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

[nicojs]

Versions

ConEmu build: 170402 x64
OS version: Windows 10 version 1703 x64
Used shell version git-bash: v2.11.0

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'.

Steps to reproduce

1. Install the latest version of node&npm: http://nodejs.org/
2. Clone this repo git clone [email protected]:nicojs/reproduce-conemu-child-process-environment-bug.git
3. run npm install.
4. run npm test

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: 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": "",

Additional files

Settings,

[Maximus5]

If ran from cmd or git-bash using mintty

THIS is NOT fair comparison. ConEmu doesn't ruin node. From your screenshots I can make a conclusion you run bash. Report this to your bash bundle authors.
Third-party application problems

[Maximus5]

Also you said: it runs from cmd.
So run cmd.exe in ConEmu (as shell) and check!

[nicojs]

The same issue when running cmd.exe in ConEmu.

But not using command prompt:

The only way for me to reproduce this issue is to run it in ConEmu with any shell (cmd or git bash).

I read trough the Third-party application problems page before submitting this issue, but seeing i can only reproduce it in ConEmu, i decided to report it here.

[Maximus5]

Just checked. And...

It is working with node 7.9.0. Regression in node?

[Maximus5]

ConEmu does not change environment variables while running applications.

https://conemu.github.io/en/WindowsEnvironment.html

[nicojs]

It is working with node 7.9.0. Regression in node?

I think so yeah. I just tried it with node 7.9, works fine. Switching to node 8.0.0 seems to break it. I will open an issue at node.

[nicojs]

I'll close this issue for now, hope we can find out whats happening at Node side. Thanks for your help @Maximus5

[nicojs]

@Maximus5 it appears to be caused by an injected dll at ConEmu side: "ConEmuHq.dll"

https://github.com/nodejs/node/issues/14593#issuecomment-319676772

People are able to reproduce it in multiple node versions. Any ideas?

[refack]

@Maximus5 IMHO the edge case here is that in node we can set an empty string env var:

process.env.foobar='';

attached is a minimally reproducing script and a Procmon PML trace
conemu-1209.zip
The env var foobar get converted from an empty string to a NULL with the first spawn
In the second spawn a bug on node's side converts the js undefined value to its string representation

[nicojs]

@refack so this is an issue on node side only? Or on ConEmu side as well?

[refack]

AFAICT on both sides
ComEmu converts empty strings to null
node convert null to undefined

[Maximus5]

ConEmu doesn't change environment. And hooked GetEnvironmentVariable properly returns empty string.
But Node checks for non-zero GetLastError() instead of described ERROR_ENVVAR_NOT_FOUND.

[nicojs]

What does the ConEmuHq.dll do? Because it does change the behavior of node (regardless of the node bug)

[Maximus5]

It's all in docs: http://conemu.github.io/en/ConEmuHk.html

TL;DR - it's a required component to bypass conhost bugs and limitations.