Reconnection when signal server is not active and minor changes

tools/launch-electron.js

@@ -1,5 +1,8 @@
 const { spawn } = require('child_process');
 
+const DEV_SINGLE_INSTANCE_EXIT_CODE = 23;
+const DEV_SINGLE_INSTANCE_EXIT_CODE_ENV = 'METOYOU_SINGLE_INSTANCE_EXIT_CODE';
+
 function isWaylandSession(env) {
   const sessionType = String(env.XDG_SESSION_TYPE || '').trim().toLowerCase();
 
@@ -44,11 +47,40 @@ function buildElectronArgs(argv) {
   return args;
 }
 
+function isDevelopmentLaunch(env) {
+  return String(env.NODE_ENV || '').trim().toLowerCase() === 'development';
+}
+
+function buildChildEnv(env) {
+  const nextEnv = { ...env };
+
+  if (isDevelopmentLaunch(env)) {
+    nextEnv[DEV_SINGLE_INSTANCE_EXIT_CODE_ENV] = String(DEV_SINGLE_INSTANCE_EXIT_CODE);
+  }
+
+  return nextEnv;
+}
+
+function keepProcessAliveForExistingInstance() {
+  console.log(
+    'Electron is already running; keeping the dev services alive and routing links to the open window.'
+  );
+
+  const intervalId = setInterval(() => {}, 60_000);
+  const shutdown = () => {
+    clearInterval(intervalId);
+    process.exit(0);
+  };
+
+  process.once('SIGINT', shutdown);
+  process.once('SIGTERM', shutdown);
+}
+
 function main() {
   const electronBinary = resolveElectronBinary();
   const args = buildElectronArgs(process.argv.slice(2));
   const child = spawn(electronBinary, args, {
-    env: process.env,
+    env: buildChildEnv(process.env),
     stdio: 'inherit'
   });
 
@@ -58,6 +90,11 @@ function main() {
   });
 
   child.on('exit', (code, signal) => {
+    if (code === DEV_SINGLE_INSTANCE_EXIT_CODE) {
+      keepProcessAliveForExistingInstance();
+      return;
+    }
+
     if (signal) {
       process.kill(process.pid, signal);
       return;