Kill any processes started by coapp on exit

app/src/converter.js

@@ -2,7 +2,6 @@ import open from 'open';
 
 const os = require("os");
 const path = require('path');
-const { spawn } = require('child_process');
 
 const logger = require('./logger');
 const rpc = require('./weh-rpc');
@@ -16,6 +15,27 @@ if (os.platform() == "win32") {
   ffprobe += ".exe";
 }
 
+// Record all started processes, and kill them if the coapp
+// ends, crash or is killed by the browser.
+let to_kill = new Set();
+function spawn(arg0, argv) {
+  const { spawn } = require('child_process');
+  let process = spawn(arg0, argv);
+  if (process.pid) {
+    to_kill.add(process);
+    process.on("exit", () => to_kill.delete(process));
+  }
+  return process;
+}
+for (let e of ["exit", "SIGINT", "SIGTERM", "uncaughtException"]) {
+  process.on(e, () => {
+    for (let process of to_kill) {
+      try { process.kill(9); } catch (_) { /* */ }
+    }
+    process.exit(0);
+  });
+}
+
 function ExecConverter(args) {
   return new Promise((resolve, reject) => {
     let convProcess = spawn(ffmpeg, args);