forward signals correctly

signals are passed to the spawned child process; this means
that the main process should not react to them, and instead
wait for the spawned process to exit as a result of receiving
the forwarded signal.

Author: stelcheck

src/bin.ts

@@ -54,16 +54,43 @@ v8flags(function (err, v8flags) {
   const proc = spawn(
     process.execPath,
     nodeArgs.concat(join(__dirname, '_bin.js'), scriptArgs),
-    { stdio: 'inherit' }
+    {
+      // We need to run in detached mode so to avoid
+      // automatic propagation of signals to the child process.
+      // This is necessary because by default, keyboard interrupts
+      // are propagated to the process tree, but `kill` is not.
+      //
+      // See: https://nodejs.org/api/child_process.html#child_process_options_detached
+      detached: true,
+
+      // Pipe all input and output to this process
+      stdio: 'inherit'
+    }
   )
 
-  proc.on('exit', function (code: number, signal: string) {
-    process.on('exit', function () {
-      if (signal) {
-        process.kill(process.pid, signal)
-      } else {
-        process.exit(code)
-      }
-    })
+  // Ignore signals, and instead forward them to the
+  // child process
+  const forward = (signal: string) => process.on(signal, () => proc.kill(signal))
+
+  // Interrupt (CTRL-C)
+  forward('SIGINT')
+
+  // Termination (`kill` default signal)
+  forward('SIGTERM')
+
+  // Terminal size change must be forwarded to the subprocess
+  forward('SIGWINCH')
+
+  // On exit, exit this process with the same exit code
+  proc.on('close', (code: number, signal: string) => {
+    if (signal) {
+      process.kill(process.pid, signal)
+    } else if (code) {
+      process.exit(code)
+    }
   })
+
+  // If this process is exited with any other signals,
+  // kill the subprocess with the same signal
+  process.on('exit', (_code: number, signal: string) => proc.kill(signal))
 })

src/index.spec.ts

@@ -1,5 +1,5 @@
 import { expect } from 'chai'
-import { exec } from 'child_process'
+import { exec, spawn } from 'child_process'
 import { join } from 'path'
 import semver = require('semver')
 import ts = require('typescript')
@@ -20,6 +20,33 @@ describe('ts-node', function () {
   })
 
   describe('cli', function () {
+    this.slow(1000)
+
+    it('should forward signals to the child process', function (done) {
+      this.slow(5000)
+
+      const proc = spawn('node', [
+        EXEC_PATH,
+        'tests/signals'
+      ], {
+        shell: '/bin/bash'
+      })
+
+      let stdout = ''
+      proc.stdout.on('data', (data) => stdout += data.toString())
+
+      proc.on('exit', function (code) {
+        expect(code).to.equal(0)
+        expect(stdout).to.equal('exited\n')
+
+        return done()
+      })
+
+      // Leave enough time for node to fully start
+      // the process, then send a signal
+      setTimeout(() => proc.kill('SIGINT'), 1000)
+    })
+
     it('should execute cli', function (done) {
       exec(`${BIN_EXEC} tests/hello-world`, function (err, stdout) {
         expect(err).to.equal(null)

tests/signals.ts

@@ -0,0 +1,8 @@
+process.on('SIGINT', () => {
+  setTimeout(() => {
+    console.log('exited')
+    process.exit(0)
+  }, 2000)
+})
+
+setInterval(() => console.log('should not be reached'), 4000)