fix(core): ensure proper install for git dependency using Yarn classic and npm

[colincasey]

What's the problem this PR addresses?
When a git dependency is specified that doesn't exist in the yarn cache it will be:

• cloned to a temporary folder
• the target package manager used will be detected
• dependencies will be installed using the target package manager
• the target package manager will then execute the pack command to create a tarball that can be installed
  • if any pack lifecycle scripts exist (i.e.; prepack, postpack) these will also be executed

If a pack lifecycle script depends on dev dependencies to be installed this process can fail in cases where environment variables like the following are present:

• NODE_ENV=production (npm and Yarn classic)
• NPM_CONFIG_PRODUCTION=true (npm)

This process of creating the installable tarball should guarantee that all dependencies are available and not allow environment variables to change what is installed.

How did you fix it?
This can be fixed by removing the environment variables described above from the subprocess spawned to handle the Yarn classic and npm install steps when preparing an external project.

Checklist

• I have read the Contributing Guide.

• I have set the packages that need to be released for my changes to be effective.

• I will check that all automated PR checks pass before the PR gets reviewed.

[merceyz]

We'll also need to do this for Yarn classic as well since it has the same behaviour.

[merceyz]

Rejected to value: {"externalException": {"message": "Invalid or unexpected token"}}

That error is happening because the content of the file is

'module.exports
=
42;'

[colincasey]

thanks @merceyz. i had to add that output temporarily to understand why windows was failing with the syntax error. next commit should sort things out 😅

[merceyz]

Perfect, could you update the description to match the final state of the PR?

[merceyz]

LGTM, thanks!