main: add a lockfile, and set the user data dir while debugging

See microsoft#127861 (comment)

.gitignore

@@ -16,3 +16,4 @@ test-results/
 yarn-error.log
 vscode.lsif
 vscode.db
+/.profile-oss

.vscode/launch.json

@@ -219,7 +219,7 @@
 			"cascadeTerminateToConfigurations": [
 				"Attach to Extension Host"
 			],
-			"userDataDir": false,
+			"userDataDir": "${workspaceFolder}/.profile-oss",
 			"pauseForSourceMap": false,
 			"outFiles": [
 				"${workspaceFolder}/out/**/*.js"

.vscode/settings.json

@@ -4,6 +4,7 @@
 	"files.exclude": {
 		".git": true,
 		".build": true,
+		".profile-oss": true,
 		"**/.DS_Store": true,
 		"build/**/*.js": {
 			"when": "$(basename).ts"

src/vs/code/electron-main/main.ts

@@ -59,6 +59,7 @@ import { cwd } from 'vs/base/common/process';
 import { IProtocolMainService } from 'vs/platform/protocol/electron-main/protocol';
 import { ProtocolMainService } from 'vs/platform/protocol/electron-main/protocolMainService';
 import { Promises } from 'vs/base/common/async';
+import { toDisposable } from 'vs/base/common/lifecycle';
 
 /**
  * The main VS Code entry point.
@@ -339,6 +340,9 @@ class CodeMain {
 			throw new ExpectedError('Sent env to running instance. Terminating...');
 		}
 
+		const lockFile = await this.createLockfile(environmentMainService);
+		once(lifecycleMainService.onWillShutdown)(() => lockFile.dispose());
+
 		// Print --status usage info
 		if (environmentMainService.args.status) {
 			logService.warn('Warning: The --status argument can only be used if Code is already running. Please run it again after Code has started.');
@@ -419,6 +423,18 @@ class CodeMain {
 		lifecycleMainService.kill(exitCode);
 	}
 
+	private async createLockfile(env: IEnvironmentMainService) {
+		await FSPromises.writeFile(env.mainLockfile, String(process.pid));
+
+		return toDisposable(() => {
+			try {
+				unlinkSync(env.mainLockfile);
+			} catch {
+				// ignored
+			}
+		});
+	}
+
 	//#region Command line arguments utilities
 
 	private resolveArgs(): NativeParsedArgs {

src/vs/platform/environment/electron-main/environmentMainService.ts

@@ -30,6 +30,7 @@ export interface IEnvironmentMainService extends INativeEnvironmentService {
 
 	// --- IPC
 	mainIPCHandle: string;
+	mainLockfile: string;
 
 	// --- config
 	sandbox: boolean;
@@ -52,6 +53,9 @@ export class EnvironmentMainService extends NativeEnvironmentService implements
 	@memoize
 	get mainIPCHandle(): string { return createStaticIPCHandle(this.userDataPath, 'main', this.productService.version); }
 
+	@memoize
+	get mainLockfile(): string { return join(this.userDataPath, 'code.lock'); }
+
 	@memoize
 	get sandbox(): boolean { return !!this.args['__sandbox']; }