Passing empty environment variables to child processes convert to 'undefined' using ConEmu + Node

[nicojs]

• Version: Since Node 8.0.0. (tested in Node 7.9, Node 8.0.0 and Node 8.2.1)
• Platform: Windows 10 version 1703 x64 using a shell (cmd.exe or git-bash) in ConEmu

Problem description

When executing a process which spawns a child process, which in turn creates another child process, the empty environment variables are passed through as 'undefined' (the string literal, NOT an absent value). If you than for example do an npm install command from that child process, bad things happen:

npm WARN invalid config access=undefined
npm WARN invalid config also=undefined
npm WARN invalid config https-proxy=undefined
npm WARN invalid config Must be a full url with \'http://\'
npm WARN onload-script     at Function.Module._resolveFilename (module.js:485:15)
npm WARN onload-script  { Error: Cannot find module \'undefined\'

To my knowledge: this only happens in ConEmu, a popular console emulator on Windows. When i downgrade to node 7.9, this problem does not occur.

Steps to reproduce

I created a small github repo to reproduce the problem.

1. On windows 10: install ConEmu: https://conemu.github.io/
2. Clone this repo git clone git@github.com:nicojs/reproduce-conemu-child-process-environment-bug.git
3. run npm install.
4. run npm test

This test spawns a child process, which in turn starts a new child process which logs the process.env to console. The tests verifies that npm_config_onload_script (one of the env variables) is set to ''.

Actual results

When ran from within ConEmu: the test failes

1. the env should contain "npm_config_onload_script":
   Error: "npm_config_onload_script": "undefined"!"

The test also prints the environment variables to screen. You can see a lot of "undefined" values (the string literal, not an absent value).

For example: "npm_config_onload_script": "undefined",

Expected results

If ran from cmd or git-bash using mintty directly (or on a POSIX environment): the test passes

√ should contain "npm_config_onload_script"

If you now look at the environment variables on screen, you don't see the "undefined" values. Just empty strings.

For example: "npm_config_onload_script": "",

I reported this issue to ConEmu first, but the developer pointed out to me that this seems to be regression in node. See the discussion with Maximus5 here: ConEmu/ConEmu#1209

Screenshots:

ConEmu with cmd.exe shell

Command prompt with cmd.exe shell

[bnoordhuis]

Thanks for the bug report. Does it reproduce outside of npm? The behavior of process.env hasn't changed between v7.x and v8.x so I expect it's caused by something in npm.

[nicojs]

I've thought of that as well, but I'm using npm 5.3.0 in all cases so that doesn't seem to be the issue.

Maybe something changed to 'child_process'? I'm using require('child_process').exec and require('child_process').execSync.

[bnoordhuis]

Can you reproduce without npm being involved? If so, can you post that test case? (It's fine to do that inline here in a comment.)

[nicojs]

Hmm good point.

Yes, I can. In one simple script using node -e.

// start.js
const execSync = require('child_process').execSync;
process.env.foobar = '';
const stdout = execSync('node -e "const execSync = require(\'child_process\').execSync;' +
    'execSync(\'node -e "console.log(process.env.foobar);"\', { stdio: [0, 1, 2]});"')
    .toString().trim();
if (stdout === '') {
    console.log('foobar is empty, stuff works.');
} else {
    console.error(`foobar was "${stdout}", using ConEmu?`);
}

If i run that script from a ConEmu tap using cmd shell it says:

> node start.js
foobar was "undefined", using ConEmu?

From command prompt and cmd.exe:

>node start.js
foobar is empty, stuff works.

[bnoordhuis]

Well, that does point to ConEmu. FWIW, it works in the expected way on Linux and OS X too.

[nicojs]

Well, that does point to ConEmu. FWIW, it works in the expected way on Linux and OS X too.

ConEmu maintainer Maximus5 says it does not change any environment variables. Also, it is translated to the actual string value 'undefined'. This seems to be something that happens in the JavaScript world.

If you change my script to print the entire environment like this:

const execSync = require('child_process').execSync;
process.env.foobar = '';
const stdout = execSync('node -e "require(\'child_process\').execSync(\'node -e "console.log(process.env);"\', { stdio: [0, 1, 2]});"')
    .toString().trim();
console.log(stdout);

If i run that script from a ConEmu tap it says:

> node start.js
...
foobar: 'undefined',
...

From cmd.exe:

>node start.js
...
foobar: undefined,
...

[bnoordhuis]

Can't reproduce, I'm afraid; it prints foobar: '', for me.

cc @nodejs/platform-windows in case any of you can reproduce.

[nicojs]

Just double checking: you have Node version 8.0.0 or 8.2.1 and running from inside ConEmu with cmd shell?

Did you let it print the entire process.env (my second inline sample)? In that case it should not print foobar: '', instead it should print foobar: undefined (but from ConEmu it prints foobar: 'undefined'). I've just tested it on an other windows 10 machine with ConEmu and was able to reproduce it using node version 8.1.2.

[tniessen]

Unable to reproduce with ConEmu 161206 (stable build) and node 8.2.1 on Windows 10. Both npm install in your repository and your snippet work just fine. Which ConEmu version are you using? How is your shell inside ConEmu configured? Please post the full shell command line along with any additional options.

[nicojs]

170402 (preview), but just now also installed 161206 and same issue.

These are my ConEmu settings, but also tried on an other laptop with default settings: https://gist.github.com/nicojs/3abd0b4b2a996c1633bd97c9fd33ec27

See this screenshot for a side by side comparison of what i'm doing. On the left you can see the content of the file "start.js" (which is the first code snippet i shared) and executed from within ConEmu. On the right site you can see the same file executed from command prompt. Also on screen is the about window of ConEmu (with the version).

EDIT:

These are my shell settings for cmd (which are default). But i can reproduce with all shells. Tested with gitbash, powershell and cmd (64bits and 32bits)

[bzoz]

@nicojs, could you provide output of env from both ConEmu and cmd.exe?

[bzoz]

And node -e console.log(process.env)?

[nicojs]

I feel slightly naked for doing this. Everything for the cause. Please don't make fun of the size of my P...ATH

https://gist.github.com/nicojs/4de5af23fa937deb8372ced562ef0878

I did the same thing on both console applications and output can be found in the gist:

> type start.js
> node start.js
> SET
> node -e "console.log(process.env)"