feat(desktop): self-update appimages in place (#2843)

fluxer_desktop/src/main/LinuxLaunchPath.ts

@@ -1,16 +1,57 @@
 // SPDX-License-Identifier: AGPL-3.0-or-later
 
-export function getStableLinuxLaunchPath(): string {
-	if (process.platform === 'linux') {
-		const appImage = process.env.APPIMAGE;
-		if (appImage && appImage.length > 0) return appImage;
-	}
-	return process.execPath;
+import {spawn} from 'node:child_process';
+import {existsSync} from 'node:fs';
+import {homedir} from 'node:os';
+import {createChildLogger} from '@electron/common/Logger';
+import {app} from 'electron';
+
+const logger = createChildLogger('LinuxLaunchPath');
+
+const PREFERRED_RELAUNCH_SHELL = '/bin/bash';
+const FALLBACK_RELAUNCH_SHELL = '/bin/sh';
+
+const RELAUNCH_AFTER_EXIT =
+	'pid="$1"; app="$2"; home="$3"; shift 3; cd /proc/self/fd && for n in *; do case "$n" in 0|1|2) ;; [0-9]) eval "exec $n>&-";; *) [ -n "$BASH_VERSION" ] && eval "exec $n>&-";; esac; done; cd "$home" || cd /; attempt=0; while [ "$attempt" -lt 300 ] && kill -0 "$pid"; do sleep 0.1; attempt=$((attempt + 1)); done; kill -0 "$pid" || exec "$app" "$@"';
+
+function getAppImagePath(): string | null {
+	if (process.platform !== 'linux') return null;
+	const appImage = process.env.APPIMAGE;
+	return appImage && appImage.length > 0 ? appImage : null;
 }
 
-export function getStableRelaunchOptions(): {execPath: string} | undefined {
-	if (process.platform !== 'linux') return undefined;
-	const execPath = getStableLinuxLaunchPath();
-	if (execPath === process.execPath) return undefined;
-	return {execPath};
+export function getStableLinuxLaunchPath(): string {
+	return getAppImagePath() ?? process.execPath;
+}
+
+export function relaunchStableLaunchPath(): void {
+	const appImagePath = getAppImagePath();
+	if (appImagePath == null) {
+		app.relaunch();
+		return;
+	}
+	try {
+		const child = spawn(
+			existsSync(PREFERRED_RELAUNCH_SHELL) ? PREFERRED_RELAUNCH_SHELL : FALLBACK_RELAUNCH_SHELL,
+			[
+				'-c',
+				RELAUNCH_AFTER_EXIT,
+				'fluxer-relaunch',
+				String(process.pid),
+				appImagePath,
+				homedir(),
+				...process.argv.slice(1),
+			],
+			{
+				cwd: homedir(),
+				detached: true,
+				stdio: 'ignore',
+			},
+		);
+		child.unref();
+		logger.info('Relaunching the AppImage once this process exits', {path: appImagePath, pid: child.pid});
+	} catch (error) {
+		logger.error('Failed to start the AppImage replacement process', {error});
+		app.relaunch({execPath: appImagePath});
+	}
 }