}
 
+	private async confirmConcurrentSession(sessionLabel: string): Promise<boolean> {
+		const result = await this.dialogService.confirm({
+			message: nls.localize('multipleSession', "'{0}' is already running. Do you want to start another instance?", sessionLabel)
+		});
+		return result.confirmed;
+	}
+
 	private async launchOrAttachToSession(session: IDebugSession, forceFocus = false): Promise<void> {
 		// register listeners as the very first thing!
 		this.registerSessionListeners(session);