child_process instance set encoding will trigger exception

[hstarorg]

• Version: v9.3.0
• Platform: Darwin 16.7.0 Darwin Kernel Version 16.7.0: Thu Jan 11 22:59:40 PST 2018; root:xnu-3789.73.8~1/RELEASE_X86_64 x86_64
• Subsystem:

Execute code at node command line.

const cp = require('child_process');

const child = cp.exec('pwd', {encoding: 'invalid'}, (err, stdout, stderr) => {
  console.log('callback', err)
  console.log('callback', typeof stdout, stdout)
})

child.stdout.setEncoding('utf8')

child.stdout.on('data', function (v) {
  console.log(typeof v, v)
})

The output is :

buffer.js:475
      throw new errors.TypeError(
      ^

TypeError [ERR_INVALID_ARG_TYPE]: The "list" argument must be one of type Array, Buffer, or Uint8Array
    at Function.concat (buffer.js:475:13)
    at ChildProcess.exithandler (child_process.js:259:23)
    at ChildProcess.emit (events.js:159:13)
    at maybeClose (internal/child_process.js:943:16)
    at Socket.stream.socket.on (internal/child_process.js:363:11)
    at Socket.emit (events.js:159:13)
    at Pipe._handle.close [as _onclose] (net.js:568:12)

Is this a bug in nodejs?

BTW: The issue finder is @xqin

There didn't trigger the exception if use cp.exec('pwd', {encoding: 'invalid'}) without the callback.

@xqin has a new idea that whether need bind listener on stdout and stderr when user not pass the callback param. The source code at: https://github.com/nodejs/node/blob/master/lib/child_process.js#L322-L358

[xqin]

$ node -v
v9.3.0
$ uname -a
Darwin 16.7.0 Darwin Kernel Version 16.7.0: Thu Jan 11 22:59:40 PST 2018; root:xnu-3789.73.8~1/RELEASE_X86_64 x86_64

code

$ cat test.js
const cp = require('child_process');

const child = cp.exec('pwd', {encoding: 'invalid'}, (err, stdout, stderr) => {
  console.log('callback', err)
  console.log('callback', typeof stdout, stdout)
})

child.stdout.setEncoding('utf8')

child.stdout.on('data', function (v) {
  console.log(typeof v, v)
})

$ node test.js
string /Users/xqin

buffer.js:475
      throw new errors.TypeError(
      ^

TypeError [ERR_INVALID_ARG_TYPE]: The "list" argument must be one of type Array, Buffer, or Uint8Array
    at Function.concat (buffer.js:475:13)
    at ChildProcess.exithandler (child_process.js:259:23)
    at ChildProcess.emit (events.js:159:13)
    at maybeClose (internal/child_process.js:943:16)
    at Socket.stream.socket.on (internal/child_process.js:363:11)
    at Socket.emit (events.js:159:13)
    at Pipe._handle.close [as _onclose] (net.js:568:12)

[killagu]

It's cp bug.
cp have not checked the stdout or stderr encoding changed, cp decide by options.encoding to use stdout or Buffer.concat it.when encoding change to utf-8, the Buffer.concat will failed.

I will raise a PR to fix it.

[hstarorg]

@killagu Please see this, whether need bind listener on stdout and stderr when user not pass the callback param. The source code at: https://github.com/nodejs/node/blob/master/lib/child_process.js#L322-L358

[killagu]

@hstarorg It should in another issue. One pr resolve one problem.

[hstarorg]

@killagu OK, Thanks.