--modules-folder leads to broken npm install script execution

[ingobecker]

I'm unsure if this issue is related to yarn or the way the 'node-sass' package is written. I tried to run yarn install --modules-folder <some_folder> to install a package which depends on a package that tries to call node to run a npm installation script. While this works without using --modules-folder it fails while using it, as the npm install script relies on another package which can't be found at the runtime of this script as it is a dependency of this dependency installed into the custom modules folder. Invoking yarn by setting the NODE_PATH manually to the path specified by --modules-folder makes the installation script run flawlessly (NODE_PATH=<custom_path> yarn install --modules-folder <custom_path>).
I don't know if it's just bad practice of the node-sass package to rely on a packages dependency in a install script or if there is something wrong with the way yarn handles the --modules-folder option.

Following versions are used:

• yarn 1.3.2
• node v8.9.4
• debian 9.3

[witrin]

I would say node-sass package is fine. Same problem here. With an option like --modules-folder <folder> I would expect that yarn run [...] prepares the environment with <folder> so resolving packages using require just work but it does not.

[witrin]

@ingobecker But there might be a simple workaround for you. Just put the following in your .yarnrc:

--*.modules-folder <folder>
env:
  NODE_PATH "<folder>"